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Kemet mil-spec cap ???
At a hamfest I picked up a bunch of what I think are axial lead tubular
metal case tantalum capacitors by Kemet. Case size B and C. I'm going to call Kemet tomorrow but in the mean time I wonder if anyone can decipher the code the capacitance and voltage. +M 39003 01-2035 7440MB 31433 JM, it measures 70 microfarads +M390003 01-2021 7452MD 31433 MW , it measures 17 microfards M390003 01-K 2017 7426MA 31433 JA, it measures 33 microfarads From the Kemet website I know that M390003 is mil-spec and the 31433 is the source code whatever that means. I think the last two letters are the date code but the 01-XXX and XXMX escape me but I'd guess it's the stuff I want to know! Any help appreciated. 73 Hank WD5JFR |
After several calls to the factory I was able to find someone who had a book on the codes. Here's what he gave me when he figured out what number was important. 2116 = 1uF @ 50V 2064 = 6.8uF @ 35V 2139 = 18uF @ 50V 2031 = 22 uF @ 15V 2017 = 33uF @ 10V 2004-J = 47uF @ 6V 2035 = 68uF @ 15V 2021 = 100uF @ 10V I've measured several on two different capacitor meters and all read close to what the factory told me. I wonder why they coded the values with numbers that don't make any sense? Military intellligence? 73 Hank WD5JFR "Henry Kolesnik" wrote in message y.com... At a hamfest I picked up a bunch of what I think are axial lead tubular metal case tantalum capacitors by Kemet. Case size B and C. I'm going to call Kemet tomorrow but in the mean time I wonder if anyone can decipher the code the capacitance and voltage. +M 39003 01-2035 7440MB 31433 JM, it measures 70 microfarads +M390003 01-2021 7452MD 31433 MW , it measures 17 microfards M390003 01-K 2017 7426MA 31433 JA, it measures 33 microfarads From the Kemet website I know that M390003 is mil-spec and the 31433 is the source code whatever that means. I think the last two letters are the date code but the 01-XXX and XXMX escape me but I'd guess it's the stuff I want to know! Any help appreciated. 73 Hank WD5JFR |
After several calls to the factory I was able to find someone who had a book on the codes. Here's what he gave me when he figured out what number was important. 2116 = 1uF @ 50V 2064 = 6.8uF @ 35V 2139 = 18uF @ 50V 2031 = 22 uF @ 15V 2017 = 33uF @ 10V 2004-J = 47uF @ 6V 2035 = 68uF @ 15V 2021 = 100uF @ 10V I've measured several on two different capacitor meters and all read close to what the factory told me. I wonder why they coded the values with numbers that don't make any sense? Military intellligence? 73 Hank WD5JFR "Henry Kolesnik" wrote in message y.com... At a hamfest I picked up a bunch of what I think are axial lead tubular metal case tantalum capacitors by Kemet. Case size B and C. I'm going to call Kemet tomorrow but in the mean time I wonder if anyone can decipher the code the capacitance and voltage. +M 39003 01-2035 7440MB 31433 JM, it measures 70 microfarads +M390003 01-2021 7452MD 31433 MW , it measures 17 microfards M390003 01-K 2017 7426MA 31433 JA, it measures 33 microfarads From the Kemet website I know that M390003 is mil-spec and the 31433 is the source code whatever that means. I think the last two letters are the date code but the 01-XXX and XXMX escape me but I'd guess it's the stuff I want to know! Any help appreciated. 73 Hank WD5JFR |
In article om,
"Henry Kolesnik" wrote: After several calls to the factory I was able to find someone who had a book on the codes. Here's what he gave me when he figured out what number was important. 2116 = 1uF @ 50V 2064 = 6.8uF @ 35V 2139 = 18uF @ 50V 2031 = 22 uF @ 15V 2017 = 33uF @ 10V 2004-J = 47uF @ 6V 2035 = 68uF @ 15V 2021 = 100uF @ 10V I've measured several on two different capacitor meters and all read close to what the factory told me. I wonder why they coded the values with numbers that don't make any sense? Military intellligence? 73 Hank WD5JFR The numbers, like 2116, are just sequencial numbers on a very large table that covers many pages in a manual. The numbers make sense when you have the manual. Al -- There's never enough time to do it right the first time....... |
In article om,
"Henry Kolesnik" wrote: After several calls to the factory I was able to find someone who had a book on the codes. Here's what he gave me when he figured out what number was important. 2116 = 1uF @ 50V 2064 = 6.8uF @ 35V 2139 = 18uF @ 50V 2031 = 22 uF @ 15V 2017 = 33uF @ 10V 2004-J = 47uF @ 6V 2035 = 68uF @ 15V 2021 = 100uF @ 10V I've measured several on two different capacitor meters and all read close to what the factory told me. I wonder why they coded the values with numbers that don't make any sense? Military intellligence? 73 Hank WD5JFR The numbers, like 2116, are just sequencial numbers on a very large table that covers many pages in a manual. The numbers make sense when you have the manual. Al -- There's never enough time to do it right the first time....... |
In article om, "Henry
Kolesnik" writes: I've measured several on two different capacitor meters and all read close to what the factory told me. I wonder why they coded the values with numbers that don't make any sense? Military intellligence? No, Hank, having a new number set to anything is the result of every manufacturer assigning THEIR own arbitrary number or letter ID to their products. The military and the government is stuck with a TOTAL variety of spare parts that can boggle the mind...and does sometimes tax the efforts of those responsible for maintaining the logistics of vital parts of EVERYTHING for our government's needs. I've been up to my elbows in Mil Specs quite enough in the past half century and just accept it as part of the environment. If you consult those Mil Specs long enough, you will see that there IS an order on ID, nomenclature, and so forth. Not only that, but aside from COTS stocks, a tantalum cap built to a certain Mil Spec will be the same value, size, rating, and shape from another manufacturer. Same with resistors, inductors, etc., etc., etc. Try that with more than one commercial component manufacturer especially when there's a production run going on and the parts supply is lagging and the parts from another manufacturer don't fit. Deep trouble time. Or one manufacturer may add on some suffix letters or numbers to a so-called "standard" part because they make an "improved line" of products and the purchasing department doesn't adjust to this other manufacture's IDs... The center for Military Intelligence schooling and operations is at Fort Huachuca, AZ. They have a website with interesting stuff on M.I. history in it. Len Anderson retired (from regular hours) electronic engineer person |
In article om, "Henry
Kolesnik" writes: I've measured several on two different capacitor meters and all read close to what the factory told me. I wonder why they coded the values with numbers that don't make any sense? Military intellligence? No, Hank, having a new number set to anything is the result of every manufacturer assigning THEIR own arbitrary number or letter ID to their products. The military and the government is stuck with a TOTAL variety of spare parts that can boggle the mind...and does sometimes tax the efforts of those responsible for maintaining the logistics of vital parts of EVERYTHING for our government's needs. I've been up to my elbows in Mil Specs quite enough in the past half century and just accept it as part of the environment. If you consult those Mil Specs long enough, you will see that there IS an order on ID, nomenclature, and so forth. Not only that, but aside from COTS stocks, a tantalum cap built to a certain Mil Spec will be the same value, size, rating, and shape from another manufacturer. Same with resistors, inductors, etc., etc., etc. Try that with more than one commercial component manufacturer especially when there's a production run going on and the parts supply is lagging and the parts from another manufacturer don't fit. Deep trouble time. Or one manufacturer may add on some suffix letters or numbers to a so-called "standard" part because they make an "improved line" of products and the purchasing department doesn't adjust to this other manufacture's IDs... The center for Military Intelligence schooling and operations is at Fort Huachuca, AZ. They have a website with interesting stuff on M.I. history in it. Len Anderson retired (from regular hours) electronic engineer person |
On Mon, 08 Mar 2004 21:44:10 GMT Al wrote:
In article om, "Henry Kolesnik" wrote: After several calls to the factory I was able to find someone who had a book on the codes. Here's what he gave me when he figured out what number was important. 2116 = 1uF @ 50V 2064 = 6.8uF @ 35V 2139 = 18uF @ 50V 2031 = 22 uF @ 15V 2017 = 33uF @ 10V 2004-J = 47uF @ 6V 2035 = 68uF @ 15V 2021 = 100uF @ 10V I've measured several on two different capacitor meters and all read close to what the factory told me. I wonder why they coded the values with numbers that don't make any sense? Military intellligence? The numbers, like 2116, are just sequencial numbers on a very large table that covers many pages in a manual. The numbers make sense when you have the manual. Okay, but why pick an identifiction method that requires a manual? Most other components this size, including theirs, just have the relevant numbers printed on them. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
On Mon, 08 Mar 2004 21:44:10 GMT Al wrote:
In article om, "Henry Kolesnik" wrote: After several calls to the factory I was able to find someone who had a book on the codes. Here's what he gave me when he figured out what number was important. 2116 = 1uF @ 50V 2064 = 6.8uF @ 35V 2139 = 18uF @ 50V 2031 = 22 uF @ 15V 2017 = 33uF @ 10V 2004-J = 47uF @ 6V 2035 = 68uF @ 15V 2021 = 100uF @ 10V I've measured several on two different capacitor meters and all read close to what the factory told me. I wonder why they coded the values with numbers that don't make any sense? Military intellligence? The numbers, like 2116, are just sequencial numbers on a very large table that covers many pages in a manual. The numbers make sense when you have the manual. Okay, but why pick an identifiction method that requires a manual? Most other components this size, including theirs, just have the relevant numbers printed on them. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
One serious shortcome of this system is that a tech in the field would have
a tough or impossible time replacing a known defective capacitor, say shorted, with the correct value without a cross reference of mil numbers vs value. The system is oxymoronic in this case as is military intelligence in many more and I served! 73 Hank WD5JFR "Avery Fineman" wrote in message ... In article om, "Henry Kolesnik" writes: I've measured several on two different capacitor meters and all read close to what the factory told me. I wonder why they coded the values with numbers that don't make any sense? Military intellligence? No, Hank, having a new number set to anything is the result of every manufacturer assigning THEIR own arbitrary number or letter ID to their products. The military and the government is stuck with a TOTAL variety of spare parts that can boggle the mind...and does sometimes tax the efforts of those responsible for maintaining the logistics of vital parts of EVERYTHING for our government's needs. I've been up to my elbows in Mil Specs quite enough in the past half century and just accept it as part of the environment. If you consult those Mil Specs long enough, you will see that there IS an order on ID, nomenclature, and so forth. Not only that, but aside from COTS stocks, a tantalum cap built to a certain Mil Spec will be the same value, size, rating, and shape from another manufacturer. Same with resistors, inductors, etc., etc., etc. Try that with more than one commercial component manufacturer especially when there's a production run going on and the parts supply is lagging and the parts from another manufacturer don't fit. Deep trouble time. Or one manufacturer may add on some suffix letters or numbers to a so-called "standard" part because they make an "improved line" of products and the purchasing department doesn't adjust to this other manufacture's IDs... The center for Military Intelligence schooling and operations is at Fort Huachuca, AZ. They have a website with interesting stuff on M.I. history in it. Len Anderson retired (from regular hours) electronic engineer person |
One serious shortcome of this system is that a tech in the field would have
a tough or impossible time replacing a known defective capacitor, say shorted, with the correct value without a cross reference of mil numbers vs value. The system is oxymoronic in this case as is military intelligence in many more and I served! 73 Hank WD5JFR "Avery Fineman" wrote in message ... In article om, "Henry Kolesnik" writes: I've measured several on two different capacitor meters and all read close to what the factory told me. I wonder why they coded the values with numbers that don't make any sense? Military intellligence? No, Hank, having a new number set to anything is the result of every manufacturer assigning THEIR own arbitrary number or letter ID to their products. The military and the government is stuck with a TOTAL variety of spare parts that can boggle the mind...and does sometimes tax the efforts of those responsible for maintaining the logistics of vital parts of EVERYTHING for our government's needs. I've been up to my elbows in Mil Specs quite enough in the past half century and just accept it as part of the environment. If you consult those Mil Specs long enough, you will see that there IS an order on ID, nomenclature, and so forth. Not only that, but aside from COTS stocks, a tantalum cap built to a certain Mil Spec will be the same value, size, rating, and shape from another manufacturer. Same with resistors, inductors, etc., etc., etc. Try that with more than one commercial component manufacturer especially when there's a production run going on and the parts supply is lagging and the parts from another manufacturer don't fit. Deep trouble time. Or one manufacturer may add on some suffix letters or numbers to a so-called "standard" part because they make an "improved line" of products and the purchasing department doesn't adjust to this other manufacture's IDs... The center for Military Intelligence schooling and operations is at Fort Huachuca, AZ. They have a website with interesting stuff on M.I. history in it. Len Anderson retired (from regular hours) electronic engineer person |
In article ,
Jim Adney wrote: On Mon, 08 Mar 2004 21:44:10 GMT Al wrote: In article om, "Henry Kolesnik" wrote: After several calls to the factory I was able to find someone who had a book on the codes. Here's what he gave me when he figured out what number was important. 2116 = 1uF @ 50V 2064 = 6.8uF @ 35V 2139 = 18uF @ 50V 2031 = 22 uF @ 15V 2017 = 33uF @ 10V 2004-J = 47uF @ 6V 2035 = 68uF @ 15V 2021 = 100uF @ 10V I've measured several on two different capacitor meters and all read close to what the factory told me. I wonder why they coded the values with numbers that don't make any sense? Military intellligence? The numbers, like 2116, are just sequencial numbers on a very large table that covers many pages in a manual. The numbers make sense when you have the manual. Okay, but why pick an identifiction method that requires a manual? Most other components this size, including theirs, just have the relevant numbers printed on them. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- OK, let me give you a few example lines from the manual: uF Case tol. Failure Rate (%/1000hrs) DC Leakage in uA Code % 1.0 0.1 0.01 0.001 25C 85C 125C 5.6 A 5 5001 5201 5401 5601 0.3 6 7.5 5.6 A 10 2241 2481 2721 2961 0.3 6 7.5 6.8 A 5 5002 5202 5402 5602 0.3 6 7.5 6.8 A 10 2242 2482 2722 2962 0.3 6 7.5 6.8 A 20 2243 2483 2723 2963 0.3 6 7.5 So a M38003/01-5001 is unique. I left out the dissipation factor for simplicty. As you can see, there is much more information in this code number than just the capacitance value and the voltage. When a component is bought to this specification, it will meet it. If you buy a random FF uF VV volt capacitor, you have no clue as to what you have with respect to leakage, reliability, dissipation factor and the like. al -- There's never enough time to do it right the first time....... |
In article ,
Jim Adney wrote: On Mon, 08 Mar 2004 21:44:10 GMT Al wrote: In article om, "Henry Kolesnik" wrote: After several calls to the factory I was able to find someone who had a book on the codes. Here's what he gave me when he figured out what number was important. 2116 = 1uF @ 50V 2064 = 6.8uF @ 35V 2139 = 18uF @ 50V 2031 = 22 uF @ 15V 2017 = 33uF @ 10V 2004-J = 47uF @ 6V 2035 = 68uF @ 15V 2021 = 100uF @ 10V I've measured several on two different capacitor meters and all read close to what the factory told me. I wonder why they coded the values with numbers that don't make any sense? Military intellligence? The numbers, like 2116, are just sequencial numbers on a very large table that covers many pages in a manual. The numbers make sense when you have the manual. Okay, but why pick an identifiction method that requires a manual? Most other components this size, including theirs, just have the relevant numbers printed on them. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- OK, let me give you a few example lines from the manual: uF Case tol. Failure Rate (%/1000hrs) DC Leakage in uA Code % 1.0 0.1 0.01 0.001 25C 85C 125C 5.6 A 5 5001 5201 5401 5601 0.3 6 7.5 5.6 A 10 2241 2481 2721 2961 0.3 6 7.5 6.8 A 5 5002 5202 5402 5602 0.3 6 7.5 6.8 A 10 2242 2482 2722 2962 0.3 6 7.5 6.8 A 20 2243 2483 2723 2963 0.3 6 7.5 So a M38003/01-5001 is unique. I left out the dissipation factor for simplicty. As you can see, there is much more information in this code number than just the capacitance value and the voltage. When a component is bought to this specification, it will meet it. If you buy a random FF uF VV volt capacitor, you have no clue as to what you have with respect to leakage, reliability, dissipation factor and the like. al -- There's never enough time to do it right the first time....... |
On Tue, 09 Mar 2004 14:28:56 GMT Al wrote:
In article , Jim Adney wrote: Okay, but why pick an identifiction method that requires a manual? Most other components this size, including theirs, just have the relevant numbers printed on them. OK, let me give you a few example lines from the manual: uF Case tol. Failure Rate (%/1000hrs) DC Leakage in uA Code % 1.0 0.1 0.01 0.001 25C 85C 125C 5.6 A 5 5001 5201 5401 5601 0.3 6 7.5 5.6 A 10 2241 2481 2721 2961 0.3 6 7.5 6.8 A 5 5002 5202 5402 5602 0.3 6 7.5 6.8 A 10 2242 2482 2722 2962 0.3 6 7.5 6.8 A 20 2243 2483 2723 2963 0.3 6 7.5 So a M38003/01-5001 is unique. I left out the dissipation factor for simplicty. As you can see, there is much more information in this code number than just the capacitance value and the voltage. When a component is bought to this specification, it will meet it. If you buy a random FF uF VV volt capacitor, you have no clue as to what you have with respect to leakage, reliability, dissipation factor and the like. I have a similar page here from the Sprague/Vishay catalog. In this case it just happens to be for some caps which I picked up surplus which are marked M39006/25-xxxx. In this case the xxxx code pins down the tolerance and failure rate, just as the Kemet does above (note that everything else above is the same.) OTOH, the Sprague/Vishay caps are also labeled with their C and V ratings, as well as the tolerance. Only the failure rate is left unexplained. There is also an H-code for high vibration which you might need the catalog page to interpret. BTW, both manufacturers have a code for an M failure rate, which is 1.0% per 1000 hours. I find it hard to believe that anyone would buy such a device, especially the military. The ones I got were the R rate, .01% per 1000 hours. Those are the best that they offer and I'll bet those are the only ones that ever get sold. So I still don't think it's too much to ask that the most important data be printed out separately. Obviously, I don't tend to think like the military.... - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
On Tue, 09 Mar 2004 14:28:56 GMT Al wrote:
In article , Jim Adney wrote: Okay, but why pick an identifiction method that requires a manual? Most other components this size, including theirs, just have the relevant numbers printed on them. OK, let me give you a few example lines from the manual: uF Case tol. Failure Rate (%/1000hrs) DC Leakage in uA Code % 1.0 0.1 0.01 0.001 25C 85C 125C 5.6 A 5 5001 5201 5401 5601 0.3 6 7.5 5.6 A 10 2241 2481 2721 2961 0.3 6 7.5 6.8 A 5 5002 5202 5402 5602 0.3 6 7.5 6.8 A 10 2242 2482 2722 2962 0.3 6 7.5 6.8 A 20 2243 2483 2723 2963 0.3 6 7.5 So a M38003/01-5001 is unique. I left out the dissipation factor for simplicty. As you can see, there is much more information in this code number than just the capacitance value and the voltage. When a component is bought to this specification, it will meet it. If you buy a random FF uF VV volt capacitor, you have no clue as to what you have with respect to leakage, reliability, dissipation factor and the like. I have a similar page here from the Sprague/Vishay catalog. In this case it just happens to be for some caps which I picked up surplus which are marked M39006/25-xxxx. In this case the xxxx code pins down the tolerance and failure rate, just as the Kemet does above (note that everything else above is the same.) OTOH, the Sprague/Vishay caps are also labeled with their C and V ratings, as well as the tolerance. Only the failure rate is left unexplained. There is also an H-code for high vibration which you might need the catalog page to interpret. BTW, both manufacturers have a code for an M failure rate, which is 1.0% per 1000 hours. I find it hard to believe that anyone would buy such a device, especially the military. The ones I got were the R rate, .01% per 1000 hours. Those are the best that they offer and I'll bet those are the only ones that ever get sold. So I still don't think it's too much to ask that the most important data be printed out separately. Obviously, I don't tend to think like the military.... - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
Jim Adney wrote:
. . . So I still don't think it's too much to ask that the most important data be printed out separately. Obviously, I don't tend to think like the military.... - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- While you've got a legitimate point, you've got to realize the function of the part number. If you're a technician servicing a piece of military gear, you replace a 20035942 *ONLY* with a 20035942, not *ANY* other capacitor, regardless of its value. To order a replacement, you put in a requisition for a 20035942. Now, it's vital to you that the capacitors in the stock bin or coming in from the supply system have 20035942 printed on them, but it's not important that the value is. The technician can find the value in the parts list in the manual and likely on the schematic. The stark fact is that the military supply system wasn't created and isn't maintained for the convenience of the ham who's working on surplus gear. You'll actually find this is true throughout the industry, with many ICs, for example, having only the customer's part numbers on them. Go to a flea market anywhere around here where I live, and you'll find lots of components with only Tektronix part numbers on them. You'll also find lots of folks locally who can tell you what they are, at least generically. I'm sure the same thing is true for HP and Palo Alto, Motorola and Phoenix, and so forth. It's not that you don't think like the military -- it's just that when they developed their stock system they didn't take into consideration the inconvenience it would cause you, me, and other hobbyists. Roy Lewallen, W7EL |
Jim Adney wrote:
. . . So I still don't think it's too much to ask that the most important data be printed out separately. Obviously, I don't tend to think like the military.... - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- While you've got a legitimate point, you've got to realize the function of the part number. If you're a technician servicing a piece of military gear, you replace a 20035942 *ONLY* with a 20035942, not *ANY* other capacitor, regardless of its value. To order a replacement, you put in a requisition for a 20035942. Now, it's vital to you that the capacitors in the stock bin or coming in from the supply system have 20035942 printed on them, but it's not important that the value is. The technician can find the value in the parts list in the manual and likely on the schematic. The stark fact is that the military supply system wasn't created and isn't maintained for the convenience of the ham who's working on surplus gear. You'll actually find this is true throughout the industry, with many ICs, for example, having only the customer's part numbers on them. Go to a flea market anywhere around here where I live, and you'll find lots of components with only Tektronix part numbers on them. You'll also find lots of folks locally who can tell you what they are, at least generically. I'm sure the same thing is true for HP and Palo Alto, Motorola and Phoenix, and so forth. It's not that you don't think like the military -- it's just that when they developed their stock system they didn't take into consideration the inconvenience it would cause you, me, and other hobbyists. Roy Lewallen, W7EL |
I was a GCA radar tech in the RCAF in the 1960s and in one of the excercises
(war games) we had to find and fix a fault so the incoming aircraft wouldn't crash, it was zero visibility . Sometimes it was as easy as a bad or loose tube, but some seargents had subchassis with cold solder joints, shorted black beauty capacitors or fried resistors. Time was critcal as the weather was closing fast and the aircraft was low on fuel. Sometimes the excercise left us without many parts, partially functional test equpt, and only partial manuals. To better simulate battle conditions, one end of the hut could be on fire and CO2 smoke to hinder visibilty! A shorted .01 uF 400VDC black beauty was easliy replaced with a .01 uF 600VDC or .02 a fried 22K 1/2 watt with a 22K 2 watt or something close. Color codes were quite useful in many cases. The objective was to save the aircraft using limited resources. Today I don't think we see component level repair in the field but in battle anything may be necessary for survival. I'd much rather have something with component values rather than a bunch of codes that required decifering. I still contend this is a result of "military intelligence." And the codes make it tough on us hobbyists but we not under a critical time crunch and with the Internet it's usually a piece of cake. 73 Hank WD5JFR "Roy Lewallen" wrote in message ... Jim Adney wrote: . . . So I still don't think it's too much to ask that the most important data be printed out separately. Obviously, I don't tend to think like the military.... - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- While you've got a legitimate point, you've got to realize the function of the part number. If you're a technician servicing a piece of military gear, you replace a 20035942 *ONLY* with a 20035942, not *ANY* other capacitor, regardless of its value. To order a replacement, you put in a requisition for a 20035942. Now, it's vital to you that the capacitors in the stock bin or coming in from the supply system have 20035942 printed on them, but it's not important that the value is. The technician can find the value in the parts list in the manual and likely on the schematic. The stark fact is that the military supply system wasn't created and isn't maintained for the convenience of the ham who's working on surplus gear. You'll actually find this is true throughout the industry, with many ICs, for example, having only the customer's part numbers on them. Go to a flea market anywhere around here where I live, and you'll find lots of components with only Tektronix part numbers on them. You'll also find lots of folks locally who can tell you what they are, at least generically. I'm sure the same thing is true for HP and Palo Alto, Motorola and Phoenix, and so forth. It's not that you don't think like the military -- it's just that when they developed their stock system they didn't take into consideration the inconvenience it would cause you, me, and other hobbyists. Roy Lewallen, W7EL |
I was a GCA radar tech in the RCAF in the 1960s and in one of the excercises
(war games) we had to find and fix a fault so the incoming aircraft wouldn't crash, it was zero visibility . Sometimes it was as easy as a bad or loose tube, but some seargents had subchassis with cold solder joints, shorted black beauty capacitors or fried resistors. Time was critcal as the weather was closing fast and the aircraft was low on fuel. Sometimes the excercise left us without many parts, partially functional test equpt, and only partial manuals. To better simulate battle conditions, one end of the hut could be on fire and CO2 smoke to hinder visibilty! A shorted .01 uF 400VDC black beauty was easliy replaced with a .01 uF 600VDC or .02 a fried 22K 1/2 watt with a 22K 2 watt or something close. Color codes were quite useful in many cases. The objective was to save the aircraft using limited resources. Today I don't think we see component level repair in the field but in battle anything may be necessary for survival. I'd much rather have something with component values rather than a bunch of codes that required decifering. I still contend this is a result of "military intelligence." And the codes make it tough on us hobbyists but we not under a critical time crunch and with the Internet it's usually a piece of cake. 73 Hank WD5JFR "Roy Lewallen" wrote in message ... Jim Adney wrote: . . . So I still don't think it's too much to ask that the most important data be printed out separately. Obviously, I don't tend to think like the military.... - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- While you've got a legitimate point, you've got to realize the function of the part number. If you're a technician servicing a piece of military gear, you replace a 20035942 *ONLY* with a 20035942, not *ANY* other capacitor, regardless of its value. To order a replacement, you put in a requisition for a 20035942. Now, it's vital to you that the capacitors in the stock bin or coming in from the supply system have 20035942 printed on them, but it's not important that the value is. The technician can find the value in the parts list in the manual and likely on the schematic. The stark fact is that the military supply system wasn't created and isn't maintained for the convenience of the ham who's working on surplus gear. You'll actually find this is true throughout the industry, with many ICs, for example, having only the customer's part numbers on them. Go to a flea market anywhere around here where I live, and you'll find lots of components with only Tektronix part numbers on them. You'll also find lots of folks locally who can tell you what they are, at least generically. I'm sure the same thing is true for HP and Palo Alto, Motorola and Phoenix, and so forth. It's not that you don't think like the military -- it's just that when they developed their stock system they didn't take into consideration the inconvenience it would cause you, me, and other hobbyists. Roy Lewallen, W7EL |
In article om,
"Henry Kolesnik" wrote: I was a GCA radar tech in the RCAF in the 1960s and in one of the excercises (war games) we had to find and fix a fault so the incoming aircraft wouldn't crash, it was zero visibility . Sometimes it was as easy as a bad or loose tube, but some seargents had subchassis with cold solder joints, shorted black beauty capacitors or fried resistors. Time was critcal as the weather was closing fast and the aircraft was low on fuel. Sometimes the excercise left us without many parts, partially functional test equpt, and only partial manuals. To better simulate battle conditions, one end of the hut could be on fire and CO2 smoke to hinder visibilty! A shorted .01 uF 400VDC black beauty was easliy replaced with a .01 uF 600VDC or .02 a fried 22K 1/2 watt with a 22K 2 watt or something close. Color codes were quite useful in many cases. The objective was to save the aircraft using limited resources. Today I don't think we see component level repair in the field but in battle anything may be necessary for survival. I'd much rather have something with component values rather than a bunch of codes that required decifering. I still contend this is a result of "military intelligence." And the codes make it tough on us hobbyists but we not under a critical time crunch and with the Internet it's usually a piece of cake. In the sixties that was possible. But now you can't really fly by the seat of your pants. Repair is by replacing LRUs (Least Replaceable Units). Even if the LRU makes it back to the depot for failure confirmation, it may not be repairable. 6, 8 or 12 layer PCBs cannot be readily repaired. And would you trust one that was repaired if it did not go through a burn-in cycle afterward? Would you depend on a fail-safe circuit to prevent a nuclear launch if it had a component replaced in it that was "close enough?" Maybe in your cars brake system, but not on my missile! Al -- There's never enough time to do it right the first time....... |
In article om,
"Henry Kolesnik" wrote: I was a GCA radar tech in the RCAF in the 1960s and in one of the excercises (war games) we had to find and fix a fault so the incoming aircraft wouldn't crash, it was zero visibility . Sometimes it was as easy as a bad or loose tube, but some seargents had subchassis with cold solder joints, shorted black beauty capacitors or fried resistors. Time was critcal as the weather was closing fast and the aircraft was low on fuel. Sometimes the excercise left us without many parts, partially functional test equpt, and only partial manuals. To better simulate battle conditions, one end of the hut could be on fire and CO2 smoke to hinder visibilty! A shorted .01 uF 400VDC black beauty was easliy replaced with a .01 uF 600VDC or .02 a fried 22K 1/2 watt with a 22K 2 watt or something close. Color codes were quite useful in many cases. The objective was to save the aircraft using limited resources. Today I don't think we see component level repair in the field but in battle anything may be necessary for survival. I'd much rather have something with component values rather than a bunch of codes that required decifering. I still contend this is a result of "military intelligence." And the codes make it tough on us hobbyists but we not under a critical time crunch and with the Internet it's usually a piece of cake. In the sixties that was possible. But now you can't really fly by the seat of your pants. Repair is by replacing LRUs (Least Replaceable Units). Even if the LRU makes it back to the depot for failure confirmation, it may not be repairable. 6, 8 or 12 layer PCBs cannot be readily repaired. And would you trust one that was repaired if it did not go through a burn-in cycle afterward? Would you depend on a fail-safe circuit to prevent a nuclear launch if it had a component replaced in it that was "close enough?" Maybe in your cars brake system, but not on my missile! Al -- There's never enough time to do it right the first time....... |
"Al" wrote in message ... In article om, "Henry Kolesnik" wrote: I was a GCA radar tech in the RCAF in the 1960s and in one of the excercises (war games) we had to find and fix a fault so the incoming aircraft wouldn't crash, it was zero visibility . Sometimes it was as easy as a bad or loose tube, but some seargents had subchassis with cold solder joints, shorted black beauty capacitors or fried resistors. Time was critcal as the weather was closing fast and the aircraft was low on fuel. Sometimes the excercise left us without many parts, partially functional test equpt, and only partial manuals. To better simulate battle conditions, one end of the hut could be on fire and CO2 smoke to hinder visibilty! A shorted .01 uF 400VDC black beauty was easliy replaced with a .01 uF 600VDC or .02 a fried 22K 1/2 watt with a 22K 2 watt or something close. Color codes were quite useful in many cases. The objective was to save the aircraft using limited resources. Today I don't think we see component level repair in the field but in battle anything may be necessary for survival. I'd much rather have something with component values rather than a bunch of codes that required decifering. I still contend this is a result of "military intelligence." And the codes make it tough on us hobbyists but we not under a critical time crunch and with the Internet it's usually a piece of cake. In the sixties that was possible. But now you can't really fly by the seat of your pants. Repair is by replacing LRUs (Least Replaceable Units). Even if the LRU makes it back to the depot for failure confirmation, it may not be repairable. 6, 8 or 12 layer PCBs cannot be readily repaired. And would you trust one that was repaired if it did not go through a burn-in cycle afterward? Would you depend on a fail-safe circuit to prevent a nuclear launch if it had a component replaced in it that was "close enough?" Maybe in your cars brake system, but not on my missile! True, in the 'close enough' stakes, but it is well worth reflecting that 90% of simple systems use a relatively small 'subset' of parts from the avilable world pool. An engineer, with one each of the IC's for a range of boards, and a few dozen resistors and capacitors, can potentially repair most faults on such boards 'on site', especially if the board is designed with this in mind (possibly with some form of self diagnostics for many parts). However if the same units are built with SM parts in quantity, using custom IC's, the solution becomes to carry a complete replacement board. Doing this for a few dozen products is often not practical. The problem here is that the custom IC/SM solution is cheaper once production reaches a reasonable level, but is not the best solution where the units are going to be a long way from 'spares'. I designed a range of units used on sites across many third-world countries, and it became necessary to deliberately design the units with both redundancy, and repairability in mind. Given that the service engineer may have to travel 1000miles to get to a unit, having it so that repair is likely to be possible, was a vital design criterion. The parts list was deliberately 'shrunk', retaining as far as was practical a limited range of parts used in all. Unfortunately the relative costs of truly 'mass' production, combined with robot construction/assembly, make such designs a 'dying art'... Best Wishes |
"Al" wrote in message ... In article om, "Henry Kolesnik" wrote: I was a GCA radar tech in the RCAF in the 1960s and in one of the excercises (war games) we had to find and fix a fault so the incoming aircraft wouldn't crash, it was zero visibility . Sometimes it was as easy as a bad or loose tube, but some seargents had subchassis with cold solder joints, shorted black beauty capacitors or fried resistors. Time was critcal as the weather was closing fast and the aircraft was low on fuel. Sometimes the excercise left us without many parts, partially functional test equpt, and only partial manuals. To better simulate battle conditions, one end of the hut could be on fire and CO2 smoke to hinder visibilty! A shorted .01 uF 400VDC black beauty was easliy replaced with a .01 uF 600VDC or .02 a fried 22K 1/2 watt with a 22K 2 watt or something close. Color codes were quite useful in many cases. The objective was to save the aircraft using limited resources. Today I don't think we see component level repair in the field but in battle anything may be necessary for survival. I'd much rather have something with component values rather than a bunch of codes that required decifering. I still contend this is a result of "military intelligence." And the codes make it tough on us hobbyists but we not under a critical time crunch and with the Internet it's usually a piece of cake. In the sixties that was possible. But now you can't really fly by the seat of your pants. Repair is by replacing LRUs (Least Replaceable Units). Even if the LRU makes it back to the depot for failure confirmation, it may not be repairable. 6, 8 or 12 layer PCBs cannot be readily repaired. And would you trust one that was repaired if it did not go through a burn-in cycle afterward? Would you depend on a fail-safe circuit to prevent a nuclear launch if it had a component replaced in it that was "close enough?" Maybe in your cars brake system, but not on my missile! True, in the 'close enough' stakes, but it is well worth reflecting that 90% of simple systems use a relatively small 'subset' of parts from the avilable world pool. An engineer, with one each of the IC's for a range of boards, and a few dozen resistors and capacitors, can potentially repair most faults on such boards 'on site', especially if the board is designed with this in mind (possibly with some form of self diagnostics for many parts). However if the same units are built with SM parts in quantity, using custom IC's, the solution becomes to carry a complete replacement board. Doing this for a few dozen products is often not practical. The problem here is that the custom IC/SM solution is cheaper once production reaches a reasonable level, but is not the best solution where the units are going to be a long way from 'spares'. I designed a range of units used on sites across many third-world countries, and it became necessary to deliberately design the units with both redundancy, and repairability in mind. Given that the service engineer may have to travel 1000miles to get to a unit, having it so that repair is likely to be possible, was a vital design criterion. The parts list was deliberately 'shrunk', retaining as far as was practical a limited range of parts used in all. Unfortunately the relative costs of truly 'mass' production, combined with robot construction/assembly, make such designs a 'dying art'... Best Wishes |
In article 2HI3c.3458$re1.1290@newsfe1-win,
"Roger Hamlett" wrote: "Al" wrote in message ... In article om, "Henry Kolesnik" wrote: I was a GCA radar tech in the RCAF in the 1960s and in one of the excercises (war games) we had to find and fix a fault so the incoming aircraft wouldn't crash, it was zero visibility . Sometimes it was as easy as a bad or loose tube, but some seargents had subchassis with cold solder joints, shorted black beauty capacitors or fried resistors. Time was critcal as the weather was closing fast and the aircraft was low on fuel. Sometimes the excercise left us without many parts, partially functional test equpt, and only partial manuals. To better simulate battle conditions, one end of the hut could be on fire and CO2 smoke to hinder visibilty! A shorted .01 uF 400VDC black beauty was easliy replaced with a .01 uF 600VDC or .02 a fried 22K 1/2 watt with a 22K 2 watt or something close. Color codes were quite useful in many cases. The objective was to save the aircraft using limited resources. Today I don't think we see component level repair in the field but in battle anything may be necessary for survival. I'd much rather have something with component values rather than a bunch of codes that required decifering. I still contend this is a result of "military intelligence." And the codes make it tough on us hobbyists but we not under a critical time crunch and with the Internet it's usually a piece of cake. In the sixties that was possible. But now you can't really fly by the seat of your pants. Repair is by replacing LRUs (Least Replaceable Units). Even if the LRU makes it back to the depot for failure confirmation, it may not be repairable. 6, 8 or 12 layer PCBs cannot be readily repaired. And would you trust one that was repaired if it did not go through a burn-in cycle afterward? Would you depend on a fail-safe circuit to prevent a nuclear launch if it had a component replaced in it that was "close enough?" Maybe in your cars brake system, but not on my missile! True, in the 'close enough' stakes, but it is well worth reflecting that 90% of simple systems use a relatively small 'subset' of parts from the avilable world pool. An engineer, with one each of the IC's for a range of boards, and a few dozen resistors and capacitors, can potentially repair most faults on such boards 'on site', especially if the board is designed with this in mind (possibly with some form of self diagnostics for many parts). However if the same units are built with SM parts in quantity, using custom IC's, the solution becomes to carry a complete replacement board. Doing this for a few dozen products is often not practical. The problem here is that the custom IC/SM solution is cheaper once production reaches a reasonable level, but is not the best solution where the units are going to be a long way from 'spares'. I designed a range of units used on sites across many third-world countries, and it became necessary to deliberately design the units with both redundancy, and repairability in mind. Given that the service engineer may have to travel 1000miles to get to a unit, having it so that repair is likely to be possible, was a vital design criterion. The parts list was deliberately 'shrunk', retaining as far as was practical a limited range of parts used in all. Unfortunately the relative costs of truly 'mass' production, combined with robot construction/assembly, make such designs a 'dying art'... Best Wishes If your design criterion is that the equipment be field repairable with readily available parts, then so be it. I have no argument with that! But in the high-reliability military electronics world in which I worked in the late 60's, that was not possible. Would you believe that one printed circuit card, 4 in by 6 in, was needed just to implement 4 flip-flops using descrete components. Each component, yes even a carbon composition resistor, had a serial number on it. Why? So it could be traced back to the lot from it which it had been selected if it failed. And boy, did those components have to be reliable! So that's why the military specifications with their "strange" component markings were invented. Expensive? Lordy, lordy! I was very shocked one day when I requisitioned a capacitor from stock to compare to a rejected one. The price for that unit, a precision paper mylar cap. was $100 - in 1970's dollars! I almost fell out of my chair! And now you can buy stuff like that, surplus, for just pennies on the dollar...and with their strange markings. I have a bag full of CSR13G825KR's! Anybody need one? Al Al -- There's never enough time to do it right the first time....... |
In article 2HI3c.3458$re1.1290@newsfe1-win,
"Roger Hamlett" wrote: "Al" wrote in message ... In article om, "Henry Kolesnik" wrote: I was a GCA radar tech in the RCAF in the 1960s and in one of the excercises (war games) we had to find and fix a fault so the incoming aircraft wouldn't crash, it was zero visibility . Sometimes it was as easy as a bad or loose tube, but some seargents had subchassis with cold solder joints, shorted black beauty capacitors or fried resistors. Time was critcal as the weather was closing fast and the aircraft was low on fuel. Sometimes the excercise left us without many parts, partially functional test equpt, and only partial manuals. To better simulate battle conditions, one end of the hut could be on fire and CO2 smoke to hinder visibilty! A shorted .01 uF 400VDC black beauty was easliy replaced with a .01 uF 600VDC or .02 a fried 22K 1/2 watt with a 22K 2 watt or something close. Color codes were quite useful in many cases. The objective was to save the aircraft using limited resources. Today I don't think we see component level repair in the field but in battle anything may be necessary for survival. I'd much rather have something with component values rather than a bunch of codes that required decifering. I still contend this is a result of "military intelligence." And the codes make it tough on us hobbyists but we not under a critical time crunch and with the Internet it's usually a piece of cake. In the sixties that was possible. But now you can't really fly by the seat of your pants. Repair is by replacing LRUs (Least Replaceable Units). Even if the LRU makes it back to the depot for failure confirmation, it may not be repairable. 6, 8 or 12 layer PCBs cannot be readily repaired. And would you trust one that was repaired if it did not go through a burn-in cycle afterward? Would you depend on a fail-safe circuit to prevent a nuclear launch if it had a component replaced in it that was "close enough?" Maybe in your cars brake system, but not on my missile! True, in the 'close enough' stakes, but it is well worth reflecting that 90% of simple systems use a relatively small 'subset' of parts from the avilable world pool. An engineer, with one each of the IC's for a range of boards, and a few dozen resistors and capacitors, can potentially repair most faults on such boards 'on site', especially if the board is designed with this in mind (possibly with some form of self diagnostics for many parts). However if the same units are built with SM parts in quantity, using custom IC's, the solution becomes to carry a complete replacement board. Doing this for a few dozen products is often not practical. The problem here is that the custom IC/SM solution is cheaper once production reaches a reasonable level, but is not the best solution where the units are going to be a long way from 'spares'. I designed a range of units used on sites across many third-world countries, and it became necessary to deliberately design the units with both redundancy, and repairability in mind. Given that the service engineer may have to travel 1000miles to get to a unit, having it so that repair is likely to be possible, was a vital design criterion. The parts list was deliberately 'shrunk', retaining as far as was practical a limited range of parts used in all. Unfortunately the relative costs of truly 'mass' production, combined with robot construction/assembly, make such designs a 'dying art'... Best Wishes If your design criterion is that the equipment be field repairable with readily available parts, then so be it. I have no argument with that! But in the high-reliability military electronics world in which I worked in the late 60's, that was not possible. Would you believe that one printed circuit card, 4 in by 6 in, was needed just to implement 4 flip-flops using descrete components. Each component, yes even a carbon composition resistor, had a serial number on it. Why? So it could be traced back to the lot from it which it had been selected if it failed. And boy, did those components have to be reliable! So that's why the military specifications with their "strange" component markings were invented. Expensive? Lordy, lordy! I was very shocked one day when I requisitioned a capacitor from stock to compare to a rejected one. The price for that unit, a precision paper mylar cap. was $100 - in 1970's dollars! I almost fell out of my chair! And now you can buy stuff like that, surplus, for just pennies on the dollar...and with their strange markings. I have a bag full of CSR13G825KR's! Anybody need one? Al Al -- There's never enough time to do it right the first time....... |
In article , Al
writes: If your design criterion is that the equipment be field repairable with readily available parts, then so be it. I have no argument with that! But in the high-reliability military electronics world in which I worked in the late 60's, that was not possible. In the late 1960s I was working in both commercial, space, and military electronics. Only the space electronics (unmanned space- craft done at Electro-Optical Systems, EOS, in Pasadena, CA, a Xerox division) was there traceability to that extent, plus the "JAN TX" or tested-extra solid-state components. That was with reasonable logic since no company would pay per diem for in-the-field space- craft repairpersons... :-) I might note that the little labels used to mark the components were of a selected brand...to avoid outgassing in vacuum of space and thus coating some other spacecraft instrument or sensor. Some have called such a practice "braindead procedures by NASA" but those people are themselves braindead for not thinking through for operating in a very different environment. Since that time I've been involved in a lot of other DoD electronics and have never seen that level of traceability except in certain prototypes and then used solely for development testing. NASA man-rating specs - not Mil Specs unless called out for common types - required screening and traceability for a very good reason that humans were aboard those spacecraft (STS or "shuttle"). Astronauts shouldn't be required to get down to the PCB level and unsolder bad components and resolder new ones in microgravity for one reason. Another reason is that they can't GET to a part such as the ignitor of an SSME (Space Shuttle Main Engine, built at Rocketdyne Division of Rockwell International in Canoga Park, CA, - now a division of Boeing Aircraft). That ignitor was often called a "spark plug" in-house but was really a redundant astable multivibrator turned on remotely and a driver for an external arc gap...the entire "ignition system" in one extremely clean (had to work in pure oxygen environment) little unit that had to work just fine in vibration you couldn't possibly imagine. Much military radio and electronics equipment bears something resembling screening markings on modules but any research into that will show they are merely in-house or depot markings for ID and other things, not traceability. If you see the insides of an AN/PRC-104 HF transceiver or an AN/PRC-119 VHF FHSS transceiver, you will see what I'm talking about. Would you believe that one printed circuit card, 4 in by 6 in, was needed just to implement 4 flip-flops using descrete components. That's not at all strange for the late 1960s. Integrated circuits weren't there to use, and had only begun to be Mil Specced. Those were new from Texas Instruments and still the old DTL or Diode-Transistor-Logic. The IBM 360 and RCA Spectra 70 used discrete-transistor PCBs in the 1970s. IBM didn't go into TTL ICs in a large way until the IBM 370 VM and production starting around 1975. Each component, yes even a carbon composition resistor, had a serial number on it. Why? So it could be traced back to the lot from it which it had been selected if it failed. And boy, did those components have to be reliable! So that's why the military specifications with their "strange" component markings were invented. Expensive? Lordy, lordy! I was very shocked one day when I requisitioned a capacitor from stock to compare to a rejected one. The price for that unit, a precision paper mylar cap. was $100 - in 1970's dollars! I almost fell out of my chair! And now you can buy stuff like that, surplus, for just pennies on the dollar...and with their strange markings. I'm going to challenge the veracity of that claim due to "having been there, done that," and only seeing that in NASA electronics. Also, I have yet to see any "surplus" spacecraft, including the engineering and test models that never flew. Back in 1974 I and a co-worker were stuck in Galveston, TX, for an RCA Corporation field test. We visited the Manned Space Flight Center in nearby Clear Lake and did a walking tour on a Sunday, unescorted as was the norm on Sundays there. I wanted to show the friend the Solar Wind Spectrometer instrument built for the ALSEP (Apollo Lunar Surface Experiment Package) in 1967. I had handled all of the SWSs when they were built. All of the ALSEP modules - except the SWS - were arranged around the "left-over" Landing and Ascent stages in the lobby. I snagged a docent and asked about the "missing" instrument. She went off and returned, said "sorry, it is still being used in a lab experiment." Seven years later and it was still working...after having gone through some tough environmental testing on earth. NASA manned or unmanned electronics is subject to the maximum in traceability. Military fielded electronics has had traceability limited to specific lots identified through records and specified percentage sampling tests on those lots. Samples may be tested to destruction depending on the Mil Specification. All that TESTING effort is what drives the parts cost up AND having to package spares in extra-special protection envelopes and containers since they may be sitting waiting in some terrible environment somewhere in the world. World War 2 production and logistics taught the U.S. military much about needing spares and how to ship and store everything. USA has always been darn good about logistics and supply and has been successful at it. To those folks who want to sneer at "military intelligence," fine. Nobody is forcing them to like military electronics or the military. Let them build things for room-temperature environments using surplus CB radio parts or those from TV sets. However, when those also sneer at little things like nomenclature about high quality stuff available surplus at cut rate, it does warrant a strong response. Roy Lewallen had the succinct response. :-) Len Anderson retired (from regular hours) electronic engineer person |
In article , Al
writes: If your design criterion is that the equipment be field repairable with readily available parts, then so be it. I have no argument with that! But in the high-reliability military electronics world in which I worked in the late 60's, that was not possible. In the late 1960s I was working in both commercial, space, and military electronics. Only the space electronics (unmanned space- craft done at Electro-Optical Systems, EOS, in Pasadena, CA, a Xerox division) was there traceability to that extent, plus the "JAN TX" or tested-extra solid-state components. That was with reasonable logic since no company would pay per diem for in-the-field space- craft repairpersons... :-) I might note that the little labels used to mark the components were of a selected brand...to avoid outgassing in vacuum of space and thus coating some other spacecraft instrument or sensor. Some have called such a practice "braindead procedures by NASA" but those people are themselves braindead for not thinking through for operating in a very different environment. Since that time I've been involved in a lot of other DoD electronics and have never seen that level of traceability except in certain prototypes and then used solely for development testing. NASA man-rating specs - not Mil Specs unless called out for common types - required screening and traceability for a very good reason that humans were aboard those spacecraft (STS or "shuttle"). Astronauts shouldn't be required to get down to the PCB level and unsolder bad components and resolder new ones in microgravity for one reason. Another reason is that they can't GET to a part such as the ignitor of an SSME (Space Shuttle Main Engine, built at Rocketdyne Division of Rockwell International in Canoga Park, CA, - now a division of Boeing Aircraft). That ignitor was often called a "spark plug" in-house but was really a redundant astable multivibrator turned on remotely and a driver for an external arc gap...the entire "ignition system" in one extremely clean (had to work in pure oxygen environment) little unit that had to work just fine in vibration you couldn't possibly imagine. Much military radio and electronics equipment bears something resembling screening markings on modules but any research into that will show they are merely in-house or depot markings for ID and other things, not traceability. If you see the insides of an AN/PRC-104 HF transceiver or an AN/PRC-119 VHF FHSS transceiver, you will see what I'm talking about. Would you believe that one printed circuit card, 4 in by 6 in, was needed just to implement 4 flip-flops using descrete components. That's not at all strange for the late 1960s. Integrated circuits weren't there to use, and had only begun to be Mil Specced. Those were new from Texas Instruments and still the old DTL or Diode-Transistor-Logic. The IBM 360 and RCA Spectra 70 used discrete-transistor PCBs in the 1970s. IBM didn't go into TTL ICs in a large way until the IBM 370 VM and production starting around 1975. Each component, yes even a carbon composition resistor, had a serial number on it. Why? So it could be traced back to the lot from it which it had been selected if it failed. And boy, did those components have to be reliable! So that's why the military specifications with their "strange" component markings were invented. Expensive? Lordy, lordy! I was very shocked one day when I requisitioned a capacitor from stock to compare to a rejected one. The price for that unit, a precision paper mylar cap. was $100 - in 1970's dollars! I almost fell out of my chair! And now you can buy stuff like that, surplus, for just pennies on the dollar...and with their strange markings. I'm going to challenge the veracity of that claim due to "having been there, done that," and only seeing that in NASA electronics. Also, I have yet to see any "surplus" spacecraft, including the engineering and test models that never flew. Back in 1974 I and a co-worker were stuck in Galveston, TX, for an RCA Corporation field test. We visited the Manned Space Flight Center in nearby Clear Lake and did a walking tour on a Sunday, unescorted as was the norm on Sundays there. I wanted to show the friend the Solar Wind Spectrometer instrument built for the ALSEP (Apollo Lunar Surface Experiment Package) in 1967. I had handled all of the SWSs when they were built. All of the ALSEP modules - except the SWS - were arranged around the "left-over" Landing and Ascent stages in the lobby. I snagged a docent and asked about the "missing" instrument. She went off and returned, said "sorry, it is still being used in a lab experiment." Seven years later and it was still working...after having gone through some tough environmental testing on earth. NASA manned or unmanned electronics is subject to the maximum in traceability. Military fielded electronics has had traceability limited to specific lots identified through records and specified percentage sampling tests on those lots. Samples may be tested to destruction depending on the Mil Specification. All that TESTING effort is what drives the parts cost up AND having to package spares in extra-special protection envelopes and containers since they may be sitting waiting in some terrible environment somewhere in the world. World War 2 production and logistics taught the U.S. military much about needing spares and how to ship and store everything. USA has always been darn good about logistics and supply and has been successful at it. To those folks who want to sneer at "military intelligence," fine. Nobody is forcing them to like military electronics or the military. Let them build things for room-temperature environments using surplus CB radio parts or those from TV sets. However, when those also sneer at little things like nomenclature about high quality stuff available surplus at cut rate, it does warrant a strong response. Roy Lewallen had the succinct response. :-) Len Anderson retired (from regular hours) electronic engineer person |
On Tue, 09 Mar 2004 19:59:19 -0800 Roy Lewallen
wrote: Jim Adney wrote: . . . So I still don't think it's too much to ask that the most important data be printed out separately. Obviously, I don't tend to think like the military.... While you've got a legitimate point, you've got to realize the function of the part number. If you're a technician servicing a piece of military gear, you replace a 20035942 *ONLY* with a 20035942, not *ANY* other capacitor, regardless of its value. To order a replacement, you put in a requisition for a 20035942. Now, it's vital to you that the capacitors in the stock bin or coming in from the supply system have 20035942 printed on them, but it's not important that the value is. The technician can find the value in the parts list in the manual and likely on the schematic. If I'm that tech, how do I correlate that p/n with this cap on the schematic? Does the schematic have both the value AND the p/n on it? I understand your point about using the exact replacement, but I don't see why a part should not have BOTH sets of data. To me, that seems like it adds a lot of value to the part. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
On Tue, 09 Mar 2004 19:59:19 -0800 Roy Lewallen
wrote: Jim Adney wrote: . . . So I still don't think it's too much to ask that the most important data be printed out separately. Obviously, I don't tend to think like the military.... While you've got a legitimate point, you've got to realize the function of the part number. If you're a technician servicing a piece of military gear, you replace a 20035942 *ONLY* with a 20035942, not *ANY* other capacitor, regardless of its value. To order a replacement, you put in a requisition for a 20035942. Now, it's vital to you that the capacitors in the stock bin or coming in from the supply system have 20035942 printed on them, but it's not important that the value is. The technician can find the value in the parts list in the manual and likely on the schematic. If I'm that tech, how do I correlate that p/n with this cap on the schematic? Does the schematic have both the value AND the p/n on it? I understand your point about using the exact replacement, but I don't see why a part should not have BOTH sets of data. To me, that seems like it adds a lot of value to the part. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
Jim Adney wrote:
If I'm that tech, how do I correlate that p/n with this cap on the schematic? Does the schematic have both the value AND the p/n on it? I understand your point about using the exact replacement, but I don't see why a part should not have BOTH sets of data. To me, that seems like it adds a lot of value to the part. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- Typically, the schematic will identify the part by "circuit number", say C143 (and might or might not show the value), and it'll be on page A4B3, which is the schematic for board B3 in larger assembly A4. In the same manual, there'll be a parts list for A4B3, where you can find the description of C143, along with its part number. It would certainly include the value, type, and probably the tolerance, which are important to know when troubleshooting. Sometimes it'll tell a little more, if there's something particularly unusual about the part. But the full description of that part #20035942 only appears on a document that's typically many pages long and fully describes its specifications. There might be 100 different part numbers for 4.7 uF, 10%, 50 volt tantalum capacitors, each with different specifications for reliability testing, temperature range, ESR, mechanical lead strength, vibration tolerance, tada, tada, tada. They are *NOT* interchangeable in the military or commercial environment. Substitution could result in failure at a critical time or place with incredibly expensive, disastrous, or fatal consequences. When replacing the part, the only thing that's important to the technician is whether the replacement has the right part number. If it doesn't, the part doesn't go in, regardless of what its capacitance value might be. Yep, stamping the value on the capacitor would undoubtedly add value to the part for you and me. But again, the military just wasn't thinking of us when it set up its stock system. Roy Lewallen, W7EL |
Jim Adney wrote:
If I'm that tech, how do I correlate that p/n with this cap on the schematic? Does the schematic have both the value AND the p/n on it? I understand your point about using the exact replacement, but I don't see why a part should not have BOTH sets of data. To me, that seems like it adds a lot of value to the part. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- Typically, the schematic will identify the part by "circuit number", say C143 (and might or might not show the value), and it'll be on page A4B3, which is the schematic for board B3 in larger assembly A4. In the same manual, there'll be a parts list for A4B3, where you can find the description of C143, along with its part number. It would certainly include the value, type, and probably the tolerance, which are important to know when troubleshooting. Sometimes it'll tell a little more, if there's something particularly unusual about the part. But the full description of that part #20035942 only appears on a document that's typically many pages long and fully describes its specifications. There might be 100 different part numbers for 4.7 uF, 10%, 50 volt tantalum capacitors, each with different specifications for reliability testing, temperature range, ESR, mechanical lead strength, vibration tolerance, tada, tada, tada. They are *NOT* interchangeable in the military or commercial environment. Substitution could result in failure at a critical time or place with incredibly expensive, disastrous, or fatal consequences. When replacing the part, the only thing that's important to the technician is whether the replacement has the right part number. If it doesn't, the part doesn't go in, regardless of what its capacitance value might be. Yep, stamping the value on the capacitor would undoubtedly add value to the part for you and me. But again, the military just wasn't thinking of us when it set up its stock system. Roy Lewallen, W7EL |
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In fact, it's becoming much less common to find parts in commercial
equipment with only the OEM user's part number rather than the manufacturer's PN on them. Partly this is being driven by contract manufacturing of the boards, but it was a trend even before CM became so common, in my experience. Roy's comments about military techs are slightly idealistic, if I relate things to my personal experience some years ago. My shop supervisor at a remote site quickly learned to trust my judgement in finding ways to get things repaired and functioning reliably when parts simply weren't available. When it comes to a decision between completing a critical mission using a part that gets you through the mission, and waiting six months for a part, guess which wins. You can find info about some of that sort of thing on the NASA web site. Astronauts don't wait for delivery of XPQ1453762 if their lives (or even an expensive experiment) can be saved by using something on hand. Clearly, you'd prefer to use the exact part specified, or a documented replacement, but there are lots of times when waiting for that would be very poor judgement. (Darwin award candidates??) OTOH, do NOT expect modern parts to be fully labeled. Don't expect 0.1% SMT resistors to have anything on them telling you that they are 0.1%. Don't expect 0603 and smaller resistors and capacitors to have ANY marking, though some do. Don't expect SOT-23 and SC-70 parts to have anything but a simple 2 or 3 character code on them. Some (most?) SMT tantalum cap manufacturers don't seem to put a marking on them that tells you which series they are (std ESR, low ESR, extra-low ESR, fused, mil-spec...). And count your blessings that you're dealing with electronic parts, where labelling with the value is pretty common. That's not the case with most mechanical parts, for example. Would you expect Honda pistons to fit any Toyota engines? Have you ever seen ANY springs labelled with their spring constant, let alone any of their other parameters? Most aren't even labelled with a part number. Finally, there IS a reason that schematics don't always have values or manufacturer's part numbers on them, or even house part numbers, but only a reference designator. That's because values (and therefore the part numbers) may well change over time. It's a lot easier and less error-prone to maintain only one changing document: the material list used to build the board. Not everyone agrees with that, and in fact I do prefer to have values and mfgr's part numbers on my schematics. Cheers, Tom Jim Adney wrote in message . .. On Tue, 09 Mar 2004 19:59:19 -0800 Roy Lewallen wrote: Jim Adney wrote: . . . So I still don't think it's too much to ask that the most important data be printed out separately. Obviously, I don't tend to think like the military.... While you've got a legitimate point, you've got to realize the function of the part number. If you're a technician servicing a piece of military gear, you replace a 20035942 *ONLY* with a 20035942, not *ANY* other capacitor, regardless of its value. To order a replacement, you put in a requisition for a 20035942. Now, it's vital to you that the capacitors in the stock bin or coming in from the supply system have 20035942 printed on them, but it's not important that the value is. The technician can find the value in the parts list in the manual and likely on the schematic. If I'm that tech, how do I correlate that p/n with this cap on the schematic? Does the schematic have both the value AND the p/n on it? I understand your point about using the exact replacement, but I don't see why a part should not have BOTH sets of data. To me, that seems like it adds a lot of value to the part. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
In fact, it's becoming much less common to find parts in commercial
equipment with only the OEM user's part number rather than the manufacturer's PN on them. Partly this is being driven by contract manufacturing of the boards, but it was a trend even before CM became so common, in my experience. Roy's comments about military techs are slightly idealistic, if I relate things to my personal experience some years ago. My shop supervisor at a remote site quickly learned to trust my judgement in finding ways to get things repaired and functioning reliably when parts simply weren't available. When it comes to a decision between completing a critical mission using a part that gets you through the mission, and waiting six months for a part, guess which wins. You can find info about some of that sort of thing on the NASA web site. Astronauts don't wait for delivery of XPQ1453762 if their lives (or even an expensive experiment) can be saved by using something on hand. Clearly, you'd prefer to use the exact part specified, or a documented replacement, but there are lots of times when waiting for that would be very poor judgement. (Darwin award candidates??) OTOH, do NOT expect modern parts to be fully labeled. Don't expect 0.1% SMT resistors to have anything on them telling you that they are 0.1%. Don't expect 0603 and smaller resistors and capacitors to have ANY marking, though some do. Don't expect SOT-23 and SC-70 parts to have anything but a simple 2 or 3 character code on them. Some (most?) SMT tantalum cap manufacturers don't seem to put a marking on them that tells you which series they are (std ESR, low ESR, extra-low ESR, fused, mil-spec...). And count your blessings that you're dealing with electronic parts, where labelling with the value is pretty common. That's not the case with most mechanical parts, for example. Would you expect Honda pistons to fit any Toyota engines? Have you ever seen ANY springs labelled with their spring constant, let alone any of their other parameters? Most aren't even labelled with a part number. Finally, there IS a reason that schematics don't always have values or manufacturer's part numbers on them, or even house part numbers, but only a reference designator. That's because values (and therefore the part numbers) may well change over time. It's a lot easier and less error-prone to maintain only one changing document: the material list used to build the board. Not everyone agrees with that, and in fact I do prefer to have values and mfgr's part numbers on my schematics. Cheers, Tom Jim Adney wrote in message . .. On Tue, 09 Mar 2004 19:59:19 -0800 Roy Lewallen wrote: Jim Adney wrote: . . . So I still don't think it's too much to ask that the most important data be printed out separately. Obviously, I don't tend to think like the military.... While you've got a legitimate point, you've got to realize the function of the part number. If you're a technician servicing a piece of military gear, you replace a 20035942 *ONLY* with a 20035942, not *ANY* other capacitor, regardless of its value. To order a replacement, you put in a requisition for a 20035942. Now, it's vital to you that the capacitors in the stock bin or coming in from the supply system have 20035942 printed on them, but it's not important that the value is. The technician can find the value in the parts list in the manual and likely on the schematic. If I'm that tech, how do I correlate that p/n with this cap on the schematic? Does the schematic have both the value AND the p/n on it? I understand your point about using the exact replacement, but I don't see why a part should not have BOTH sets of data. To me, that seems like it adds a lot of value to the part. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
On Thu, 11 Mar 2004 00:43:21 -0800 Roy Lewallen
wrote: Yep, stamping the value on the capacitor would undoubtedly add value to the part for you and me. But again, the military just wasn't thinking of us when it set up its stock system. I was thinking of the value it would have to the tech, in helping him to make sure that the part he was looking at on the schematic and the part that he was replacing in the circuit were the same item. If he has to trace the item from the schematic (C437) to the parts list (M390009/xxxx) to the chassis (M390009/xxxx) that's an extra step where time is wasted and a mistake could be made. Both would be counterproductive, in any environment. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
On Thu, 11 Mar 2004 00:43:21 -0800 Roy Lewallen
wrote: Yep, stamping the value on the capacitor would undoubtedly add value to the part for you and me. But again, the military just wasn't thinking of us when it set up its stock system. I was thinking of the value it would have to the tech, in helping him to make sure that the part he was looking at on the schematic and the part that he was replacing in the circuit were the same item. If he has to trace the item from the schematic (C437) to the parts list (M390009/xxxx) to the chassis (M390009/xxxx) that's an extra step where time is wasted and a mistake could be made. Both would be counterproductive, in any environment. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
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