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Computer Grade
I keep seeing caps described as "computer grade" but a search for a
definition comes up with zilch. What does this mean? As the vast majority of computers are owned by the masses, one could assume it means sleazy consumer quality. Or it could mean the kind of computer that prevents ICBM's from being accidentally launched. Which is it? JACK K9ACT -- PHOTO OF THE WEEK: http://schmidling.com/pow.htm Astronomy, Beer, Cheese, Fiber,Gems, Sausage,Silver http://schmidling.com |
Computer Grade
Jack Schmidling wrote:
I keep seeing caps described as "computer grade" but a search for a definition comes up with zilch. What does this mean? As the vast majority of computers are owned by the masses, one could assume it means sleazy consumer quality. Or it could mean the kind of computer that prevents ICBM's from being accidentally launched. Which is it? JACK K9ACT The name has been around for much longer than PC's, so I assume that it means _mainframe_ computer grade -- today we'd say "server grade", I guess. At any rate, if it has no legal meaning then it could be a total lie and no one would be subject to any legal penalties (marketplace penalties are another matter). I have always taken it to mean _really_ _good_, but you'd have to go over the specs to see, then extend some trust to the manufacturer. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/ Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" gives you just what it says. See details at http://www.wescottdesign.com/actfes/actfes.html |
Computer Grade
On Mon, 30 Apr 2007 06:28:17 -0600, Jack Schmidling wrote:
What does this mean? Not a lot. It is just one of those meaningless terms like military spec. This is what passes for 'computer grade' these days: http://www.badcaps.net/ident/ 73, Ed. EI9GQ. -- Linux 2.6.18 |
Computer Grade
Jack Schmidling ) writes:
I keep seeing caps described as "computer grade" but a search for a definition comes up with zilch. What does this mean? As the vast majority of computers are owned by the masses, one could assume it means sleazy consumer quality. Or it could mean the kind of computer that prevents ICBM's from being accidentally launched. The term was around in the early seventies, at least. That was when solid state was still relatively new, and electrolytics were not as advanced as nowadays. I built 1A power supply in the fall of 1972, and had found at a hamfest a "computer grade" electrolytic, in a metal can,10,000uF at about 20 volts. It was about the size of a Coke can. It was pretty massive in terms of capacitance at the time, the regular electrolyitics were hard to find in such large values, and even this one was barely sufficient in terms of voltage rating. It was obviously surplus, from mainframe computers. I have no clue whether they were particularly better than the regular electrolyitics, but they were obviously the source for larger value filter caps at the time. I'm sure some of it was merely hype, at the very least "computer grade" says where the capacitors came from. It's obviously different now. I can easily get 10,000uF electrolytics in a far smaller package and with a bigger voltage rating. I haven't evne noticed the term in a long time, other than the occasional question about the term (it has come up before here or in one of the sci.electronics.* newsgroups. There obviously are different grades of electrolytics, with things like temperature rating being important in some applications, and ESR being important in others (especially things like switching supplies where they have to deal with higher frequency waveforms). But the talk is in terms of their specs, rather than some mythical "computer grade" capacitor. Michael VE2BVW |
Computer Grade
"Jack Schmidling" wrote in message ... I keep seeing caps described as "computer grade" but a search for a definition comes up with zilch. What does this mean? As the vast majority of computers are owned by the masses, one could assume it means sleazy consumer quality. Or it could mean the kind of computer that prevents ICBM's from being accidentally launched. Which is it? JACK K9ACT I first ran into computer grade caps back in the 1970's, back when I was building my first homebuilt computer (before the masses owned computers), I considered it a pejorative, in that it was only good for building power supplies for computers. Would it be be better if it said low voltage dc power supply caps? Those big coke can sized caps made great smoothing caps, along with some smaller caps they could knock ripple down to where you needed an oscope to see it. Just don't build a supply with that as the only cap on the output, they are ok on low freq swings, but also add a 1k and 10 uf cap to help clean up the rest of the ripple. thanks John. KC5DWD |
Computer Grade
On Mon, 30 Apr 2007 06:28:17 -0600, Jack Schmidling
wrote: I keep seeing caps described as "computer grade" but a search for a definition comes up with zilch. In the 1960/70's computers were the only application requiring very low voltage stabilised DC power supplies, +5 V for TTL, +6 V for DTL and -5.2 V for ECL. Other high power DC applications in those days, such as industrial automation, used 24 V, but relays weren't sensitive to ripple or voltage variations. When a typical computer consumed several kW at 5/6 V, quite huge DC currents were required and thus the power supply capacitance in linear power supplies had to be huge. I have seen this "computer grade" term used in the 1970's when some surplus companies tried to sell some huge size capacitors, when physically smaller capacitors became available with the same capacitance, in order to justify the size of the surplus units. But after the 1970's I have never seen the term "computer grade" used. Paul OH3LWR |
Computer Grade
In article ,
Jack Schmidling wrote: I keep seeing caps described as "computer grade" but a search for a definition comes up with zilch. What does this mean? As the vast majority of computers are owned by the masses, one could assume it means sleazy consumer quality. Or it could mean the kind of computer that prevents ICBM's from being accidentally launched. Which is it? Digging out the 1968 Newark catalog, on page 332 are the Mallory CG series of big can capacitors in a section titled "Computer Grade Electrolytic Capacitors". ie -10+75% tolerance, -40/+85 deg C temp. $10 was a lot for a capacitor in 1968. Mark Zenier Googleproofaddress(account:mzenier provider:eskimo domain:com) |
Computer Grade
"Paul Keinanen" wrote in message ... On Mon, 30 Apr 2007 06:28:17 -0600, Jack Schmidling wrote: I keep seeing caps described as "computer grade" but a search for a definition comes up with zilch. In the 1960/70's computers were the only application requiring very low voltage stabilised DC power supplies, +5 V for TTL, +6 V for DTL and -5.2 V for ECL. Other high power DC applications in those days, such as industrial automation, used 24 V, but relays weren't sensitive to ripple or voltage variations. When a typical computer consumed several kW at 5/6 V, quite huge DC currents were required and thus the power supply capacitance in linear power supplies had to be huge. I have seen this "computer grade" term used in the 1970's when some surplus companies tried to sell some huge size capacitors, when physically smaller capacitors became available with the same capacitance, in order to justify the size of the surplus units. But after the 1970's I have never seen the term "computer grade" used. Paul OH3LWR The term "computer grade" is in use today. See http://www.mouser.com/catalog/629/576.pdf and http://www.mouser.com/catalog/629/574.pdf for examples of those currently manufactured by Vishay/Sprague and Mallory/CDE. I suspect that the term "computer grade" signifies capacitors with screw terminals. However, I can't prove it. Cheers, John |
Computer Grade
"Computer Grade Capacitor" might possibly refer to the low value of internal
series resistance and inductance which are important parameters in switching regulator power supplies. Bill W0IYH "Mark Zenier" wrote in message ... In article , Jack Schmidling wrote: I keep seeing caps described as "computer grade" but a search for a definition comes up with zilch. What does this mean? As the vast majority of computers are owned by the masses, one could assume it means sleazy consumer quality. Or it could mean the kind of computer that prevents ICBM's from being accidentally launched. Which is it? Digging out the 1968 Newark catalog, on page 332 are the Mallory CG series of big can capacitors in a section titled "Computer Grade Electrolytic Capacitors". ie -10+75% tolerance, -40/+85 deg C temp. $10 was a lot for a capacitor in 1968. Mark Zenier Googleproofaddress(account:mzenier provider:eskimo domain:com) |
Computer Grade
William E. Sabin wrote:
"Computer Grade Capacitor" might possibly refer to the low value of internal series resistance and inductance which are important parameters in switching regulator power supplies. Well, maybe "low inductance" by 1960's standards. A computer power supply would have to filter 60Hz, or maybe 400Hz ripple then. Yes, there were switching supplies back in the 60's/70's too, but then switching frequencies were much much lower (think about it: they used 2N3055's or their predecessors, transistors that take a millenium to turn off!) than typical switching supplies today. Modern low-ESR low-inductance caps are undoubtedly superior if you're designing 150kHz switching supplies today. Heck, many of the modern regulator chips will only be stable if they are operated into capacitors that have an ESR above a minimum and below a maximum number. There's a reason why there are 87 different 220uF 6.3V capacitors in the Digikey catalog :-). Clearly for their purposes, surplus 2N3055's and old big-can "computer grade capacitors" can be put to very good use in many ham power supplies. Make sure you get some LM723's too, a very versatile part that modern parts (each good in their own narrow niche) have not completely replaced yet! (I did lament here on Usenet when the CA3046 was discontinued a year or two ago... a shame! But the LM723 will outlive it!) Tim. |
Computer Grade
On 5 May 2007 04:32:02 -0700, Tim Shoppa
wrote: William E. Sabin wrote: "Computer Grade Capacitor" might possibly refer to the low value of internal series resistance and inductance which are important parameters in switching regulator power supplies. Well, maybe "low inductance" by 1960's standards. A computer power supply would have to filter 60Hz, or maybe 400Hz ripple then. Apart from aviation, the last time the last time I heard someone using 400 Hz for powering computers was in the early 1960's with a 50/400 Hz motor/generator in the basement, feeding the anode supply of some tube computers :-), in order to reduce the transformer and filter capacity size. Yes, there were switching supplies back in the 60's/70's too, but then switching frequencies were much much lower (think about it: they used 2N3055's or their predecessors, transistors that take a millenium to turn off!) than typical switching supplies today. Outside TV EHT generators, primary switching power supplies were rare in those days, simply because bipolars could not handle the rectified mains voltage in those days, not at least with any significant current, so linear power supplies was the norm in those days. Clearly for their purposes, surplus 2N3055's and old big-can "computer grade capacitors" can be put to very good use in many ham power supplies. Make sure you get some LM723's too, a very versatile part that modern parts (each good in their own narrow niche) have not completely replaced yet! My guess is that amateur radio is the last application in which linear power supplies are used, since it is much easier to make a low noise linear power supply than a switcher. Paul OH3LWR |
Computer Grade
From: Paul Keinanen on Sat, 05 May 2007 18:35:57
+0300 On 5 May 2007 04:32:02 -0700, Tim Shoppa wrote: William E. Sabin wrote: "Computer Grade Capacitor" might possibly refer to the low value of internal series resistance and inductance which are important parameters in switching regulator power supplies. Well, maybe "low inductance" by 1960's standards. A computer power supply would have to filter 60Hz, or maybe 400Hz ripple then. Apart from aviation, the last time the last time I heard someone using 400 Hz for powering computers was in the early 1960's with a 50/400 Hz motor/generator in the basement, feeding the anode supply of some tube computers :-), in order to reduce the transformer and filter capacity size. Large electrolytics labeled "computer grade" were quite common in low- voltage supplies required for digital electronics from the early 1960s and into the next three decades. Once the TTL family of digital ICs "took off" all digital electronics seemed to require 5 VDC supplies. :-) Since the early TTLs were - relatively speaking - power-hungry, the supply current had to be much higher than for old tube architecture equipment. With that was the requirement for filtering the raw DC from (nearly-always) full-wave rectification resulting in 120 Hz ripple. The end result was a market need for higher-Farad electrolytics. Low-ESR in those large-capacity electrolytics was, in my opinion, less of a problem for switchers than it was to cut down on the internal heat dissipated by the ripple current in that ESR. Yes, there were switching supplies back in the 60's/70's too, but then switching frequencies were much much lower (think about it: they used 2N3055's or their predecessors, transistors that take a millenium to turn off!) than typical switching supplies today. Outside TV EHT generators, primary switching power supplies were rare in those days, simply because bipolars could not handle the rectified mains voltage in those days, not at least with any significant current, so linear power supplies was the norm in those days. I agree with that, Paul. The switch-mode supplies did not increase in either market quantity or acceptance in OEM equipment until the late 1970s. One frequently-overlooked example is the small supply (a switcher) used in the Apple ][ personal computer. Well over a quarter million made and sold to power a small computer using (then) legacy TTL devices. While some CP/M-based PCs existed using switching supplies, other PC makers saw the advantage and started using switchers also, even the "IBM" that became the norm for PCs after 1980. While most switching supplies were still radiating RFI into the late 1990s, that did not trouble PCs operation. After multi- millions of PCs have been made with switchers for power supplies in over two decades, it would seem (to many) that "switchers have always been used." :-) Clearly for their purposes, surplus 2N3055's and old big-can "computer grade capacitors" can be put to very good use in many ham power supplies. Make sure you get some LM723's too, a very versatile part that modern parts (each good in their own narrow niche) have not completely replaced yet! My guess is that amateur radio is the last application in which linear power supplies are used, since it is much easier to make a low noise linear power supply than a switcher. Much SIMPLER. :-) Today a typical under-1-Ampere supply consists of an AC transformer, bridge rectifier, one filter capacitor, and one three- terminal regulator. Positive or negative polarity, no real change in components. Guaranteed voltage regulation and the legacy three- terminal regulator ("7805" for +5 VDC output) has over-current shut- down. Spec sheets on three-terminal regulators include maximum internal noise generation (very low) which few bother to notice. :-) Excess power dissipation in a linear regulator? Actually not much. A typical +5 VDC supply for 0.5 A uses a typical 8.5 V average raw DC input and a three-terminal regulator drops about 3.5 V average for a 1.75 W average loss converted to heat. The TO-220 cases of three-terminal regulators are built to handle that (and a bit more) if mounted to a "heat sink" of copper-one-side PCB. Three-terminal regulators are entering their fourth decade of existance and couldn't be more convenient to use for a defined, regulated output voltage. 73, Len AF6AY |
Computer Grade
Yes, that genius Bob Widlar lives on through the products he designed.
http://www.sfgate.com/cgi-bin/articl...01/BU36634.DTL "Tim Shoppa" wrote in message oups.com... William E. Sabin wrote: [snip] (I did lament here on Usenet when the CA3046 was discontinued a year or two ago... a shame! But the LM723 will outlive it!) Tim. |
Computer Grade
Paul Keinanen wrote:
Apart from aviation, the last time the last time I heard someone using 400 Hz for powering computers was in the early 1960's with a 50/400 Hz motor/generator in the basement, feeding the anode supply of some tube computers :-), in order to reduce the transformer and filter capacity size. MG Sets (400 Hz) powered many mainframe and midrange systems well through the late 1970s; CDC's small graphics system called 'GRID' used a mini (2500KVA) 400 Hz MG set and it was built with TTL and DTL, and the entire 1604, 3000, 6000, 7000 and most Cybers used large MG sets. The 160/160A/ 8090 series could be equipped with 400 Hz (MG driven) supplies or 60 Hz switchers (circa 1959-1966). Regards, Michael |
Computer Grade
On Apr 30, 5:28 am, Jack Schmidling wrote:
I keep seeing caps described as "computer grade" but a search for a definition comes up with zilch. What does this mean? As the vast majority of computers are owned by the masses, one could assume it means sleazy consumer quality. Or it could mean the kind of computer that prevents ICBM's from being accidentally launched. Which is it? JACK K9ACT -- PHOTO OF THE WEEK:http://schmidling.com/pow.htm Astronomy, Beer, Cheese, Fiber,Gems, Sausage,Silverhttp://schmidling.com It is the working grade. Rated duty cycle. There are commercial - 8 hours in 24 industrial - 12 hours in 24 computer or telephone grade 24 hours in 24. The MTBF data is determined using the appropriate duty cycle. See ITT Handbook for more info. Kirk |
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