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Hammarlund HX-50 choke question.
Does anyone have a guess what value choke L112 found here
http://www.ppinyot.com/hammarlund.ht...Supply%20Choke might be? I am getting a 190 ac volt drop across this puppy. It has a cold DC resistance of 97 ohms. How I got there is also explained at the hyperlink page above. The short of it is, the negative bias voltages are down across all associated tubes that share that supply. Google is no help. Even a guess at this point would be nice. I have never calculated a choke in this configuration before. Paul P |
Hammarlund HX-50 choke question.
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PP |
Hammarlund HX-50 choke question.
"Paul P" wrote in message news:PerCh.3042$vu2.1488@trnddc04... Does anyone have a guess what value choke L112 found here http://www.ppinyot.com/hammarlund.ht...Supply%20Choke might be? I am getting a 190 ac volt drop across this puppy. It has a cold DC resistance of 97 ohms. How I got there is also explained at the hyperlink page above. The short of it is, the negative bias voltages are down across all associated tubes that share that supply. Google is no help. Even a guess at this point would be nice. I have never calculated a choke in this configuration before. Paul P Just some thinking out loud (or maybe its finger thinking). 1, Problems with chokes are usually either open windings, shorted windings, or shorts to the case or core. Open windings result in very high resistance or a completely open circuit. Shorted windings result in lower than normal DC resistance and lower than normal inductance. Shorts to the case or core can be checked with an ohm meter. One can also get high resistance "shorts" resulting in leakage from winding to core. This is best tested using a special very high resistance ohm meter. In any case, it does not sound like you are having any of these problems. The HX-50 appears to have three supplies, a high voltage supply using the 5R4 rectifier with plates connected to the outer windings of the xfmr, a low voltage supply using the silicon diodes connected to the inner windings, and a negative or bias supply using a single silicon diode (CR-106) connected to the tap on the winding. If your bias voltages are down but the B+ voltages are about normal I would suspect the bias supply. Its possible the diode is bad but they usually go either all the way open or all the way shorted. A multimeter will check it. I am more suspicious of the filter capacitors, C-176, C-177. Its also possible that something has happened to R-168, the current limiting resistor, or, perhaps one of the other resistors. I wonder if anyone has a cross-reference between Hammarlund part numbers and their specifications. I ran across a web site that has a cross-reference between "old" and "new" H part numbers, perhaps there is somesort of catalogue there. I haven't looked. It would be useful to know the inductance of L-112 and its DC resistance. The inductance being off would also be an indicator of problem. Again, if its the bias supply that has the problem I think the choke is a red herring. -- --- Richard Knoppow Los Angeles, CA, USA -- Posted via a free Usenet account from http://www.teranews.com |
Hammarlund HX-50 choke question.
Paul P wrote:
Does anyone have a guess what value choke L112 found here http://www.ppinyot.com/hammarlund.ht...Supply%20Choke might be? I am getting a 190 ac volt drop across this puppy. It has a cold DC resistance of 97 ohms. How I got there is also explained at the hyperlink page above. The short of it is, the negative bias voltages are down across all associated tubes that share that supply. Google is no help. Even a guess at this point would be nice. I have never calculated a choke in this configuration before. The choke has AC going through it, since it's on the input side of the rectifier. My guess is that it's not just a normal choke but is a swinging choke with a controlled saturation characteristic. It's acting as a current regulator; as current rises the magnetic flux in the core rises and at some point the core saturates and the impedance of the winding shoots way up, reducing the current flow. A 190V drop across it might be normal, or it might be a sign you are trying to pull way too much current through the thing. What voltages do you measure across C162 sections A and B? They should be fairly close to the maximum capacitor ratings, I suspect. If they are within a reasonable range, I'd say the swinging choke is fine, otherwise I'd suspect something is on the secondary side is pulling too much current and it's hit the wall. If it IS failed, Peter Dahl can probably rebuild it. You won't be able to just drop in something off the shelf, and sadly design of saturable reactors and magnetic controls and amplifiers is a lost art today. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
Hammarlund HX-50 choke question.
Scott Dorsey wrote:
Paul P wrote: Does anyone have a guess what value choke L112 found here http://www.ppinyot.com/hammarlund.ht...Supply%20Choke might be? I am getting a 190 ac volt drop across this puppy. It has a cold DC resistance of 97 ohms. How I got there is also explained at the hyperlink page above. The short of it is, the negative bias voltages are down across all associated tubes that share that supply. Google is no help. Even a guess at this point would be nice. I have never calculated a choke in this configuration before. The choke has AC going through it, since it's on the input side of the rectifier. My guess is that it's not just a normal choke but is a swinging choke with a controlled saturation characteristic. It's acting as a current regulator; as current rises the magnetic flux in the core rises and at some point the core saturates and the impedance of the winding shoots way up, reducing the current flow. But that is exactly backwards from the way chokes work. As the current rises, and the core approaches saturation, the coil starts to lose the inductance enhancement provided by the core, and it approaches the inductance of an equivalent air core choke. That is, the inductance *drops*, and the inductive reactance *drops* and the AC current shoots way up. -Chuck |
Hammarlund HX-50 choke question.
Paul P wrote:
Does anyone have a guess what value choke L112 found here http://www.ppinyot.com/hammarlund.ht...Supply%20Choke might be? I am getting a 190 ac volt drop across this puppy. It has a cold DC resistance of 97 ohms. How I got there is also explained at the hyperlink page above. The short of it is, the negative bias voltages are down across all associated tubes that share that supply. Google is no help. Hi, I checked the L112 choke in my HX-50, and it is 75 Ohms d.c. resistance. That is in the ball park of your 97 Ohms measurement. That same choke also serves as the high voltage choke, since it is in the common center tap return for the medium voltage and H.V. taps as well as the bias tap. In standby, I measure 195 VAC across the choke. So, it sounds like your choke is innocent of the low bias readings. Have you put a scope across the bias supply capacitors C176 and C177? They may need changing out if there is excessive ripple. The 680 Ohm resistor in series with the bias supply may have increased value. Did you check the value of R142 and bias adjust pot R143? They may be dragging down the bias voltage. You might measure the bias voltage with the 6DQ5 final tube removed. If the tube is gassy, it would tend to put a + voltage on its control grid, which may be working backward in your bias supply, making the supply less negative. 73, Ed Knobloch |
Hammarlund HX-50 choke question.
On Feb 20, 9:39�am, (Scott Dorsey) wrote:
Paul P wrote: Does anyone have a guess what value choke L112 found here http://www.ppinyot.com/hammarlund.ht...Supply%20Choke might be? *I am getting a 190 ac volt drop across this puppy. *It has a cold DC resistance of 97 ohms. *How I got there is also explained at the hyperlink page above. I doubt very much that L112 is faulty. The bias supply capacitors, rectifier and resistors are much more likely to be bad. The short of it is, the negative bias voltages are down across all associated tubes that share that supply. * Even a guess at this point would be nice. *I have never calculated a choke in this configuration before. The choke has AC going through it, since it's on the input side of the rectifier. * No, it doesn't. It has pulsating rectified DC going through it. There are two reasons why it is in the center tap lead: 1) All the power supplies can share it 2) Insulation requirements are less. My guess is that it's not just a normal choke but is a swinging choke with a controlled saturation characteristic. Agreed. *It's acting as a current regulator; as current rises the magnetic flux in the core rises and at some point the core saturates and the impedance of the winding shoots way up, reducing the current flow. Not exactly. In a choke-input filter, the inductance must be above a certain critical value or the filter isn't really a choke-input filter. This critical value (called critical inductance) is directly related to the total load resistance. The lower the load resistance, the less inductance is needed. The load resistance is just the output voltage divided by the total current delivered by the rectifiers. In a transmitter, the load resistance and current vary all over the place with keying, modulation, loading, etc. The inductance of real-world iron core filter chokes depends to a certain extent on the direct current through the choke, which magnetically saturates the iron. One way to reduce this effect is to include an air gap in the iron core. The wider the gap, the less the inductance variation. But such a gap reduces the overall inductance. If a choke with constant inductance were used, it would need to have enough inductance for the lowest-current/highest load resistance condition, yet enough current capability for the highest current condition. That means a wide air gap. Such a choke would be large and expensive. Instead, a choke with a narrow air gap is used, Its inductance varies with the current - more inductance with less curren, less inductance with more current. This is exactly what is needed with a choke input filter. Such chokes are called "swinging chokes". The power supply for my 150 watt homebrew rig uses a swinging choke in the high voltage supply. This choke has 25 henries inductance at 30 mA DC but only 5 henries inductance at 300 mA DC. A 190V drop across it might be normal, or it might be a sign you are trying to pull way too much current through the thing. *What voltages do you measure across C162 sections A and B? *They should be fairly close to the maximum capacitor ratings, I suspect. *If they are within a reasonable range, I'd say the swinging choke is fine, otherwise I'd suspect something is on the secondary side is pulling too much current and it's hit the wall. All of the rectifiers, filter caps and resistors in the power supply section are suspect. This is particularly true if any selenium rectifiers or carbon composition resistors were used. 73 es GL de Jim, N2EY |
Hammarlund HX-50 choke question.
Chuck Harris wrote:
But that is exactly backwards from the way chokes work. As the current rises, and the core approaches saturation, the coil starts to lose the inductance enhancement provided by the core, and it approaches the inductance of an equivalent air core choke. That is, the inductance *drops*, and the inductive reactance *drops* and the AC current shoots way up. That makes perfect sense to me. So how _do_ current-limiting chokes work, then? I always assumed they worked as I described but I may well be wrong. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
Hammarlund HX-50 choke question.
Scott Dorsey wrote:
Chuck Harris wrote: But that is exactly backwards from the way chokes work. As the current rises, and the core approaches saturation, the coil starts to lose the inductance enhancement provided by the core, and it approaches the inductance of an equivalent air core choke. That is, the inductance *drops*, and the inductive reactance *drops* and the AC current shoots way up. That makes perfect sense to me. So how _do_ current-limiting chokes work, then? I always assumed they worked as I described but I may well be wrong. --scott On DC, they can't! No way, no how. On AC, a choke can limit the current by being a reactive component... kind of a lossless resistor for AC. But! Swinging chokes always reduce their inductance when the current rises. They typically have a 100:1 change in inductance over their design current range. -Chuck |
Hammarlund HX-50 choke question.
Chuck Harris wrote:
Scott Dorsey wrote: Chuck Harris wrote: But that is exactly backwards from the way chokes work. As the current rises, and the core approaches saturation, the coil starts to lose the inductance enhancement provided by the core, and it approaches the inductance of an equivalent air core choke. That is, the inductance *drops*, and the inductive reactance *drops* and the AC current shoots way up. That makes perfect sense to me. So how _do_ current-limiting chokes work, then? I always assumed they worked as I described but I may well be wrong. On DC, they can't! No way, no how. Right, but I was thinking that in the position where that coil is in the circuit, it's directly in series with the AC coming off the transformer. On AC, a choke can limit the current by being a reactive component... kind of a lossless resistor for AC. But! Swinging chokes always reduce their inductance when the current rises. They typically have a 100:1 change in inductance over their design current range. How does the reduced inductance translate to higher series impedance? --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
Hammarlund HX-50 choke question.
Scott Dorsey wrote:
Chuck Harris wrote: Scott Dorsey wrote: Chuck Harris wrote: But that is exactly backwards from the way chokes work. As the current rises, and the core approaches saturation, the coil starts to lose the inductance enhancement provided by the core, and it approaches the inductance of an equivalent air core choke. That is, the inductance *drops*, and the inductive reactance *drops* and the AC current shoots way up. That makes perfect sense to me. So how _do_ current-limiting chokes work, then? I always assumed they worked as I described but I may well be wrong. On DC, they can't! No way, no how. Right, but I was thinking that in the position where that coil is in the circuit, it's directly in series with the AC coming off the transformer. On AC, a choke can limit the current by being a reactive component... kind of a lossless resistor for AC. But! Swinging chokes always reduce their inductance when the current rises. They typically have a 100:1 change in inductance over their design current range. How does the reduced inductance translate to higher series impedance? It doesn't. Where did you get the idea that such an inductor exists? A swinging choke aids in the *voltage* regulation of a choke input power supply by having a high inductive reactance at low currents (where the supply would tend to be too high in voltage), and having low inductive reactance at high currents (where the supply would normally tend to droop.) Is that what you are thinking of? -Chuck |
Hammarlund HX-50 choke question.
Chuck Harris wrote:
A swinging choke aids in the *voltage* regulation of a choke input power supply by having a high inductive reactance at low currents (where the supply would tend to be too high in voltage), and having low inductive reactance at high currents (where the supply would normally tend to droop.) Is that what you are thinking of? Ahh! So the increased current causes the inductive reactance to drop, causing the series impedance to drop. That makes sense, so long as the source impedance is the same all the time, right? --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
Hammarlund HX-50 choke question.
Scott Dorsey wrote:
Chuck Harris wrote: A swinging choke aids in the *voltage* regulation of a choke input power supply by having a high inductive reactance at low currents (where the supply would tend to be too high in voltage), and having low inductive reactance at high currents (where the supply would normally tend to droop.) Is that what you are thinking of? Ahh! So the increased current causes the inductive reactance to drop, causing the series impedance to drop. That makes sense, so long as the source impedance is the same all the time, right? --scott If the source impedance changed, it could either help, or hurt the process. It would all depend on how it changed. But I would expect that for the usual diode, and transformer combination, the source impedance should be pretty stable. For a swinging choke to work, the power supply must be choke input. It is necessary that the choke see the massive AC ripple that comes out of the rectifier. No ripple, no regulating effect from the reactance. -Chuck |
Hammarlund HX-50 choke question.
Chuck Harris wrote:
For a swinging choke to work, the power supply must be choke input. It is necessary that the choke see the massive AC ripple that comes out of the rectifier. No ripple, no regulating effect from the reactance. Okay, wait a second. You're talking about a configuration where the choke is seeing both AC and DC on it, and both are required for regulation. The impressed AC is modulated by the DC, correct? As the DC voltage changes, the inductance changes, so the reactive part of the impedance changes and the AC voltage changes. Do I have that right? I was thinking about a configuration where the choke sees entirely AC, which would be a different thing altogether, like you see in arc lamp power supplies. I thought they worked the same way but it's clear they don't. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
Hammarlund HX-50 choke question.
Its Alive!!!
http://www.ppinyot.com/hammarlund.htm More work to be done but it now makes heat into a dummy load. Thanks for all the suggestions. Paul. |
Hammarlund HX-50 choke question.
"Paul P" wrote in message news:WbPDh.1220$JB2.1177@trnddc07... Its Alive!!! http://www.ppinyot.com/hammarlund.htm More work to be done but it now makes heat into a dummy load. Thanks for all the suggestions. Paul. Congratulations!!! Sometimes it takes quite a bit of digging to discover what's wrong. -- --- Richard Knoppow Los Angeles, CA, USA -- Posted via a free Usenet account from http://www.teranews.com |
FU Hammarlund Testing later this week on FreeWheeler's net.
If all goes well with the alignment, I should be on next week, with this
rig, testing on the FreeWheelers Net 10:30 pm central 3.916 LSB. That band's crystal is working good. Paul KB3LZP |
FU Hammarlund Testing later this week on FreeWheeler's net.
On Feb 24, 4:18 pm, "Paul P"
wrote: If all goes well with the alignment, I should be on next week, with this rig, testing on the FreeWheelers Net 10:30 pm central 3.916 LSB. That band's crystal is working good. Paul KB3LZP What, besides the other option does FU mean? |
FU Hammarlund Testing later this week on FreeWheeler's net.
On 25 Feb 2007 00:14:00 -0800, "Steven"
wrote: On Feb 24, 4:18 pm, "Paul P" wrote: If all goes well with the alignment, I should be on next week, with this rig, testing on the FreeWheelers Net 10:30 pm central 3.916 LSB. That band's crystal is working good. Paul KB3LZP What, besides the other option does FU mean? LOL. Probably "follow-up", or maybe "full-up" testing... Dale I have plenty of FU boatanchors :) |
FU Hammarlund Testing later this week on FreeWheeler's net.
On Feb 25, 3:15 am, Dale Carlson wrote:
On 25 Feb 2007 00:14:00 -0800, "Steven" wrote: On Feb 24, 4:18 pm, "Paul P" wrote: If all goes well with the alignment, I should be on next week, with this rig, testing on the FreeWheelers Net 10:30 pm central 3.916 LSB. That band's crystal is working good. Paul KB3LZP What, besides the other option does FU mean? LOL. Probably "follow-up", or maybe "full-up" testing... Dale I have plenty of FU boatanchors :) Not the -BAR kind I hope. |
FU Hammarlund Testing later this week on FreeWheeler's net.
Follow Up. Perhaps I should have spelled it out. :~)
PP "Steven" wrote in message ups.com... On Feb 24, 4:18 pm, "Paul P" wrote: If all goes well with the alignment, I should be on next week, with this rig, testing on the FreeWheelers Net 10:30 pm central 3.916 LSB. That band's crystal is working good. Paul KB3LZP What, besides the other option does FU mean? |
FU Hammarlund Testing later this week on FreeWheeler's net.
On Feb 25, 5:24 pm, "Paul P"
wrote: Follow Up. Perhaps I should have spelled it out. :~) PP Thank goodness I never have to find a phone book to call 911 LOL |
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