Yes, Edd, this is the one that I hooked up my filter capacitors backwards on.
I lost my shortwave about a week ago and today I had a resistor to frame short that fried my transformer. I'm in bad need of a replacement as I don't want to loose this radio after all this. I've heard it perform and it's a great one. I've put my heart and soul into it and I won't give up.
Anyone who can help me find a replacement would be very much appreciated....
Neal
Thought that you had installed protection on the transformer earlier, when you were relating to a “warm” transformer.
Did you ever get involved in the troubleshooting of the unit initially, such that you would have taken the RAW ac voltage that was going to the 6X5’s, and have written them down. No problem on figuring the two filament current requirements, but the loaded
AC voltage across each end of the HV secondary of the transformer would really be nice to know…as it stands, I’m thinking of a design center of ~ 325-0-325 VAC , across all of the secondary proper.
Then I could pull up my spreadsheet inventory data of “ole radio crap.com” t-formers and see what best fills the bill in a compatible and ECONOMY transformer replacement .
Seems like that units using a double bell transformer ..on top and bottom…with the unit setting quite up high above the chassis isn’t it ? .
73's de Edd
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Hi Edd,
I am a 'learn it the hard way' type of guy. As you may have realized allready. But I do learn.
All I remember about the voltage on the Speaker was that it was about 345 on one pin and 245 or so on another pin. But that was DC. You're talking about ac. No I don't have that.
I don't have a double bell transformer. It all sits on top.
I'm double fusing it now, one on the line and one on the center tap to ground.
I got with Radio Daze people yesterday and I have a transformer on the way. It's a 275-0-275 with 138 VA and 6.3vac@5a and 5.0vac at 4 amps, but I won't need the 5vac will I? One of the specs was 150ma but I'm not sure where that's used.
Thanks for the input...Neal
:Did you ever get involved in the troubleshooting of the unit initially, such that you would have taken the RAW ac voltage that was going to the 6X5’s, and have written them down. No problem on figuring the two filament current requirements, but the loaded
:AC voltage across each end of the HV secondary of the transformer would really be nice to know…as it stands, I’m thinking of a design center of ~ 325-0-325 VAC , across all of the secondary proper.
:Then I could pull up my spreadsheet inventory data of “ole radio crap.com” t-formers and see what best fills the bill in a compatible and ECONOMY transformer replacement .
:
:Seems like that units using a double bell transformer ..on top and bottom…with the unit setting quite up high above the chassis isn’t it ? .
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:73's de Edd
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Vell…I am tellink’ you vun thing…..that set is probably not going to quite be seeing those 345 and 245 VDC figures on the B+ and sub B+ line again with a 275-0-275 high voltage secondary being used.
Also there is somewhat of the additional safety aspect by the use of a separate individual 6.3 VAC winding for the feeding of the 6X5 sets of filaments.
But there is the alternative of using a 5U4 tube in place of your potentially troublesome 6X5’s and then use the isolated 5 VAC winding for feeding its filament supply.
The 150 ma spec must have been the max current available of the HV secondary winding.
73's de Edd
I won't have a separate 6.3vac supply will I?
What pin # is the filament on a 6x5?
What pin # is the filament on a 5U4?
And finally, you don't think I went high enough on the HV. The chart seemed to degenerate characteristics as the voltage went higher?
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:Vell…I am tellink’ you vun thing…..that set is probably not going to quite be seeing those 345 and 245 VDC figures on the B+ and sub B+ line again with a 275-0-275 high voltage secondary being used.
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: Also there is somewhat of the additional safety aspect by the use of a separate individual 6.3 VAC winding for the feeding of the 6X5 sets of filaments.
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:But there is the alternative of using a 5U4 tube in place of your potentially troublesome 6X5’s and then use the isolated 5 VAC winding for feeding its filament supply.
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:The 150 ma spec must have been the max current available of the HV secondary winding.
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:73's de Edd
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I won't have a separate 6.3vac supply will I?
What pin # is the filament on a 6x5?
What pin # is the filament on a 5U4?
And finally, you don't think I went high enough on the HV. The chart seemed to degenerate characteristics as the voltage went higher?
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:Vell…I am tellink’ you vun thing…..that set is probably not going to quite be seeing those 345 and 245 VDC figures on the B+ and sub B+ line again with a 275-0-275 high voltage secondary being used.
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: Also there is somewhat of the additional safety aspect by the use of a separate individual 6.3 VAC winding for the feeding of the 6X5 sets of filaments.
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:But there is the alternative of using a 5U4 tube in place of your potentially troublesome 6X5’s and then use the isolated 5 VAC winding for feeding its filament supply.
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:The 150 ma spec must have been the max current available of the HV secondary winding.
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:73's de Edd
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Make your decision on the H-V winding based on what the resistors drop from the center tap to the chassis. Whatever that drop is, add it to the 345 volts at the rectifier side of the field coil, and that will be the voltage you need for the H-V winding. 350 or 360 should be adequate. If you want, go with 360 and add resistance if voltages are too high. A 275 volt winding will make your radio work, but audio power will be somewhat inadequate.
T.
I know you gain voltage when you rectify AC. I built a power supply once out of 220VAC single phase and ended up with 300VDC. Won't that be the case here. I gained 80 Volts just by rectifying it.
:The P-T273BX or the P-T274AX from www.tubesandmore.com will give you voltages closer to what you want. You can find pin-outs for the 5Y3G and 5V4G on this web site in the TUbes section. If you want, you can instead use the 6X5G with the 6.3 volt winding provided on the transformers. Fuse the center tap of the H-V winding, as you are already doing. ....Or else you can purchase a 6.3 volt filament transformer from the above supplier, and mount it under the chassis. Use it to feed the 6X5G tubes. The chassis is large enough to fit an extra transformer.
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:Make your decision on the H-V winding based on what the resistors drop from the center tap to the chassis. Whatever that drop is, add it to the 345 volts at the rectifier side of the field coil, and that will be the voltage you need for the H-V winding. 350 or 360 should be adequate. If you want, go with 360 and add resistance if voltages are too high. A 275 volt winding will make your radio work, but audio power will be somewhat inadequate.
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:T.
With a tube type rectifier, which has a bit of resistance, much of that extra peak voltage gets lost when under load. In a typical radio you will see pretty much the same coming out of the rectifier as was measured as an RMS voltage going into the rectifier. Sometimes there are small gains. If you want 345 volts between your rectifier and chassis (remember that the chassis has resistors between it and the center tap, so you won't be seeing full B circuit potential....when all tubes are in place), you are best off going with a high voltage winding of at least 325 volts AC RMS (which is typically how it is measured). I cannot tell you exactly what your gains will be, if any. I feel that you should go higher--about 350 or 360 VAC RMS. I don't remember every detail of every radio I've ever worked on. However, with just about every AC/DC set I've worked on, the B voltages were rarely much more than 125 or 130 volts when under load, with a 121-124 volt AC RMS line, and the Philco 60 which I recently took voltage readings on for another gentleman on here has a 360 volt AC RMS high voltage winding, and I saw just about the same in DC volts at the rectifier cathode (to the center tap....since a Philco 60's chassis has resistance between it and the center tap).
T.
You've certainly clarified the voltage issue. Thank You...but I was in such a hurry to get a transformer on it's way...I have apparently made another mistake. I sent an email to Radio Daze giving them all the specifications of the burnt up transformer and model number, and chassis number....asking them for the proper replacement transformer. I called them on the phone and took their advice on the matter and immediately got one on the way. It's in the mail.
Now, I could have been thinking of the voltages on my Zenith 7S682. I had to buy a speaker on ebay and it came with a open output transformer and a 5 prong plug. I needed a 4 prong but I was able to successfuly conver it. And it took some doing to get the impedance matched up right on the new output transformer that I had to buy. But the reason I mention all this is I done alot of measuring speaker voltage on the different pins. And now as I tell this story to you I'm becoming more certain that the 345vdc that I said was on my speaker was actually on that 7S682 set.
So I must admit that I don't know for sure what the secondary voltage on the zenith 10S589 was. I would think that a 10 tube set wouldn't have less HV than a 7 tube set. What do you think? The schematic shows 340 on pins 2 and 8 of the 6x5g rectifier tubes. So that's what I need right? It seem's I've been misled by radio daze. I'm so anxious to get it, it will be hard sending it back. But I certainly want the same quality of reception as I had before I fried it.
You say that I have resistors in line with my center tap to ground. Would that be R20 and 40 ohms of my Candohm resistor? That's where the short was that fried it.
What about the amp rating on the 6.3vac line. The Radio Daze guy made quite an issue about that. I told him I thought that I needed a higher voltage transformer and he pointed out that the higher voltage transformers had a lower amperage rating on the 6.3vac line. I believe it dropped from 5 amps to 3 amps going up to a 300-0-300 transformer.
You've convinced me...thank you for all the time you have taken to communicate this information to me. You're telling me I need a 350-0-350 correct?
:In a circuit where rectifier resistance is at a minimum, and the load is comparatively small, you can 'gain' voltage by rectifying AC. What's really happening is that the AC voltage given by your meter is the RMS voltage. It's the equivilant to a DC voltage that would give the same resistive heating power (wattage). An AC RMS voltage is really .707 of the actual peak value. If you take the voltage and divide it by .707, you will get the peak voltage, which is often a bit higher.
:
:With a tube type rectifier, which has a bit of resistance, much of that extra peak voltage gets lost when under load. In a typical radio you will see pretty much the same coming out of the rectifier as was measured as an RMS voltage going into the rectifier. Sometimes there are small gains. If you want 345 volts between your rectifier and chassis (remember that the chassis has resistors between it and the center tap, so you won't be seeing full B circuit potential....when all tubes are in place), you are best off going with a high voltage winding of at least 325 volts AC RMS (which is typically how it is measured). I cannot tell you exactly what your gains will be, if any. I feel that you should go higher--about 350 or 360 VAC RMS. I don't remember every detail of every radio I've ever worked on. However, with just about every AC/DC set I've worked on, the B voltages were rarely much more than 125 or 130 volts when under load, with a 121-124 volt AC RMS line, and the Philco 60 which I recently took voltage readings on for another gentleman on here has a 360 volt AC RMS high voltage winding, and I saw just about the same in DC volts at the rectifier cathode (to the center tap....since a Philco 60's chassis has resistance between it and the center tap).
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:T.
:Hi Thomas,
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:You've certainly clarified the voltage issue. Thank You...but I was in such a hurry to get a transformer on it's way...I have apparently made another mistake. I sent an email to Radio Daze giving them all the specifications of the burnt up transformer and model number, and chassis number....asking them for the proper replacement transformer. I called them on the phone and took their advice on the matter and immediately got one on the way. It's in the mail.
:
:Now, I could have been thinking of the voltages on my Zenith 7S682. I had to buy a speaker on ebay and it came with a open output transformer and a 5 prong plug. I needed a 4 prong but I was able to successfuly conver it. And it took some doing to get the impedance matched up right on the new output transformer that I had to buy. But the reason I mention all this is I done alot of measuring speaker voltage on the different pins. And now as I tell this story to you I'm becoming more certain that the 345vdc that I said was on my speaker was actually on that 7S682 set.
:
:So I must admit that I don't know for sure what the secondary voltage on the zenith 10S589 was. I would think that a 10 tube set wouldn't have less HV than a 7 tube set. What do you think? The schematic shows 340 on pins 2 and 8 of the 6x5g rectifier tubes. So that's what I need right? It seem's I've been misled by radio daze. I'm so anxious to get it, it will be hard sending it back. But I certainly want the same quality of reception as I had before I fried it.
:
:You say that I have resistors in line with my center tap to ground. Would that be R20 and 40 ohms of my Candohm resistor? That's where the short was that fried it.
:
:What about the amp rating on the 6.3vac line. The Radio Daze guy made quite an issue about that. I told him I thought that I needed a higher voltage transformer and he pointed out that the higher voltage transformers had a lower amperage rating on the 6.3vac line. I believe it dropped from 5 amps to 3 amps going up to a 300-0-300 transformer.
:
:You've convinced me...thank you for all the time you have taken to communicate this information to me. You're telling me I need a 350-0-350 correct?
:
::In a circuit where rectifier resistance is at a minimum, and the load is comparatively small, you can 'gain' voltage by rectifying AC. What's really happening is that the AC voltage given by your meter is the RMS voltage. It's the equivilant to a DC voltage that would give the same resistive heating power (wattage). An AC RMS voltage is really .707 of the actual peak value. If you take the voltage and divide it by .707, you will get the peak voltage, which is often a bit higher.
::
::With a tube type rectifier, which has a bit of resistance, much of that extra peak voltage gets lost when under load. In a typical radio you will see pretty much the same coming out of the rectifier as was measured as an RMS voltage going into the rectifier. Sometimes there are small gains. If you want 345 volts between your rectifier and chassis (remember that the chassis has resistors between it and the center tap, so you won't be seeing full B circuit potential....when all tubes are in place), you are best off going with a high voltage winding of at least 325 volts AC RMS (which is typically how it is measured). I cannot tell you exactly what your gains will be, if any. I feel that you should go higher--about 350 or 360 VAC RMS. I don't remember every detail of every radio I've ever worked on. However, with just about every AC/DC set I've worked on, the B voltages were rarely much more than 125 or 130 volts when under load, with a 121-124 volt AC RMS line, and the Philco 60 which I recently took voltage readings on for another gentleman on here has a 360 volt AC RMS high voltage winding, and I saw just about the same in DC volts at the rectifier cathode (to the center tap....since a Philco 60's chassis has resistance between it and the center tap).
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::T.
:according to a Zenith shop manual I have, the transformer should have 280 volts ac center tap to plate; 340 dc on the cathode. hope this helps
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::Hi Thomas,
::
::You've certainly clarified the voltage issue. Thank You...but I was in such a hurry to get a transformer on it's way...I have apparently made another mistake. I sent an email to Radio Daze giving them all the specifications of the burnt up transformer and model number, and chassis number....asking them for the proper replacement transformer. I called them on the phone and took their advice on the matter and immediately got one on the way. It's in the mail.
::
::Now, I could have been thinking of the voltages on my Zenith 7S682. I had to buy a speaker on ebay and it came with a open output transformer and a 5 prong plug. I needed a 4 prong but I was able to successfuly conver it. And it took some doing to get the impedance matched up right on the new output transformer that I had to buy. But the reason I mention all this is I done alot of measuring speaker voltage on the different pins. And now as I tell this story to you I'm becoming more certain that the 345vdc that I said was on my speaker was actually on that 7S682 set.
::
::So I must admit that I don't know for sure what the secondary voltage on the zenith 10S589 was. I would think that a 10 tube set wouldn't have less HV than a 7 tube set. What do you think? The schematic shows 340 on pins 2 and 8 of the 6x5g rectifier tubes. So that's what I need right? It seem's I've been misled by radio daze. I'm so anxious to get it, it will be hard sending it back. But I certainly want the same quality of reception as I had before I fried it.
::
::You say that I have resistors in line with my center tap to ground. Would that be R20 and 40 ohms of my Candohm resistor? That's where the short was that fried it.
::
::What about the amp rating on the 6.3vac line. The Radio Daze guy made quite an issue about that. I told him I thought that I needed a higher voltage transformer and he pointed out that the higher voltage transformers had a lower amperage rating on the 6.3vac line. I believe it dropped from 5 amps to 3 amps going up to a 300-0-300 transformer.
::
::You've convinced me...thank you for all the time you have taken to communicate this information to me. You're telling me I need a 350-0-350 correct?
::
:::In a circuit where rectifier resistance is at a minimum, and the load is comparatively small, you can 'gain' voltage by rectifying AC. What's really happening is that the AC voltage given by your meter is the RMS voltage. It's the equivilant to a DC voltage that would give the same resistive heating power (wattage). An AC RMS voltage is really .707 of the actual peak value. If you take the voltage and divide it by .707, you will get the peak voltage, which is often a bit higher.
:::
:::With a tube type rectifier, which has a bit of resistance, much of that extra peak voltage gets lost when under load. In a typical radio you will see pretty much the same coming out of the rectifier as was measured as an RMS voltage going into the rectifier. Sometimes there are small gains. If you want 345 volts between your rectifier and chassis (remember that the chassis has resistors between it and the center tap, so you won't be seeing full B circuit potential....when all tubes are in place), you are best off going with a high voltage winding of at least 325 volts AC RMS (which is typically how it is measured). I cannot tell you exactly what your gains will be, if any. I feel that you should go higher--about 350 or 360 VAC RMS. I don't remember every detail of every radio I've ever worked on. However, with just about every AC/DC set I've worked on, the B voltages were rarely much more than 125 or 130 volts when under load, with a 121-124 volt AC RMS line, and the Philco 60 which I recently took voltage readings on for another gentleman on here has a 360 volt AC RMS high voltage winding, and I saw just about the same in DC volts at the rectifier cathode (to the center tap....since a Philco 60's chassis has resistance between it and the center tap).
:::
:::T.
T.
So you think I may have had the right one to begin with? I've emailed Radio Daze asking for an rma allready. So are you saying I may have been right about 'gaining' voltage when you rectify it?
Anyone else out there have an opinion on this? Should I go for the 350-0-350 or the 275-0-275? They're both in the mail.
Edd, Doug, Radiodoc?
I'll do as you suggested Thomas. I thank you for the idea. I hope I can make it look not used.
:Try the 275 volt one first. 275/.707=388, so you might just get the 340 volts you want. I kind of doubt it, but it's possible. See if you can carefully connect the wires without making them look used. Use a very small amount of solder.
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:T.
I'll use jumpers.
Thomas,
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:So you think I may have had the right one to begin with? I've emailed Radio Daze asking for an rma allready. So are you saying I may have been right about 'gaining' voltage when you rectify it?
:
:Anyone else out there have an opinion on this? Should I go for the 350-0-350 or the 275-0-275? They're both in the mail.
:Edd, Doug, Radiodoc?
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:I'll do as you suggested Thomas. I thank you for the idea. I hope I can make it look not used.
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::Try the 275 volt one first. 275/.707=388, so you might just get the 340 volts you want. I kind of doubt it, but it's possible. See if you can carefully connect the wires without making them look used. Use a very small amount of solder.
::
::T.
T.
The transformer came in today (275-0-275) and I'm making up jumpers to try it now. At least we'll know one way or another. I appreciate all this help.
:I don't see the filter capacitors holding 340 volts under load, since 388 is only a peak value. I have quite a few radios.......perhaps not as many as others on here, but enough to see a basic pattern. The pattern I've seen is that the rectified B voltage usually isn't much more than the AC RMS voltage. On occasion it is. There is no way that the first electrolytic can maintain a steady peak voltage, since the peak occurs for such a short time. It may hold a lower voltage with the peak ripple on it, which then gets filtered by the field coil and second electrolytic. Voltage drop through the rectifier and the load of the radio further drop the voltage. I have no way of knowing for sure, though, how your set will behave.
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:T.
which transformer wires go to pins 2, 7-8 on the 6fxg. The pin voltage on the schematic says 340vdc. I've been thinking that those are tube output pins, but in hooking this up I see that there are transformer wires hooked there. I have my 275 hooked to pins 3,5 as is called for on the schematic. All I have left is my 6.3 w/ct windings and my 5 volt windings?
Thomas,
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:The transformer came in today (275-0-275) and I'm making up jumpers to try it now. At least we'll know one way or another. I appreciate all this help.
:
::I don't see the filter capacitors holding 340 volts under load, since 388 is only a peak value. I have quite a few radios.......perhaps not as many as others on here, but enough to see a basic pattern. The pattern I've seen is that the rectified B voltage usually isn't much more than the AC RMS voltage. On occasion it is. There is no way that the first electrolytic can maintain a steady peak voltage, since the peak occurs for such a short time. It may hold a lower voltage with the peak ripple on it, which then gets filtered by the field coil and second electrolytic. Voltage drop through the rectifier and the load of the radio further drop the voltage. I have no way of knowing for sure, though, how your set will behave.
::
::T.
If you prefer not to have the 6X5s powered from the same 6.3 volt winding as the rest of the tubes, obtain a 12.6 volt transformer from Radio Shack. Connect the center tap to pin 2 of each 6X5. Connect one end of the 12.6 volt winding to pin 7 of one 6X5, and connect the other end of the 12.6 volt winding to pin 7 of the other 6X5. Do not connect the filament wiring to the chassis in any way. The transformer can be neatly concealed under the chassis, and will prevent catastrophy, should either of the 6X5s develop a heater to cathode short.
T.
T.
I looked at the HV while I had it powered up and it read 313vac on both HV wires.
:I am assuming that you are using the 6X5 rectifier. The ends of the high voltage winding go to pins 3 and 5. 2 and 7 go to the 6.3 volt filament winding that powers the rest of the radio. The 5.0 volt winding is not used. If you prefer, put 5Y3 tubes in the 6x5 sockets, and use the 5.0 volt winding to power the 5y3s. It will probably only be able to power one 5y3, so it is best to use one. Actually the schematic shows each of the 6x5 tubes having its plates in parallel, so connect 3 and 5 of one tube to one end of the high voltage winding, and 3 and 5 of the other tube to the other end of the high voltage winding. Connect the center tap to B- as indicated in the schematic. Since you will be using the main 6.3 volt winding to power the 6X5 tubes, it is best to put a #47 lamp or a 1 ampere fuse in series with the power transformer center tap so that a heater to cathode short in one of the 6X5s doesn't destroy the transformer. Pin 8 of both 6X5s should be connected to the beginning of the B+ circuit, as indicated in the schematic.
:
:If you prefer not to have the 6X5s powered from the same 6.3 volt winding as the rest of the tubes, obtain a 12.6 volt transformer from Radio Shack. Connect the center tap to pin 2 of each 6X5. Connect one end of the 12.6 volt winding to pin 7 of one 6X5, and connect the other end of the 12.6 volt winding to pin 7 of the other 6X5. Do not connect the filament wiring to the chassis in any way. The transformer can be neatly concealed under the chassis, and will prevent catastrophy, should either of the 6X5s develop a heater to cathode short.
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:T.
With 315 volts, sounds like 275 and 350 might be too low and too high. 315 volts should give you decent set operation, so you can stick with that transformer if you wish. Otherwise purchase a 300 or a 325 volt transformer. That will probably put you more where you need to be. Sorry for the trial and error. It's easier when set voltages are given in the schematic. For each radio the resulting B voltage is a bit different. It depends on electrolytic size and current draw and other things. Like I said, your peak voltage will be much higher than the AC RMS voltage, but the peak is so short in occurrance that it doesn't do too much. In some radios with low current draw, the electrolytics can be charged up quite a bit--near peak value. In others, however, the electrolytics won't charge up anywhere near peak value. In your case 275 volts AC RMS calculates to 388 volts peak.....and 315 is nowhere near 388.
T.
Thomas,
:which transformer wires go to pins 2, 7-8 on the 6fxg. The pin voltage on the schematic says 340vdc. I've been thinking that those are tube output pins, but in hooking this up I see that there are transformer wires hooked there. I have my 275 hooked to pins 3,5 as is called for on the schematic. All I have left is my 6.3 w/ct windings and my 5 volt windings?
:
:Thomas,
::
::The transformer came in today (275-0-275) and I'm making up jumpers to try it now. At least we'll know one way or another. I appreciate all this help.
::
:::I don't see the filter capacitors holding 340 volts under load, since 388 is only a peak value. I have quite a few radios.......perhaps not as many as others on here, but enough to see a basic pattern. The pattern I've seen is that the rectified B voltage usually isn't much more than the AC RMS voltage. On occasion it is. There is no way that the first electrolytic can maintain a steady peak voltage, since the peak occurs for such a short time. It may hold a lower voltage with the peak ripple on it, which then gets filtered by the field coil and second electrolytic. Voltage drop through the rectifier and the load of the radio further drop the voltage. I have no way of knowing for sure, though, how your set will behave.
:::
:::T.
thomas,
::which transformer wires go to pins 2, 7-8 on the 6fxg. The pin voltage on the schematic says 340vdc. I've been thinking that those are tube output pins, but in hooking this up I see that there are transformer wires hooked there. I have my 275 hooked to pins 3,5 as is called for on the schematic. All I have left is my 6.3 w/ct windings and my 5 volt windings?
::
::Thomas,
:::
:::The transformer came in today (275-0-275) and I'm making up jumpers to try it now. At least we'll know one way or another. I appreciate all this help.
:::
::::I don't see the filter capacitors holding 340 volts under load, since 388 is only a peak value. I have quite a few radios.......perhaps not as many as others on here, but enough to see a basic pattern. The pattern I've seen is that the rectified B voltage usually isn't much more than the AC RMS voltage. On occasion it is. There is no way that the first electrolytic can maintain a steady peak voltage, since the peak occurs for such a short time. It may hold a lower voltage with the peak ripple on it, which then gets filtered by the field coil and second electrolytic. Voltage drop through the rectifier and the load of the radio further drop the voltage. I have no way of knowing for sure, though, how your set will behave.
::::
::::T.
I have not read the progress lately, but looks like you have deux tranfo in hand and are about to try the initial one that you jumped at, I repeat again what I said in the respect of that initially supplied transformer not being to spec in the respect of the lack of a second 6.3 dedicated winding for the 6X5’s.... if you are still considering utilizing that tube type.
As the set is wired, reviewing my thumbnail, if you try using a single 6.3 VAC winding to power both the sets filament supply AND the rectifiers, they are directly shorted to ground via the cathode to filament connection…as you can see by my red markup of the primary B+ bus in red and the red ground circle around the sets standard filament winding to the left filament yellow mark up box.
If you happen to lift the 6X5 cathodes connections and thus isolate them from their filaments, that will have an isolated B+ derivation present at the cathodes, up to that future point in time until filament oxide coating shifts / cracks / depletes to the point where exposure initiates the eventual fireworks display occurrence between the 6X5 Filament-Cathode spacing.
Should you now want to merely evaluate the transformers high voltage loading factor / pull down characteristics, you could sub in a 5Y3 or 5-useless-4 and use the isolated 5VAC winding to supply its filamental supply and then that should permit powering up to then check the sets B+ voltage branches under set loading conditions.
Me still thinks that the median would be the initially mentioned sec voltage I had given, right at the ~ 325 VAC, with a 350 VAC figure being right on up at the high end border.
This set uses the design utilization of the employment of a stacked secondary negative bias supply, it being derived from the HV center tap thru the wire wound resistors R---20 and the 40 ohms of R---19 .(Marked up green path) Therefore, that will offset the overall max available raw B+ in the order of ~15-22VC.
Lastly, write down your voltages and keep track of them this time...they are invaluable in future troubleshooting as well as in assisting others with this is chassis series.
Reference Thumbnail + Tube specs:
73's de Edd
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:I have not read the progress lately, but looks like you have deux tranfo in hand and are about to try the initial one that you jumped at, I repeat again what I said in the respect of that initially supplied transformer not being to spec in the respect of the lack of a second 6.3 dedicated winding for the 6X5’s.... if you are still considering utilizing that tube type.
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:As the set is wired, reviewing my thumbnail, if you try using a single 6.3 VAC winding to power both the sets filament supply AND the rectifiers, they are directly shorted to ground via the cathode to filament connection…as you can see by my red markup of the primary B+ bus in red and the red ground circle around the sets standard filament winding to the left filament yellow mark up box.
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:If you happen to lift the 6X5 cathodes connections and thus isolate them from their filaments, that will have an isolated B+ derivation present at the cathodes, up to that future point in time until filament oxide coating shifts / cracks / depletes to the point where exposure initiates the eventual fireworks display occurrence between the 6X5 Filament-Cathode spacing.
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:Should you now want to merely evaluate the transformers high voltage loading factor / pull down characteristics, you could sub in a 5Y3 or 5-useless-4 and use the isolated 5VAC winding to supply its filamental supply and then that should permit powering up to then check the sets B+ voltage branches under set loading conditions.
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:Me still thinks that the median would be the initially mentioned sec voltage I had given, right at the ~ 325 VAC, with a 350 VAC figure being right on up at the high end border.
:This set uses the design utilization of the employment of a stacked secondary negative bias supply, it being derived from the HV center tap thru the wire wound resistors R---20 and the 40 ohms of R---19 .(Marked up green path) Therefore, that will offset the overall max available raw B+ in the order of ~15-22VC.
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:Lastly, write down your voltages and keep track of them this time...they are invaluable in future troubleshooting as well as in assisting others with this is chassis series.
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:Reference Thumbnail + Tube specs:
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:73's de Edd
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If you decide to use a separate 6.3 volt transformer for the 6X5s, the filaments can remain connected to the cathodes.
....So did you try out your new transformer yet? How are the voltages? I am curious to know. They might be just fine, but I am guessing that they will be low.
T.
I checked my voltages right out of the box. They were all high. I had 313 where I should have had 275. 7.1 where I should have had 6.3 And a 5.0 that was a little high also. When I hooked it up I had 410vdc on my speaker pins. But most of my tubes weren't even hot. I'm going to try to use the 5.0 as my secondary 6.3 circuit. The old transformer lead connected there and went from tube to tube on pin 2 and on to my pilot lights. I have trouble with my candohm resistor, so I'll probably have to replace that before anymore voltage checks. Is 410vdc too high? Maybe that will change when I get my candohm replaced. But the 313vac out of the box, before hookup quite surprised me.
On the schematic it looks like my pilot lights are 110vac but they're not. They're 6.3 and they come on when you connect the negative to chassis ground...thanks for your help in all this.
:Notice what Edd shows about the 6X5 filament wiring originally being connected to the cathodes. If you use the 6.3 volt winding in your new transformer that also powers the rest of the tubes, be absolutely sure that the 6X5 cathodes are no longer connected to the filaments (pin 8 should not be connected to pins 2 or 7). Be sure to fuse the center tap of the high voltage winding of the transformer so that any heater to cathode shorts in the 6X5s won't destroy your new transformer.
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:If you decide to use a separate 6.3 volt transformer for the 6X5s, the filaments can remain connected to the cathodes.
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:....So did you try out your new transformer yet? How are the voltages? I am curious to know. They might be just fine, but I am guessing that they will be low.
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:T.
T.
Now comes the good part. I got bit by a NEGATIVE 400vdc on the E trimmer. That was after the candohm went open. When it bites you, measure it, right? LOL
Anyway, I'm going to jump into ordering some heat sinked resistors from mouser.com. and until they get here, all is on hold. Thanks for your help.
:I wonder where you are getting 410 volts from 275.
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:T.
How many watts do the replacement resistors (for the candohm) have to be? Where Watts=voltsXamps, I hope the current is way low in the milliamps or I'm going to need lotsa watts.
:It came out of the box reading 313 where it should have been 275. Still that's alot of voltage. My candohm resistor opened up in the 40 ohm section. With a lesser current flow the voltage goes up. Maybe that was it. Anyway, when my candohm opened up, I lost all voltage on my speaker pins. My transformer is still ok, with the center tap fused and all.
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:Now comes the good part. I got bit by a NEGATIVE 400vdc on the E trimmer. That was after the candohm went open. When it bites you, measure it, right? LOL
:
:Anyway, I'm going to 'jump' into ordering some heat sinked resistors from mouser.com. and until they get here, all is on hold. Thanks for your help.
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::I wonder where you are getting 410 volts from 275.
::
::T.
Be sure you don't mistake one of the highvoltage plate leads for the centertap. This mistake can cause the B+ voltage to be high. A resistance measurement of the highvoltage winding will determine the centertap lead.
Radiodoc
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:It came out of the box reading 313 where it should have been 275. Still that's alot of voltage. My candohm resistor opened up in the 40 ohm section. With a lesser current flow the voltage goes up. Maybe that was it. Anyway, when my candohm opened up, I lost all voltage on my speaker pins. My transformer is still ok, with the center tap fused and all.
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:Now comes the good part. I got bit by a NEGATIVE 400vdc on the E trimmer. That was after the candohm went open. When it bites you, measure it, right? LOL
:
:Anyway, I'm going to jump into ordering some heat sinked resistors from mouser.com. and until they get here, all is on hold. Thanks for your help.
:
::I wonder where you are getting 410 volts from 275.
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::T.
My HV leads are red and the ct is red/yellow, but that's good advice and I'm certainly capable of such a mistake. Hooking up my filter capacitors backwards is what got me into this mess.
Thomas,
I have found replacements for the candohm resistor and have a power up. I went 20 Watts which seems to be enough. I've passed the smoke test. I have those voltages for you. I have 326VDC on 6x5's 2, 7, and 8. I have 265 on the Sub B (I think that's what you call it) line. Anyway it's on the lower voltage speaker pin.
I used my 5vac windings for the second 6.3 source. I had 5.3vac where I should have had 6.1. I think I'll use a 2nd transformer for that. The way it was hooked up, the original transformer had to have two separate 6.3 windings.
I'm definitely not satisfied with the audio output. Thank you for suggesting this proceedure. I'm going to return this one to radio daze and use the 350-0-350 that's yet in the mail.
Well, it's been a long night, midnight shift and all. But we're slowly mucking our way out of the mud pit I fell into...Neal
Neal,
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:Be sure you don't mistake one of the highvoltage plate leads for the centertap. This mistake can cause the B+ voltage to be high. A resistance measurement of the highvoltage winding will determine the centertap lead.
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:Radiodoc
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::It came out of the box reading 313 where it should have been 275. Still that's alot of voltage. My candohm resistor opened up in the 40 ohm section. With a lesser current flow the voltage goes up. Maybe that was it. Anyway, when my candohm opened up, I lost all voltage on my speaker pins. My transformer is still ok, with the center tap fused and all.
::
::Now comes the good part. I got bit by a NEGATIVE 400vdc on the E trimmer. That was after the candohm went open. When it bites you, measure it, right? LOL
::
::Anyway, I'm going to jump into ordering some heat sinked resistors from mouser.com. and until they get here, all is on hold. Thanks for your help.
::
:::I wonder where you are getting 410 volts from 275.
:::
:::T.
Regarding your voltages, are you using a digital meter or an electro-mechanical (anolog) meter? I think that most digital meters are designed to read AC RMS voltage, though not necessarily. A mechanical meter is slower, though, and is less likely to measure the peaks of the voltage, so you might get slightly lower readings with a mechanical meter. Also be sure to test your line voltage, though a small increase in line voltage shouldn't change 275 all the way to 315. If all is working well, and the voltages are a bit high with this transformer, then perhaps you can continue to use it. Just add resistance to the B circuit to reduce the voltage appropriately. Be sure to add resistance to the + side of the B circuit (off of pin 8 of the rectifiers) so that you don't affect biasing in the negative side of the circuit.
T.
My candohm resistor was damaged (failed smoke test) about a month ago when I was replacing my electrolytics. I picked a wrong wire and got them backwards. It still worked after that, but it was damaged. Then it totally failed during that voltage test. Sounds like I have them sufficiently replaced. I have two 100 ohm 10 Watt in series for the 200ohm section and a 40 clarostat 25 Watt for the other. They didn't even get very warm this morning.
I'm using a 117 Fluke digital meter true RMS.
My Audio was inadequate, so I've sent the 275-0-275 back to Radio Daze and I am awaiting the 350-0-350 coming from Antique Electronic Supply. It should be here shortly.
Thanks for helping me learn how to hook this up. Did I tell you that I have decided to use a 120/12.6 ct transformer for the secondary 6.3vac supply.
Well, time to go to work...talk to ya later....Neal
:I think that your h-v leads are wired correctly. For the Candohm resistor, 10 watt resistors should be adequate, and heat sinking them will probably be unnecessary, though not definitely. Make sure that nothing is wrong with your radio. Candohm resistors don't usually just open up unless they're corroded or overworked. They do on occasion open up for no reason, so it is possible that your resistor just decided to go South on its own, but make sure that was the reason.
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:Regarding your voltages, are you using a digital meter or an electro-mechanical (anolog) meter? I think that most digital meters are designed to read AC RMS voltage, though not necessarily. A mechanical meter is slower, though, and is less likely to measure the peaks of the voltage, so you might get slightly lower readings with a mechanical meter. Also be sure to test your line voltage, though a small increase in line voltage shouldn't change 275 all the way to 315. If all is working well, and the voltages are a bit high with this transformer, then perhaps you can continue to use it. Just add resistance to the B circuit to reduce the voltage appropriately. Be sure to add resistance to the + side of the B circuit (off of pin 8 of the rectifiers) so that you don't affect biasing in the negative side of the circuit.
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:T.
Good idea with the second 6.3 volt transformer. Radio Shack has some fairly good ones (12.6V w/ center tap) with good primary to secondary isolation, and both www.tubesandmore.com and www.radiodaze.com have good 6.3 volt filament transformers.
T.
Here's a quote from one of your earlier posts:
Make your decision on the H-V winding based on what the resistors drop from the center tap to the chassis. Whatever that drop is, add it to the 345 volts at the rectifier side of the field coil, and that will be the voltage you need for the H-V winding. 350 or 360 should be adequate. If you want, go with 360 and add resistance if voltages are too high. A 275 volt winding will make your radio work, but audio power will be somewhat inadequate.
T.
Well I didn't do the calculations suggested, but I went with the 350 and it is adequate. 418 adequate. Where do the resistors go, in series with the HV winding and pin 3 and 5 on each tube? Or needn't I worry.
Also, does it make any difference which 6.3 circuitry I use the second transformer on. You described how to use it to drive the 6x5's. Would it matter if I used it to drive the rest of the tubes instead? I was going to use it to drive the rest of the tubes, but in reviewing our correspondence you specifically recommended the second 6.3 source to drive the 6X5's.
The set sounds good. I brought it up slowly and it didn't seem to mind the extra 80vdc.
nom
:What were your voltages once the radio was working properly? Don't replace the transformer unless the voltages are actually too low. If they are where they should be, then you shouldn't increase them. I am assuming that with the radio loading the power supply, the voltages did go down, but perhaps not?
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:Good idea with the second 6.3 volt transformer. Radio Shack has some fairly good ones (12.6V w/ center tap) with good primary to secondary isolation, and both www.tubesandmore.com and www.radiodaze.com have good 6.3 volt filament transformers.
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:T.
:My candohm resistor was damaged (failed smoke test) about a month ago when I was replacing my electrolytics. I picked a wrong wire and got them backwards. It still worked after that, but it was damaged. Then it totally failed during that voltage test.
Assumedly to replace your dee-funked….and HEAVY on the FUNKED…Candohm unit, and can I assume that you are ordered some of the Dale power..alum-i-ninny-yum-yum cased power resistors …or some of the like knock offs being second sourced by other manufacturers..... in order to then build up another discrete unit ?
In my case, I will take the prescribed number of them needing to be used in replacing the units of a Candohm / Muter power strip resistor and then mount them in the required spaced out linear layout and then mechanically , tap mount them onto a ¼ in thick by 1 inch wide by XXX? required length of aluminum bar stock, using 2x per, flat head Phillips screws coming up from the bottom of the bar stock. That then leaves a flat aluminum bar side to clamp mount onto the chassis for its optimal heat sinking.
If encountering any odd values of power resistors I will shoot for the closest value power resistor just above the needed value and then trim down to exact spec by shunting across the power resistor with a mechanically small 2-3-5 watt metal film resistor.
That leaves the bulk of the power being automatically proportionately distributed across the pair, but with only a wee bit going to the add on shunting resistor.
Pictorial visual:
Clean profile…hummmmm ?
73's de Edd
The question now is have I gone to high on the power transformer? I've got a 350-0-350 in and up and running. I have PLENNNNNNNTY of volume now, but have I superceeded the radio's capabilities? After slowly running up the voltage on my variac, I have arrived at line voltage and I have 418vdc and 334vdc on my speaker pins.
Do you think this set can handle that much. Seems to be working fine right now, but still no SW.
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::My candohm resistor was damaged (failed smoke test) about a month ago when I was replacing my electrolytics. I picked a wrong wire and got them backwards. It still worked after that, but it was damaged. Then it totally failed during that voltage test.
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:Assumedly to replace your dee-funked….and HEAVY on the FUNKED…Candohm unit, and can I assume that you are ordered some of the Dale power..alum-i-ninny-yum-yum cased power resistors …or some of the like knock offs being second sourced by other manufacturers..... in order to then build up another discrete unit ?
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:In my case, I will take the prescribed number of them needing to be used in replacing the units of a Candohm / Muter power strip resistor and then mount them in the required spaced out linear layout and then mechanically , tap mount them onto a ¼ in thick by 1 inch wide by XXX? required length of aluminum bar stock, using 2x per, flat head Phillips screws coming up from the bottom of the bar stock. That then leaves a flat aluminum bar side to clamp mount onto the chassis for its optimal heat sinking.
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:If encountering any odd values of power resistors I will shoot for the closest value power resistor just above the needed value and then trim down to exact spec by shunting across the power resistor with a mechanically small 2-3-5 watt metal film resistor.
:That leaves the bulk of the power being automatically proportionately distributed across the pair, but with only a wee bit going to the add on shunting resistor.
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:Pictorial visual:
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:Clean profile…hummmmm ?
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:73's de Edd
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Well, whoever you are, what I get out of that is it might be okay...but I'm pushing it.
:http://frank.yueksel.org/sheets/127/6/6X5.pdf
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:Well, whoever you are, what I get out of that is it might be okay...but I'm pushing it.
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::http://frank.yueksel.org/sheets/127/6/6X5.pdf
Hi Neal,
The data sheet says that the 6X5 is good up to 450 volts. This is typically the weak spot, too.
As a kid I replaced the power transformer in my parent's TV with one that was too high a voltage. The problem showed up as periodic arcing. I won't do that again.
Best Regards,
Bill Grimm
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::Well, whoever you are, what I get out of that is it might be okay...but I'm pushing it.
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:::http://frank.yueksel.org/sheets/127/6/6X5.pdf
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Hi Bill,
I've got it turned down in the variac to 340 volts right now. I noticed it surge up to 500vdc on power up when I was using regular line voltage. My two filter capacitors are only rated for 450vdc. Thanks for your input.
Hi Neal,
: The data sheet says that the 6X5 is good up to 450 volts. This is typically the weak spot, too.
: As a kid I replaced the power transformer in my parent's TV with one that was too high a voltage. The problem showed up as periodic arcing. I won't do that again.
:
:Best Regards,
:
:Bill Grimm
Sorry for the hit-and-miss approach. Without original voltage data, however, you need a LOT of math in order to accurately calculate exactly what transformer you need. You need to know how much of the peak voltage the electrolytics will retain under load, etc. The data sheets tell what the voltage drop is across the tube at a certain current draw (I believe that it is 70 mA). Using that data, you can tell what the tube will drop for other current draws, and since you have two tubes, you can divide the current across the two..........though your schematic doesn't mention current draw, either. You can approximate current draw by looking at data for the other tubes.
If you prefer to have the proper transformer, and not to have the set over or under powered, you can take a variac and adjust until you get voltages you like. Take AC readings at the transformer, then, which will tell you what size transformer you need. Keep in mind, though, that when you use a variac on the set, the tubes will dim, unless you feed their filaments from another source. A 350 volt transformer and variac would be a nice thing to have at your bench for future work where it is unknown what voltages were present at a burned out transformer. Simply hook to the radio in question and adjust the variac until voltages are agreeable. .....But you might not necessarily want an expensive 350 volt transformer just lying around......or you might? It isn't too bad of an idea if you do a lot of radio work.
T.
:I think that you would be better off with a 325 or 315 volt transformer.....for safety, but as the data sheet says, the 6X5 can handle up to 450 volts. The data sheet says to stay at or below 325 volts (at cathode--DC volts) for capacitive filter input, because if the set is turned off and on right away with the tubes warm, the input electrolytic will overload the 6X5, causing arc-over. I have seen Zeniths arc over before, though. It isn't that uncommon. I think that 500 volts with no load is a bit excessive for the electrolytics, though they usually have a safety threshold, and can handle that for a brief moment. I'd prefer to avoid the threshold, myself.
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:Sorry for the hit-and-miss approach. Without original voltage data, however, you need a LOT of math in order to accurately calculate exactly what transformer you need. You need to know how much of the peak voltage the electrolytics will retain under load, etc. The data sheets tell what the voltage drop is across the tube at a certain current draw (I believe that it is 70 mA). Using that data, you can tell what the tube will drop for other current draws, and since you have two tubes, you can divide the current across the two..........though your schematic doesn't mention current draw, either. You can approximate current draw by looking at data for the other tubes.
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:If you prefer to have the proper transformer, and not to have the set over or under powered, you can take a variac and adjust until you get voltages you like. Take AC readings at the transformer, then, which will tell you what size transformer you need. Keep in mind, though, that when you use a variac on the set, the tubes will dim, unless you feed their filaments from another source. A 350 volt transformer and variac would be a nice thing to have at your bench for future work where it is unknown what voltages were present at a burned out transformer. Simply hook to the radio in question and adjust the variac until voltages are agreeable. .....But you might not necessarily want an expensive 350 volt transformer just lying around......or you might? It isn't too bad of an idea if you do a lot of radio work.
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:T.
You once mentioned I could add resistance to bring my voltages down. Can you describe that for me?
:I was trying to check my voltages with the variac down to where I could see the proper secondary winding, in order to get the right transformer this time, when a 6x5 tube failed. It was the 2nd one that was damaged in my electrolytic screwup. I've asked Edd about changing rectifier tubes at this time also. I will need the radio up and running to check the voltages so it's tube time first. 3rd time is the charm, I hope. Thanks for you input.
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::I think that you would be better off with a 325 or 315 volt transformer.....for safety, but as the data sheet says, the 6X5 can handle up to 450 volts. The data sheet says to stay at or below 325 volts (at cathode--DC volts) for capacitive filter input, because if the set is turned off and on right away with the tubes warm, the input electrolytic will overload the 6X5, causing arc-over. I have seen Zeniths arc over before, though. It isn't that uncommon. I think that 500 volts with no load is a bit excessive for the electrolytics, though they usually have a safety threshold, and can handle that for a brief moment. I'd prefer to avoid the threshold, myself.
::
::Sorry for the hit-and-miss approach. Without original voltage data, however, you need a LOT of math in order to accurately calculate exactly what transformer you need. You need to know how much of the peak voltage the electrolytics will retain under load, etc. The data sheets tell what the voltage drop is across the tube at a certain current draw (I believe that it is 70 mA). Using that data, you can tell what the tube will drop for other current draws, and since you have two tubes, you can divide the current across the two..........though your schematic doesn't mention current draw, either. You can approximate current draw by looking at data for the other tubes.
::
::If you prefer to have the proper transformer, and not to have the set over or under powered, you can take a variac and adjust until you get voltages you like. Take AC readings at the transformer, then, which will tell you what size transformer you need. Keep in mind, though, that when you use a variac on the set, the tubes will dim, unless you feed their filaments from another source. A 350 volt transformer and variac would be a nice thing to have at your bench for future work where it is unknown what voltages were present at a burned out transformer. Simply hook to the radio in question and adjust the variac until voltages are agreeable. .....But you might not necessarily want an expensive 350 volt transformer just lying around......or you might? It isn't too bad of an idea if you do a lot of radio work.
::
::T.
In this post you are suggesting that I use a 5U4 tube in place of this troublesome 6x5. Does it cross directly, or would I need to isolate my pin 8. I have a transformer that is too high now 350.
The second tube that was damaged in my electrolytic screw up failed today. It failed when I had the variac down to where I have proper voltages on speaker pins. I was trying to measure what ac output would give me the desired voltage on my speaker pins (340) and the tube started making a humm, then 'poof', I blew a line fuse and the tube.
So I'm going to buy new rectifier tubes and another transformer, and now would be the time to change to 5U4's like you suggested. What do you think? Are they more durable?
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:Vell…I am tellink’ you vun thing…..that set is probably not going to quite be seeing those 345 and 245 VDC figures on the B+ and sub B+ line again with a 275-0-275 high voltage secondary being used.
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: Also there is somewhat of the additional safety aspect by the use of a separate individual 6.3 VAC winding for the feeding of the 6X5 sets of filaments.
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:But there is the alternative of using a 5U4 tube in place of your potentially troublesome 6X5’s and then use the isolated 5 VAC winding for feeding its filament supply.
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:The 150 ma spec must have been the max current available of the HV secondary winding.
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:73's de Edd
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