I think you have just been lucky with that specific 10M45 CCS. It is working way over it's rating.
R14 was just pulled by one leg and tested and read 10.001K, it is also labelled as 10KOhm 3W and 5%, a pale blue casing.
Just as a bit of history of the amp, it worked first time and well, the right channel was damaged because of a mechanical mistake which caused an unfortunate output short to input.
Now, it appears my solder pump has escaped from the work area and is nowhere to be seen...
Just as a bit of history of the amp, it worked first time and well, the right channel was damaged because of a mechanical mistake which caused an unfortunate output short to input.
Now, it appears my solder pump has escaped from the work area and is nowhere to be seen...
Looks like I'd better get the readings done again properly as it would be odd for sure. This said, I think I remember someone saying they're rather robust, which surprised me as well.
It might totally be damaged, and that would be the second one. I have the previous one (probably also damaged in that case) and no spare ones for now.
You should try and get some true readings of the Voltages on the 9 pins so maybe I or other more knowledgeable members will be able to help. Get the readings on the pins of the outputs tubes as well, both of them so we can compare. It is a simple solution to fix, we just need to figure out what it is.
I tend to agree.
The only way to have the entire B+ on the 12AT7 plate is for the 10M45 to short.
Which is certainly possible, but I would expect to also see some visual artifacts - like red plate on the 12AT7, maybe a smoking cathode resistor. Can't say for certain - haven't put 450 on a 12AT7, but those kind of voltages will sure light up a 5842 ....
Win W5JAG
OK, help people to help you without having to read seventeen pages ....
1) The right output is dead?
2) You cross connected the coupling caps at the output side, determined that when the right side output received drive from the left channel, it was working, and so the problem was confined to the right side input?
3) You have since made changes to the right side output, so it is now possible that in addition to the right side input not working, it is also possible that the right side output no longer works?
4) If 3) is true, maybe you should repeat 2) to know where you stand - input, output, or both not working.
If right side output works, check your wiring from the input jacks to the board really carefully. If the right side worked once, and these connections were altered, that's probably your trouble.
Do you have anything besides a DMM? Can it read audio level ac voltages so you can try to trace the audio signal?
Win W5JAG
1) The right output is dead?
2) You cross connected the coupling caps at the output side, determined that when the right side output received drive from the left channel, it was working, and so the problem was confined to the right side input?
3) You have since made changes to the right side output, so it is now possible that in addition to the right side input not working, it is also possible that the right side output no longer works?
4) If 3) is true, maybe you should repeat 2) to know where you stand - input, output, or both not working.
If right side output works, check your wiring from the input jacks to the board really carefully. If the right side worked once, and these connections were altered, that's probably your trouble.
Do you have anything besides a DMM? Can it read audio level ac voltages so you can try to trace the audio signal?
Win W5JAG
Yes.
I hope not.
Indeed I was thinking about that.
Altered, no, but damaged during a short, yes.
Nothing else that I would consider plugging within this circuit for now.
Have we established whether you used AC or DC on your dmm when you took those readings?
The important fact here is that the other channel is, and has been working perfectly. The readings that you got were almost identical on both sides of the driver tube so I don't think that there is anything wrong with that.
The AC reading of a DC voltage on a good dmm should read nothing but one with poor half wave rectification on a rippled DC line could throw up readings like that.
Sent from my HTC One_M8 using Tapatalk
The important fact here is that the other channel is, and has been working perfectly. The readings that you got were almost identical on both sides of the driver tube so I don't think that there is anything wrong with that.
The AC reading of a DC voltage on a good dmm should read nothing but one with poor half wave rectification on a rippled DC line could throw up readings like that.
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Haven't really thought about it before, but is there a way to jumper or cross connect the two grids of the 12AT7? I'm at the office and don't have a board here.
Might need to use a blocking cap, but if the working left is jumpered to the input of the right channel, and the right channel works, the problem is external to the board.
Win W5JAG
Might need to use a blocking cap, but if the working left is jumpered to the input of the right channel, and the right channel works, the problem is external to the board.
Win W5JAG
DC Measurements
Here are the DC measurements for the driver tube:
P1: 238VDC
P2: negligible
P3: 1.82VDC
P4: (To ground): 58VAC
P5: (To ground): 58VAC
P6: 239VDC
P7: negligible
P8: 2.16VDC
P9: 27.3VDC
It looks like P3 is too low and P9 is far from the 100VDC example value given.
Not sure what's happening with the readings at P4 and P5.
Here are the DC measurements for the driver tube:
P1: 238VDC
P2: negligible
P3: 1.82VDC
P4: (To ground): 58VAC
P5: (To ground): 58VAC
P6: 239VDC
P7: negligible
P8: 2.16VDC
P9: 27.3VDC
It looks like P3 is too low and P9 is far from the 100VDC example value given.
Not sure what's happening with the readings at P4 and P5.
The DC voltages on your plates, cathodes, and grids look okay to me. 2 watts on one triode; 2.3 watts on the other.
I think it's reasonable to conclude your CCS' and tube are okay. Not sure about your AC voltages - you may have missed a decimal point on the filament voltages, but obviously the tube is working.
Look upstream of the input grid of the dead channel, assuming your output stage is working.
Win W5JAG
I think it's reasonable to conclude your CCS' and tube are okay. Not sure about your AC voltages - you may have missed a decimal point on the filament voltages, but obviously the tube is working.
Look upstream of the input grid of the dead channel, assuming your output stage is working.
Win W5JAG
The one problem I see now is the heater circuit P4 and P5. The reading of 58VAC is entirely too much. You should see 6.3V. This is Georges instructions.
The main filament winding should be 6.3 VAC at at least 5 amps. A center tap on this winding is OK, but it will not be used.
What kind of PS transformer are you using. Your tubes should be extremely bright with this kind of voltage. Are you sure it is 58VAC and not 5.8VAC?
The main filament winding should be 6.3 VAC at at least 5 amps. A center tap on this winding is OK, but it will not be used.
What kind of PS transformer are you using. Your tubes should be extremely bright with this kind of voltage. Are you sure it is 58VAC and not 5.8VAC?
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Too slow responding, I tend to agree w5jag.
Get some readings on those output tubes as well.