azrockitman
New member
We have ignition. ;D
stereomour 2A3's not glowing
- Thread starter azrockitman
- Start date
azrockitman
New member
I'm much closer ;D but I only have audio on the left channel. (I love the sound out of that one channel though.....can't wait to sort this out)
The problem is not a tube, not interconnects, not speakers, not speaker wires. Swapping any of those items only confirms the right channel is not working. My biggest red flag left, other than a couple of odd voltage readings, is that I can't get any reading when I try to do the hum balance exercise. If the hum pot is defective or wired incorrectly, will that kill sound out of that channel? or is that irrelevant.
Below are my original voltage readings, todays readings and the S.B. readings. I see the biggest differences on terminals 2, 4, 12, A3, C3, OA. The rest look either spot on or close enough. Is there anything here that would point in one direction?
PC boards, HV+, both read 374
The problem is not a tube, not interconnects, not speakers, not speaker wires. Swapping any of those items only confirms the right channel is not working. My biggest red flag left, other than a couple of odd voltage readings, is that I can't get any reading when I try to do the hum balance exercise. If the hum pot is defective or wired incorrectly, will that kill sound out of that channel? or is that irrelevant.
Below are my original voltage readings, todays readings and the S.B. readings. I see the biggest differences on terminals 2, 4, 12, A3, C3, OA. The rest look either spot on or close enough. Is there anything here that would point in one direction?
PC boards, HV+, both read 374
Since the solved problems were related to cold solder joints, one easy approach is to simply go over every joint in the amp (or at least on the bad channel) and watch closely to make sure the solder flows, penetrates the connection and forms a good concave fillet around the joint. Adding just a little bit more solder when you redo each joint is helpful.
If OA is zero, then no voltage is getting through that C4S.
You know you have voltage at IA, so the options are:
1. Cold solder joints on the PC board
2. A miswire from OA (it should go to pin 1 or pin 6 on the 9 pin socket, I don't remember which off the top of my head)
3. A short from OA (measure resistance to ground, it should be hard to read at all or very high, but nowhere close to zero)
4. A backwards LED
Let us know what you find,
-PB
You know you have voltage at IA, so the options are:
1. Cold solder joints on the PC board
2. A miswire from OA (it should go to pin 1 or pin 6 on the 9 pin socket, I don't remember which off the top of my head)
3. A short from OA (measure resistance to ground, it should be hard to read at all or very high, but nowhere close to zero)
4. A backwards LED
Let us know what you find,
-PB
azrockitman
New member
Thanks Paul,
I don't believe I have any cold solders on the PC Board
OA is correctly wired to pin 1
I believe I might have had a solder bridge between pin 1 and pin2 on the 9 pin socket, so I moved 2 slightly out of the way. But now I get 380 volts at OA, which is clearly too much by my interpretation...and it also seems to immediately cause a new problem below;.
My LED's are correctly positioned but where they worked prior to me moving the #2 pin away from pin #1.....now the pair of LED's on the A side no longer light.
I don't believe I have any cold solders on the PC Board
OA is correctly wired to pin 1
I believe I might have had a solder bridge between pin 1 and pin2 on the 9 pin socket, so I moved 2 slightly out of the way. But now I get 380 volts at OA, which is clearly too much by my interpretation...and it also seems to immediately cause a new problem below;.
My LED's are correctly positioned but where they worked prior to me moving the #2 pin away from pin #1.....now the pair of LED's on the A side no longer light.
380V at OA is more correct than 0V.
How is your Kreg votlage on that same side?
If those pins were touching, get in there with your wire cutters and trim everything down so that can't happen again.
-PB
How is your Kreg votlage on that same side?
If those pins were touching, get in there with your wire cutters and trim everything down so that can't happen again.
-PB
azrockitman
New member
OA is at 372 KREG on same side is about 22V
The other oddities at the moment are Terminal 2 is 370 instead of 230, terminal 4 fluctuates between 16 and 35mV, terminal 12 is around 33mV.
All others, including socket A and C appear normal/within tolerances.
OB is at 202 KREG on that side is correct at 2.5V
-REG is correct 0.0 on both sides
IA is at 373
IB is at 372
The two HV+ terminals are about 371 each
And I'm still scratching my head at what I did to cause the A side LED pair to stop lighting. B side remains fine.
Thanks for your help
The other oddities at the moment are Terminal 2 is 370 instead of 230, terminal 4 fluctuates between 16 and 35mV, terminal 12 is around 33mV.
All others, including socket A and C appear normal/within tolerances.
OB is at 202 KREG on that side is correct at 2.5V
-REG is correct 0.0 on both sides
IA is at 373
IB is at 372
The two HV+ terminals are about 371 each
And I'm still scratching my head at what I did to cause the A side LED pair to stop lighting. B side remains fine.
Thanks for your help
The TL431 is not working on the offending side, that could be the entire problem.
Can you double check that the jumpers are wired up properly? If so, you'd probably just need to yank and replace that 431, then the LED issue an output issue and OA issue may fall into line.
-PB
Can you double check that the jumpers are wired up properly? If so, you'd probably just need to yank and replace that 431, then the LED issue an output issue and OA issue may fall into line.
-PB
azrockitman
New member
Both TL 431's are wired with the flat side facing away from the center of the PC board, and the round side facing in towards the center. And the three solders on the underside for the TL look good/solid and clean to me.
I would suspect Fry's has them....as long as there is nothing especially unique about these, I can try to find one there first....looks like they're cheap.
I would suspect Fry's has them....as long as there is nothing especially unique about these, I can try to find one there first....looks like they're cheap.
azrockitman
New member
Fry's had none marked TL431, but the webernet implies that the NTE999 is equivalent. Can you confirm if it is or not?
http://www.nteinc.com/specs/900to999/pdf/nte999.pdf
Thanks
http://www.nteinc.com/specs/900to999/pdf/nte999.pdf
Thanks
Yes, that part will work.
-PB
-PB
azrockitman
New member
thanks!
azrockitman
New member
I've removed the old LM431 shunt regulator and have installed and soldered the new one. I have continuity between the two outside pins now when checking (there is no solder bridge....there is no continuity between either of the two outside pins and the center pin). That's true for both the new replaced one and the other one on the other side of the board. (there was no continuity on the outside pins prior to install) Is this correct/ok, as designed?
Thanks
Thanks
Yes, the two outside pins are wired together with the black jumpers on the PC board.
-PB
-PB
azrockitman
New member
Gotcha. Thanks
