Paul Joppa
Moderator
That 1.2K is the fat resistors on each side of the driver socket. See page 66 of the manual for a picture. Are they the right values (1.6K and 4.7K)?
Completed Stereomour—left channel crackles/pops/hisses/distorts [solved]
- Thread starter funandfunny20
- Start date
funandfunny20
New member
Got new fuses, but I am still not getting any readings. Except, an odd reading is -reg, which is NOT 0—it reads .7 or something like that.
Just to cover my bases, the larger holes of the tube sockets are closest to the hum pots, right?
Just to cover my bases, the larger holes of the tube sockets are closest to the hum pots, right?
funandfunny20
New member
I also checked the resistors. As far as I can tell, they are correct. I have them exactly like they are in the pictures, including the direction of the words.
The most confusing part of all of this is that the amp worked (and sounded good) for almost two days…
The most confusing part of all of this is that the amp worked (and sounded good) for almost two days…
funandfunny20
New member
Any ideas?
Paul Joppa
Moderator
If the 1.2K resistance (1600 parallel 4700) is really 500 ohms, then it is being shunted by something. The obvious candidate is the bypass caps on the PSU board. This could happen if they are in backwards. You can disconnect the wire that goes into the board terminals marked "K" and then measure the resistance again to test this theory.
funandfunny20
New member
Removed both wires from the k terminals and I'm still getting the same results: A4, A1, C4, C1, and all the other points that are supposed to read 1.2k Ohms, only read .5k Ohms.
Any other suggestions? I'm thinking about just rebuilding everything. Is that a plan worth pursuing?
I'll attach some photos in a couple of minutes.
Any other suggestions? I'm thinking about just rebuilding everything. Is that a plan worth pursuing?
I'll attach some photos in a couple of minutes.
funandfunny20
New member
Paul Joppa
Moderator
Sorry to say this, but it's time to unsolder and detach one end of each of the 166K and 4.7K white resistors and measure each one by itself to determine which one(s) are actually not the right value.
It might be a good idea to check your meter with some other resistors to be sure the meter is OK and this is a real problem, not a flat battery or something! Try R1 and R2 on the C4S board, they can be measured without removing them.
It might be a good idea to check your meter with some other resistors to be sure the meter is OK and this is a real problem, not a flat battery or something! Try R1 and R2 on the C4S board, they can be measured without removing them.
I am going to go ahead and concur that there is probably a meter issue here.
If A1/A4 and C1/C4 all measure around 60V DC, then you're not going to have 500 Ohms to ground from those pins.
It would be helpful to see a shot of your power supply board, as there may well be a cap in backwards.
If A1/A4 and C1/C4 all measure around 60V DC, then you're not going to have 500 Ohms to ground from those pins.
It would be helpful to see a shot of your power supply board, as there may well be a cap in backwards.
funandfunny20
New member
Man….turns out my multimeter was terrible.
Got a decent one from radioshack and everything looks good…except OB and terminal 2 are only at about 70.
Also, R2 (the one closest to the transformer), flashed a couple of times. And my LEDs on that side do not light up.
What should i try next?
btw, Thank you Doc, Paul, and Paul!
Got a decent one from radioshack and everything looks good…except OB and terminal 2 are only at about 70.
Also, R2 (the one closest to the transformer), flashed a couple of times. And my LEDs on that side do not light up.
What should i try next?
btw, Thank you Doc, Paul, and Paul!
Flashing could be a sign of a funky solder joint, I'd start there.
Does the ~70V reading persist after the funky flashing? Is the flashing initiated by you poking in there with the meter?
Does the ~70V reading persist after the funky flashing? Is the flashing initiated by you poking in there with the meter?
funandfunny20
New member
Okay, re-soldered the R2 and now no flashing.
The voltage on T2 and OB still settles at 70v.
Is it bad to try it with speakers?
The voltage on T2 and OB still settles at 70v.
Is it bad to try it with speakers?
Paul Joppa
Moderator
OB at 70v means the 431 in the driver cathode on that side is shorted. You can test voltage at kreg; they should beoth be 2.5v but I suspect one of them is at 0 volts. Could be a short at the tube socket or on the PC board.
funandfunny20
New member
Both Kregs are actually 2.5.
I'll inspect the socket and the 431 right now. Could the carbon from the flex (between OB and IB) cause the short? I cleaned it off pretty good and it no longer sparks.
I'll inspect the socket and the 431 right now. Could the carbon from the flex (between OB and IB) cause the short? I cleaned it off pretty good and it no longer sparks.
funandfunny20
New member
funandfunny20
New member
I've removed the PC board. A simple resistance test between OB and IB yield 20.0. Whereas, a resistance test on IA and IB yields 0.0.
Does that help with anything?
Does that help with anything?
funandfunny20
New member
All my soldering looks good. Just in case, I re-heated all three joints of the troubled 431.
Should I re-install the PC board and test the voltages again, or are there any other tests I should try before?
Should I re-install the PC board and test the voltages again, or are there any other tests I should try before?
funandfunny20
New member
I checked the resistance of R1 (on the side where the LEDs are out) and it's only showing 4.3, whereas the other one is reading 237.0.
Does that mean it's fried? This happens to be the same resistor that was flashing…
Does that mean it's fried? This happens to be the same resistor that was flashing…
Paul Joppa
Moderator
Yeah, that's it. I can't imagine how it could have flashed, the current is small, but if it doesn't read 237 (or very close) it's toast and could easily explain the voltage reading.
There's no way to say whether replacing it will solve the problem, or whether some other bits may have been fried. It could be interesting to try - you can probably find a 240 ohm at RatShack or something locally - but I'd say the best bet it to get a replacement board and stuffin's.
There's no way to say whether replacing it will solve the problem, or whether some other bits may have been fried. It could be interesting to try - you can probably find a 240 ohm at RatShack or something locally - but I'd say the best bet it to get a replacement board and stuffin's.
