86 Carvin X100 trouble.No Volume,cooked resistor

[gary]

OK I now have a slight signal from the speaker on the clean channel only,louder than to begin with.

The A6 4049 chip blew the bottom off of it.Still may have trouble there.The cap I replaced in the EQ board was good.No more hot components.

What should the - end of the big 22uf 500 volt cap voltage be?

I still dont think a signal is getting through the pre amp.Heres the voltage on each 12AX7 pin.

V1

1. 192
2. 0 !!
3. 1.3
4. 2.8
5. 2.8
6. 182
7. 0
8. 1.3
9. 2.9

V2

1. 279
2. 0
3. 2.9
4. 2.9
5. 2.9
6. 186
7. 0
8. 1
9. 2.9

V3

1.281
2. 0
3.
68
4. 2.9
5. 2.9
6. 280
7. 62
8. 68
9. 3

[Enzo]

Something happened to your +V rail. I am betting it was touched to the tube voltage at some point. it is not regulated, so it is not like the 25 hit the 15 or something. Two blown ICs - at least - could only happen by some overvoltage. ANything else on that line could have been stressed.

REplace the 4049 and then check the rest of the ICs for heat. Check all the op amp output pins - 1 and 7 - for DC. Looking for a few volts as bad, a few millivolts we can ignore.replace any with DC outputs.

500v caps? WHo knows, maybe 450-480 on the group after the standby switch, and lesser amounts at the later ones. I doubt it will be wrong. it will be there or not, pretty much.

What's wrong with V1, V2? Look OK to me. You sure you got zero volts on pin 2 of V3?

COnsidering your low voltage supplies were burnt up and you have so far discovered a couple blasted out chips, I sincerely doubt your tubes are at issue here. Frankly I expect you to find more dead op amps. They are 4558 or TL072 or something similar - generic op amps, and they cost 20-30 cents each from Mouser. At this point I'd probably just replace them all it if were mine. And sicne teh gates of the switching FETs are ultimately off the +V rail, some of those might be damaged as well.


After ther is no more DC, then apply a strong signal to the input and follow it through the amp. I am assuming you have no scope, so set your meter to AC volts and follow the signal with that.

[gary]

I replaced all op amps and my clean channel is working fine.

The pot switches wont change the channel and no LEDs.