Looking for Marshall VS100 schematic

[methodofcontrol]

i've got a marshall 1x12 combo here, my friend found it at the curb w/ some garbage while walking his dogs. i told him i could probably fix it for him.
anyway, it makes sound, but not very loud. with everything up all the way you can still talk over it. but all of the EQ and volume controls and buttons seem to be responding as they should. i tried it through another speaker and w/ another 12ax7, neither helped the issue. i plugged a signal generator into the return of the effects loop and still had the same issue, so i'm guessing the problem is in the power amp.
i'm looking for a schematic so i can check voltages, and if anyone has any suggestions as to a likely culprit, that would be great!
thanks.

[Enzo]

I doubt it is voltages. Check the cutout contact on the headphones jack - the sleeve one, not the tip or ring. That is the speaker return to ground. Not only that, but there is also a 0.33 ohm 7 watt resistor between that jack and actual ground. Make sure it is not open or come free of the solder. R29.

There is also a small JFET type J111, T16 on the board. it is a mute, try removing it and see if the sound is restored.

If Schematic heaven doesn't have it, send me an email with Marshall VS100 schematic as the subject line, to:
tmenzo at msn dot com

[methodofcontrol]

hey enzo,
i found the schematic. i thought i had already checked that site, i must've missed it the first time around.
i took your advice and checked out that resistor and the mute FET, no luck w/ either of those. it had been a while since i listened to the amp, the sound it makes is actually whisper quiet. if you push the "power dimension" button and crank all knobs to 10, you can hear it a little better but you can still talk over it easily.
any other ideas on this one? thanks for the help.

[Enzo]

And the headphones jack ground cutout contact? Reach in with a small screwdriver or something, a meter probe even, and just press down on the sleeve contact of that jack. That will press the contacts together. If it restores the sound, there you go. For that matter, check the solder under every jack.

Make sure none of the pots are cracked.

Otherwise, apply a signal at the start and see where it disappears. If the power amp is suspect, then start there and work back.

[Amp Kat]

Also try connecting a cord from send to return. Does sound like a connection problem.

[Enzo]

And those are just quick checks, obviously as men of science, we would invoke the mighty oscilloscope and see where the signal collapses. For example, in my headphones jack scenario, the signal would be full strength at the actual output bus, but would not make it through the speaker.