Fender M-80 112 non chorus channel bleed

[jvm]

I have a fender M-80 112 combo ( no chorus). When the clean channel volume is turned completely off, I can hear the drive channel through the speaker. The drive ch gain control will increase or decrease the amount of gain while this is happening. No other drive channel controls have any effect. The amp has all new electrolytic caps, MC14053 IC has been replaced. The amp functions normally other than this one issue. Any help at all appreciated

[jvm]

Here is the schematic: Fender M-80 HM Series.pdf

[Enzo]

You can hear it when the clean controls are at zero? And presumably you have CLEAN selected? I have to ask: is it a problem? I mean when you are in clean and playing, does this extra sound still come through? You have a little crosstalk from the high gain stage. Just where it is happening is a good question, I have no idea.

Your schematic is for the Chorus model

M-80 HM Series.pdf

[jvm]

Ooops, my bad on the schematic! Thanks for posting the correct one, Enzo. It is an issue because when playing the clean channel with the drive ch gain turned up, both are present in the output. Makes for a "dirty" clean.

[g1]

How about if you jumper the OD vol. pot wiper to ground, does the dirty sound still bleed through?

[jvm]

Update: Through signal tracing I've determined that the OD channel signal is NOT bleeding into the clean channel. It is somehow getting to the power amp in addition to the clean channel signal. It is not present anywhere in the clean ch circuitry. I have it at both sides of R62 through C35 and at Pin 6 of U6. It is not present at U3 pin 1.

[g1]

So it is only appearing on one side of R61?

[jvm]

Correct, g1. It is present at the junction of R61 and R62

[jvm]

Still present at R62 with Drive ch volume wiper grounded.

[Helmholtz]

Lower side of R62 should be grounded via the switching ext.speaker jack.
If there's signal, check the grounding path/contacts.

[jvm]

I checked for ground at the ext jack.The shorting contact was not making good connection but I grounded the lower side of R62with a jumper. It seemed to decrease the distorted signal VERY slightly but the problem persists

[g1]

Under same conditions as #8 above, plug a cord into the PA in jack, do you still see that distorted signal at R61/62 junction?

[jvm]

g1, Grounding BT5 with a jumper and inserting a plug into power amp input actually increases the volume slightly but distorted signal still present.

[g1]

This is still using the regular input and just an empty cord plugged in to PA IN jack?

[Helmholtz]

See if relais U5C grounds the lower end of R27 in clean mode.