Blonde Bandmaster 6G7-A bleeding sound

[tribi9]

I got a blonde Bandmaster that was serviced by the local amp "guru" in 2003.

The old cardboad bias caps were left in the amp, the death cap was never clipped out and the ground from the AC was bolted on to the PT not even using a lock nut. I was able to loosen it by hand.

I had a quick look last night inside and it looks like

Only the filter caps were replaced and the cathode bypass caps on V1 and V2.

The amp still has all of the yellow and blue astrons tho.

The problem is that the amp is bleeding sound when the controls are at zero on both channels.

What should be the first thing to look at here?

Could it be the ceramic disc caps on the tone stack that are leaking. Are these little ceramic discs prone to issues

Could it be a leaking Astron? I dont want to replace any of them unlessit's absolutely necessary.

The only way I know how to test for DC is to lift the grounded leg of the cap. Is there a less intrusive way?

Thx all.

[kwijabo]

what does bleeding sound mean? more white noise, or do you mean when you have volumes on 0 that if you strum your guitar sound comes out?

if its the latter, i would think to look at the pots. contact resistance could've built up and when you're on "0" you actually have some resistance to ground that your signal is dropping across.

if its the former, i'll defer to those with more experience.

[tribi9]

It's sound coming through (very faintly) when the volume knobs are at zero on both channels.

[Structo]

Could be faulty pots or conductive circuit board.

[tribi9]

If it were a faulty pot say on channel 1, that would only make channel 1 bleed sound tho? Wouldnt it Structo?

[Andy Le Blanc]

a conductive waxed/paper component board can do some weird things.
so can a worn taper in an old pot., if you like a beat old amp, its part of the charm..

[vibratoking]

I'd never run that amp on zero anyhow. You shouldn't even be aware of the 'problem'.

[tribi9]

As it stands am only replacing the bias caps and clipping out the death cap. Will test after, maybe it will somehow magically stop bleeding the sound.

[Structo]

I've seen new pots and old pots do some weird stuff.

I would measure the total resistance and then the sweep.

[tribi9]

I opened up a cts pot a few weeks ago and cleaned some melted solder that had gotten inside through me bending and soldering the grounding tab onto the casing a while back. (I just run a thin wire now)
The pot worked, except for this little "bump" where it would go silent and the fact that you could get full volume on both ends of the rotation.

It works better than new now

[tribi9]

What is the reason Fender tied the cathode to pin 1 on some octal sockets? Was it just because??

[ChrisM]

What is the reason Fender tied the cathode to pin 1 on some octal sockets? Was it just because??

Probably an after market mod to run EL34s.

[tribi9]

Thx ChrisM, that's what i thought at first but the original schematic for the 6G7-A, shows the 2 pins tied.

i guess Fender knew people would experiment with different tube types hehee..

[Firestorm]

Thx ChrisM, that's what i thought at first but the original schematic for the 6G7-A, shows the 2 pins tied.

They were doing it before anyone heard of EL34s; habit from olden times - on metal 6L6 and 6V6, the metal case comes out to pin 1.

[tribi9]

Aaah, that makes sense.

Thx Firestorm.