Gibson Medalist 4/10 - Bleed thru of signal w/volumes all the way down

[Helmholtz]

Not completely sure. With wires that close some capacitive coupling between the tube sections is possible.

[Greg_L]

I had a similar problem to this with a Fender build once. No matter what I did there was a small amount of bleed with the channel volumes turned all the way down. I tried everything. Nothing fixed it. What was the problem? Just crosstalk through things being close together. High voltage near signal voltage and no amount of chopsticking and lead dress tweaks could take care of it without redesigning the whole thing from scratch. I bet if you scoped the air near plate resistors you might see some signal in the trace lol. It's just the nature of the beast sometimes.

So what did I do? Just live with it. It seems like a problem but it really is a non-issue. No one plays an amp with the volume all the way down. As soon as you crack the volume open it sounds and works perfectly normal and off you go.

[Mars Amp Repair]

I had a similar problem to this with a Fender build once. No matter what I did there was a small amount of bleed with the channel volumes turned all the way down. I tried everything. Nothing fixed it. What was the problem? Just crosstalk through things being close together. High voltage near signal voltage and no amount of chopsticking and lead dress tweaks could take care of it without redesigning the whole thing from scratch. I bet if you scoped the air near plate resistors you might see some signal in the trace lol. It's just the nature of the beast sometimes.

So what did I do? Just live with it. It seems like a problem but it really is a non-issue. No one plays an amp with the volume all the way down. As soon as you crack the volume open it sounds and works perfectly normal and off you go.

Well, that's the conclusion that I finally came to also. As I imagine with you, it became a technical challenge aside from the 'total loss of profitability' of the repair! I viewed it as a great Sherlock Holmes moment (more like a 10hr moment).
Anyway it really was an acceptable level even if the end user was playing in an apartment at 2am and still could just turn the guitar volume down.

Still interesting as the layout was acceptable and you can see the component values eg Rp and Rk were standard Fender values for a 12AX7 which is what the 6EU7 essentially is. I did finally detect signal on Node 'F' but even a value of 220uf would not extinguish it and it was such a low level as to not be believable to create this issue.
Yeah I agree with you it was somehow just radiating into the air in the vicinity. We'll never know & the probability of seeing another one of these amps is equally as slim!

Thanx for the input...glen

[Mars Amp Repair]

Just thought: IWWEWD I wonder what Enzo Would Do! Sad he's left us...g