Mark iii volume drop

[seriesnuns]

Lately when I have been going from lead back to rhythm channel (1) I've been getting a volume drop.

It comes back and I would say it's not as loud as when I originally switched over.

Any ideas what can cause this.

Tubes have been changed recently.

 

[kdorsey]

How are you switching channels, foot switch or front panel?

 

[seriesnuns]

With a foot switch. Not factory through a loop master.

 

[kdorsey]

Disconnect all cables and external switches and switch channels with the front panel controls only. If the volume drop isn't there, the problem is probably a bad external switch.

 

[seriesnuns]

Still getting the volume drop with the footswitch using the push/pull knob.

I ended up adjusting the master up a notch.

I mainly play on channel 1, I'll put it the list to be checked out.

 

[McBarry]

If tubes changed, that leaves only a myriad of possibles.. LOL....unfortunately 99% of them result in internal exploration..

My very first instinct is a LDR going south.. as volume comes back slowly..

Doesn't sound very cold joint, and not many other parts "change" once signal applied...

But this is COMPLETE guessing... U need it on a bench unfortunately...

sorry can't be more helpful..
DB

 

[kdorsey]

Does it do the same thing using the front panel switches?

 

[seriesnuns]

Yea same issue using the lead pull switch.

What does LDR stand for?

The caps are also original inside the amp.

 

[McBarry]

Light Dependant Resistor or more correctly Optocoupler.
Google Vactrol 5C1 and have a squizz at the datasheet. Neat devices..