Help Identifying Problem with Laney LC30 mk1 and Solving it Hopefully

[ow81]

Hi,

I have a Laney LC30 mk1 1x12 combo that I've had from new, I bought the amp as a teenager after saving up my Saturday job money. I guess I bought it sometime between 1996 and 1997, so a good few years ago.

Anyway I've not really used it much for a long time but was thinking of buying something new but thought I might as well get it working well again as it's not a bad amp.

I've never replaced the valves so these are like 30 years old pretty much now so it probably long overdue.

The main problem I'm having is on the drive channel in particular when I'm playing the volume fluctuates, at some points it sounds right but then quickly fades then comes then fades and so on. The clean channel seems ok, or if the same effect is there it's miles less apparent to the point of being virtually unnoticeable.

So basically I'd be grateful if anyone has any idea what the problem is likely to be, and if a revalve will likely fix things. If not what is likely to need doing to get it working well again?

Many thanks in anticipation of your help, cheers

Owen

 

[Mongillo19]

Do you have a manual that would say which preamp tubes are associated with each channel? It sounds like if it's a specific channel, it is probably a preamp tube. Find out which one(s) correspond to the drive channel and swap it out.

Others are much more experienced in amp repair here but that would be my first move

Looking it up, I'd replace V1 and V3

 

[la szum]

What Mongillo said. If you don't experience that issue on the clean channel then
power tubes (V5 to V8 in the diagram above) are probably ok (even if I would swap
them out, just to be safe, and it is probably time).

Likely culprit is V1 or V3. Many preamp tubes share duties and do more than one task,
unlike power tubes.

 

[zerofucks]