Faulty Laney VH100R

[metamatic]

Hi
i'm having some issues with a Laney VH100R head.
The problem is on the dirty channel (Channel B).
On this channel, when guitar is picked softly or with low gain (low guitar volume or low output pickup), the amp stutters and buzzes/pops, and the signal goes in and out and sometimes completely mutes. If i hit hard or with high guitar volume the sound gets in again. When it stutter it sounds as if i had a faulty jack cable
I replaced the preamp tubes and cleaned the tubes socket, but the issue is still there. The issue is only on channel B, channel A works pretty fine.
I suspect it has something to do with the channel switching relay....or maybe some faulty capacitor in Channel B signal path?
any idea?
This is a pretty old one, made around 1997

thanks, regards

[Steve L]

Here is a schematic package. I would look at the interconnect cables first, particularly the soldering on the pc board headers.

If you have the equipment, inject a very low level signal into the input and trace it out with a scope. Tap the board while you are doing this to check for an intermittent connection.

Steve

[metamatic]

thanks for your reply!
Actually i don't have the equipment to continuosly feed the amp with a low level signal and monitor it.. could i try with the computer soundcard?
I'll check the soldering on the PCB.
I thought it was the relay as sometimes it randomly changes channel
regards

[guitician]

That relay is suspect. See if you can jumper the contacts for the channel sputtering and see if it stops.

[metamatic]

Following the signal path with a probe i've been able to find a bad solder joint on one of the preamp tubes sockets. Just resoldered and works great!
thanks for your tips
regards