Marshall Valvestate (VS100) Low Power Output

[l600dan]

Hi there, I've just bought this amp on ebay in good faith but there appears to be a problem with it. After turning it on and allowing it to warm up, the power output seems ok for a split second and then reverts to being very quiet (so quiet you can talk over it). The output doesn't even seem to get any louder when you adjust the volume and/or gain settings either.

It is the same on all channels. I've noticed that turning the gain right down and then up a gnats cock it seems to sound more beefy but only until you try and turn it up and then it reverts to being quiet. Tonally, it sounds good.

Any ideas? Also, if this requires attention over and above my capabilities - basic electronics, how much is this likely to cost to repair?

Cheers

[Twist]

Try plugging a short patch cord into the effects loop (output to input). Do the same thing to the pre amp out and power amp in if it has those in the back. I'm not familar with other shops fees. I would guess anywhere from $35 to $100 depending on the problem.

[amptech]

marshall low out put

Hello there,

check for dry solder joints and use switch cleaner in all the pots and check if any of the resistors that may have gone high ohm reading.
try to get the diagram to 'see' what's going on with in the unit befor rushing it to the repair shop as they like to over charge for a simple repair job!

cheers