Marshall Valvestate 15 Problem

[lakesidepark]

Hello guys recently I bought a used Marshall VS15 (8015), but sometimes the sound fails, and I don't no how it happens. I'm searching for a schematic or a service manual from this amplifier.


Please help me.

Thanks

[karul]

http://schems.com/bmampscom/marshall/

Valvestate 20 schematic is available. Take a look at it. They should be similar.

What's inside V15 ? LM1875 or TDA2030 ?

[lakesidepark]

The valvestate 15 have 2 gain, linked each other, and uses LM1875, but my problem is between , before the tonestack.

[EddieTavares]

Can you talk about that fail? Does it mute the amp?

[lakesidepark]

Sometimes when i'm playing appears a hum and the sounds become saturated, and the bass control has no action when I turn, and the mid pot work like bass pot on/off.