AVT 150 problem please help me

[gtv-gr]

Hello

My avt 150 was playing great sometimes ,others (very few) the sound got very treble and loss of bass and distortion , one day i left my hot laptop on the top of the air intake of the amp and since then the more treble -less distortion issue is PERMANENT i changed the valve with a new one still the same , what part of the amp is at fault?

[Ronsonic]

I've worked on a few of those and I can't tell from here. This will need a more complete diagnostics drill.