drastic volume drop on marshall avt 100

[geraint evans]

ive just replaced the chip located on the heatsink on my amp , that seems all fine
but theres something up with the conecter cables from the transformer power supply i think . when playing through the amp with the top opened i noticed the volume just kinda halfed its output , but when i (carefully) touched the cables from the transformer the full volume came back ?????? , but then after a few minutes playing it dropped again ???
but a quick tap with my hand on the side of the amp head brought it back again

Geraint

[Ronsonic]

You have already diagnosed that it is a bad connection. Now find and fix it.

Yeah, I know.