Marshall vs100 ground issue

[charlie13]

I had a post on a dead channel but now it works two bad voltage regulators and a zener diode. Now a new problem when i reconnected everything it worked but the sound was almost not there. After some probing i found if i disconnect the ground wire (pin 7) on the ribbon cable between the preamp board and the daughter board the sound comes back but reverb and effect loop control are gone plus i get no sound if i press the power dimension swith and a tinny sound if i press the effect loop switch. I have found i get about 1.5v dc comming through the ground from the daughter board that i dont think should be there.
And since i cant ground it correctly i get some open humming. Any advice would be great im so close to getting thing fixed i can taste it.
Thanks
charlie

[Amp Kat]

Try patching a cable from send to return. Then take the send out to the front of another amp or input. Does it sound right ? Take a signal from another amps send to the return and see if you get power. We're basically isolating the problem to preamp or poweramp.