Hot Rod Deville III V1 random noise and oscillation.

[jvm]

Hot Rod Deville III making random noises and will go into oscillation when bright switch is engaged. I can touch the insulation on the right shielded cable from main PCB to V1 and stop the oscillation. I have checked both shields, resoldered the ribbon cable. Problem persists. Anyone else seen this?

[nickb]

Hot Rod Deville III making random noises and will go into oscillation when bright switch is engaged. I can touch the insulation on the right shielded cable from main PCB to V1 and stop the oscillation. I have checked both shields, resoldered the ribbon cable. Problem persists. Anyone else seen this?

That suggests to me that the screen of that co-ax it not not making a good connection to ground. Carefully check the connections.

[52 Bill]

And the all too common bad decoupling filter cap for the preamp stages.

[jvm]

Thanks guys. I replaced the pre amp filter cap first, no change. I then replaced the ribbon cable with individual wires and problem solved!