V4B - Standby switch doesn't work / cut power

[Roman Ships]

A while the standby switch stopped functioning. The amp was just "on" with the power switch.

I replaced the switch, didn't fix it.

I have opened it up and thought I had found a bad D5 diode but I tested it in circuit again later and it tested fine. Probably just tarnished / corroded surface and my DMM wasn't making a good connection.

I know the standby lifts ground on the filter caps after the first Cap. I haven't found any obvious grounding issues. I did find a screen resistor that was loose, pretty much just sitting in the socket, not connected. I assume it got very hot and un-soldered it self. According to the schematic, it looks like I should have plate voltage on standby, I do... is this correct?


Before I tore it apart I think I tested voltage drop across plate resistors and V5 adn V6 were pulling waaay to much current. They look like they have been very hot, the JJ text looks burnt.


I am in the process of updating screen resistors, grid stoppers, one original filter cap ( C17 ), the rest are JJ filter caps.


There was some charr / gunk on the back underneath the screen resistors, was I getting some conduction over that perhaps?


Thanks,
eli