what has likely happened is that when someone replaced the filter caps, they just hooked the negatives all directly to ground. shorting out the standby switch and D5.
Take a look at all your main reservoir filter caps and the screen supply filter caps
and make sure that they are not grounded directly to the chassis. they should go to the standby switch which then goes to D5, that goes to ground.
Take a look at all your main reservoir filter caps and the screen supply filter caps
and make sure that they are not grounded directly to the chassis. they should go to the standby switch which then goes to D5, that goes to ground.
(02-26-2016, 08:55 AM)Roman Ships Wrote: 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