1969 Deluxe Reverb blowing filter cap

[g1]

I changed the bias cap and adjusted the bias pot to a reading of -35v. With the new one it goes from 20 to 0v in regular intervals (i guess its normal).

Sounds like the vibrato is running. Disable it with the footswitch or at least turn the speed and intensity to zero.
As Steve suggested, see if the B+ drops with the power tubes removed.

[52 Bill]

Sounds like the vibrato is running. Disable it with the footswitch or at least turn the speed and intensity to zero.

If you are thinking that the trem works by fluctuating the bias voltage, Deluxe Reverbs use an opto isolator.

[g1]

Yep, my mistake, thanks Bill.

[Murdrak]

I finally figured it out guys. One of the primaries of the OT was shorted to ground. It was hard to see beacause I was taking readings with the transformer out of the chassis and everything was ok. The guys who rewound it hurt the wire insolation when they were putting it back together.. A little bit of tape and now it is perfect. The weird thing is that now I can't get a current reading to set the bias using the shunt method. I set the DMM to read mA with one probe to the CT of the OT (red wire) and the other to one of the primaries going to the tubes (pin 3, blue and brown in this case). I know this is not something wrong with the amp but something with the readings. You think my DMM is burned??

[g1]

Yes it is possible. Is there a fuse in your meter for the mA range? Also it must be DC rather than AC mA.