• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

VTL250B ( Vacuum tube logic) keeps blowing main fuse.

Correct slo blo fuse blows instantly when unit is turned on. I removed the lower panel and observed that the amplifier was previously worked on . I suspect that the original resistors across one of the big power capacitors ( 400v 3300uf) were changed ( might have burnt ?) as they do not match the other resistors in the same amplifier and also when compared to the other good good amplifier. Also the weep hole at the bottom of the capacitor was covered with scotch tape. Another observation was that there was evidence of a leaky capacitor due to sticky residue on the bottom panel. I looked at the circuit board carefully and did not see any burnt components.
So would a leaky capacitor of this kind cause the main fuse to blow?
 
One of the power capacitors was bad. The diodes checked out ok. I ordered four new power can type , screw terminals, electrolytic capacitors to replace the old ones in both mono blocks. To confirm the bad capacitor I swapped them out and the amplifier did not blow the fuse . 3300 uf 400V