Ampeg SVT 6 Pro shorted supply?

[booj]

SVT 6 Pro.pdf

Came in with 5 shorted outputs and a shorted 13v zener, which I replaced. At this point I can't find any shorts in the output section or the power supply. I can put a very few volts into the power supply from a variac to the point of drawing about 3 amps. At that point, I get voltage from the transformer secondary on all the windings. After a short time (pardon the pun) the bridge rectifier (which reads ok) becomes warm, so something is shorting. I'm just a bit tired of looking at this beast for the time being. Anybody got any ideas? Any help greatly appreciated!

[Enzo]

You are confusing "drawing current" with "shorting". Just because the circuit draws excessive current does not mean automatically that something is "shorted". An open resistor or cracked copper trace can easily leave a power transistor turned full on.

Are R16, R17 open? Your main outputs run on +/-65v rails, but are the two 100v rails healthy? Those power the drive circuit. Are Q3,Q45 OK? Is bias ckt OK? Q2, R10, R11, AP1?

Did you check for opens on all those 5 watt 0.47 ohm ballast resistors? And did you check all of the 47 ohm gate resistors?

[booj]

Ok! I have more information. I don't know the exact chain of events other than the amp being run hot on a hot day, but I did find that Q6 was shorted, which is directly connected to D6, the 13 volt zener I had replaced. Q6 is connected also to R139, R119, R118, R117 and R27, which are all discolored and off value. (about 33k instead of 22k) Everything else looks ok. (of course I thought that before). So... questiion is now after I change these components any suggestions on what next? Or just try it again? Q32, Q14, Q13, Q12 and Q11 have already been changed along with their respective .47 ohm resistors. Bias circuit is ok. Haven't checked Q3, Q45, R16 or R17, but will presently. Thanks for your response Enzo!

[booj]

The 5 outputs, their 47 ohm and 2.2k resistors, Q6, and C10. That was it.