Peavey 400BH blows fuse

[Memphis]

I have a 70's Peavey 400BH that blows the fuse after about five or six seconds of being turned on. I can hear it draw down power on a small fan I have plugged into the same outlet. Any Ideas

Bruce

[Twist]

Have you got a schematic and do you have any basic electronics experience?
Soldering skills, using a multimeter...etc

[Enzo]

Answer Twists questions first. I'd be expecting shorted output transistors.

Schematic

[Memphis]

Have schematic

"Have you got a schematic"

Yes.

and do you have any basic electronics experience?
Soldering skills, using a multimeter...etc

I have built my share of tube amps.

I checked all the output transistors (by removal) All appear to be good.

Bruce

[Enzo]

Isolate the problem.

Disconnect the secondaries from the board - the oprange wires, and the red wires - and power up. Does the transformer running alone like this still pop fuses?

Look up "light bulb limiter." Make one. Use it.

Or use a variac and ammeter.

If the transformer is OK, connect the orange wires. only. Blow or no? Then the red ones.

All outputs "appear" to be good? None measure shorted on a meter?

Check ALL rectifier diodes in the powr supply. ANy shorted?

Make sure CR9, CR13 are not open, and that the connections to CR13 are OK.