HK 930 receiver blows right channel speaker fuse.

Can anyone shed some light on this problem for me?

I resurrected this receiver from a totally non-functioning state due to some heavy-handed component butchery by persons unknown.

After getting it to play again, the right channel speaker fuse (3 amp) on this unit blows periodically. I haven't yet caught it in action but from time to time I will notice that the music is flat somehow and then discover that the right channel is out due to a blown fuse. Replacing the fuse brings this right channel back to life, but this only lasts for a while, days or weeks or hours of real time, probably within hours of actual play time. The volume knob is always well below half-full when this happens.

The fuse is in parallel with a 2200 ohm resistor, directly in line with the positive speaker output.

This unit has two separate power supplies, one for each channel.

The tech manual for this unit is in PDF form here:

http://manuals.harman.com/hk/Service Manual/HK930 sm.pdf

This manual has the schematics.

I am an "as-needed" junior techy. I have fixed various receivers and amps, read schematics, know how to use a multimeter, have a basic grounding in electronic amp circuitry, but I don't do this for a living or on a regular basis. I am hoping to get a heads up on what to investigate given the symptoms.

I expect the problem is somewhere in the power amp section.

My first guess would be the power output transistors, but I am wondering if these can be working correctly but overdriven to the point of blowing the speaker fuse due to incorrect voltage being supplied to the base of one or both output transistors (they are two per channel).

I am unsure if this kind of problem be caused by a fault in the power supply.

Also, this is a 60 watt amp. What size and wattage of resistor would work as a dummy load?

Any help gratefully accepted,
Jack
.

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