Hartke LH 500 blowing fuses.

[GainFreak]

A friend of mine brought an LH500 with the same symptoms so I''m posting in this old thread.
The amp started blowing fuses after it fell during rehearsal. I'm more into tube amps and have little experience with SS amps so bear with with this one.
When disconnected from the main PCB the rest seems to be working OK and amp doesn't blow the fuse so it looks like a power amp problem.
The speaker output measured open circuit. All transistor on top of the heatsink measured ~1 Ohm between all 3 legs. I lifted only one of them from the PCB and it measured OK. The SA1837 on the heatsink measured short circuit between emitter and collector. At this point I'm wondering if I should measure all of the transistors individually? Any advice would be appreciated.

[Enzo]

Hi, Gain. Really, start a new thread for your repair.

[Jazz P Bass]

All transistor on top of the heatsink measured ~1 Ohm between all 3 legs. I lifted only one of them from the PCB and it measured OK. The SA1837 on the heatsink measured short circuit between emitter and collector. At this point I'm wondering if I should measure all of the transistors individually? Any advice would be appreciated.

Yes.
The transistors are in parallel.
So one or more shorted will show up as all shorted in circuit.

LH1000 v3.8.zip