Hartke A35 Repair problems

[g1]

Yes, any transistors without plastic backs that are mounted on the heatsink need an insulator.
If the Q9 collector was in contact with the heatsink (ground), that probably explains the excess current through Q4 (via R97).

[Jesse]

Thank you! Things are looking much better!

Replaced Q4, insulated Q9.
Shorted input
No Load
Variac at full AC voltage 120VAC
1.03VDC across R97
0.29VDC at output

Is there anything else I should check before testing again with the 8ohm load?

[g1]

Sounds good.  Try it with load.  Some amps have trouble starting up loaded while on the bulb limiter.
If you get a bright bulb when you power it up loaded, you will have to power down, remove load, and power up.  Then (if bulb dim again) connect the load while amp is running.