As you may know, that to understand the Mosfet, Cascode, Hybrid, Class A tube amps are complex - I have my way of resolving some serious failures. Not recommended for the weak-hearted. A simple capacitor could blow your head into the wall, and leave a scar for the rest of your life. Electrical charges remain in your amp even when it is off, and carry voltages unimaginable for amplification purpose.
I have a service rate for basic checks at $80. Parts are additional.
If the basic checks won't help, then the service to do some serious checks are at $120, usually involving circuitry, component level failures and bypassing CAD/CAM designs on mainboard. Again, the parts involved on top of the advanced checks are additional cost.
Let me know how you need me to proceed. But if you think you want to sell it faulty at a loss, by all means because all repairs do not mean 100% original condition, and there could be other related failures coming along, akan datang buddy! The choice is yours.
Hope that helps....