q7418 is the driver transistor
q7425 is the biais transistors
q7420 q7421 are what we call a differential pair transistor amplifier
if the 22 ohms have busted i would check all the transistors outside the circuit up to the driver, the output transistors are darlington, they may be tricky to test thru a diode test, since the junction voltage is twice a normal transistor and you have an emitter emitter resistor in them
The biais voltage may got to high, cold solder, mecanical failure etc ...
i had a similar problem in the past with the biais circuit, it got defective and busted out the amplifier section, since it was direct coupled lots of parts failed ....