[Radio Wrangler]

It could be any of the transistors, so if going down that route, you could start anywhere.

Bootstrapped collector load is a popular way of increasing the voltage stress on the VAS transistor beyond what most people would guess it has to endure. It also serves as a handy route for importing loudspeaker disconnection transients and routing them to the VAS.

VAS transistors have a hard life and ideally you want one safe from 'second breakdown' conditions.

There's probably a good case for fitting an entire set of semiconductors to the suspect channel as a single operation. It dodges the endless circling blowing and replacing the same devices over and over again which is yoour fate if you try power with any dead (even recently killed) devices still in place.

David