I just wanted know what would be the best way to test this transistor. Should I just do a diode test between the collector & emitter instead of the normal method of transistor testing?

 

My 2¢: I often the base-emitter and base-collector junctions as if they are diodes. Given that the base circuit in your transistor is made of two 10k resistors, the diode check might not give definitive resullts. Alternatively, I would try injecting base current (voltage through the resistor network) to see if that results in collector current increase.

 

This device has built-in resistors, it will fail a standard "diode junction test" with a multimeter.

Connect the Emitter to 5V and ground the Collector through a 220 ohm resistor.
No current should flow, now ground the Base- current should flow.

 

Owner said this unit was working, put in storage for 3 months, took it home, plugged it in and no sound. Maybe he forgot to tell me something.... I dunno but I have to say it is a really nice system. Not your typical boom box.

I've hit a wall, well sorta. It just doesn't make any sense. I tried replacing the 2 transistors in question & the Audio IC. Still no sound from the speakers, everything else works fine including the headphones. Speakers are good. All fuses are good. Have voltage on the amp board, all components on that board checked out ok. Protection relay for speakers is working as it should, no voltage. I haven't checked the headphone port as a possible cause yet but it's next on the list.

I haven't worked on many Audio devices, I do not have a signal tracer but was wondering if there is a way to safely use my scope to trace the speaker outputs from the outputs inward for a signal? This is the system : https://www.manualslib.com/manual/1594877/Sony-Hcd-Zx66i.html?page=25#manual.