EVO car radio -blank screen

[Cornboats]

I've had this in my Isuzu since I bought the truck in 2003. Stopped working and now on my bench for fault finding. Fuse at the back of the set is ok, testing using a 12v DC supply. 1st port of call was a disable button that you can remove which is supposed to deter theft. Looked at this first. When you insert it shorts 2 pins to make a circuit. Shorted pins out with white wire just to confirm.
2nd was the volume control which is pushed to activate a momentary switch to turn on /off. Test ok with ohmeter but ran white leads from pins just to check. Voltmeter shows 4.8v on to one of the pins and on both pins when button pushed.
Visual check on main circuit board and diode tested transisitors / fets I can see.
Now I'm stuck. Where do I go from here. Any help and advice would be greatly appreciated.

[stj]

Re: EVO car radio -blank screen

clarify,
"blank screen"

does the front light up? does it output sound?

[Cornboats]

Re: EVO car radio -blank screen

Nothing happening. No sound, no light. If you take out the removable button the led flashes, which its supposed to.

[stj]

Re: EVO car radio -blank screen

check the soldering on the power amp, some of those include a fet-switch to control power
and check any crystals or resonators are running

[Cornboats]

Re: EVO car radio -blank screen

Just an update. I found a transistor BD438 with a shorted leg. I've replaced but still have a dead set. There are 3 voltage regulators on the board 1 of which is adjacent to the transistor BD438 I've just replaced. I'll test these with the voltage on next. There is a smd transitor 3F P23 connected to the BD438 which is giving correct readings but then so was the BD438 until I pulled it. I'm reluctant to pull the smd transistor for fear that being so small I'll never get it back.