GT not booting up

[bdoi]

Hi
I have a gt with a non booting issue (no sound,no screen)
I was modding it with a composite video mod pcb.
It works short time but the screen was washed out ( colour to bright and jailbar.
It worked fine before , was recapped...
I checked again my wiring at found nothing bad.
Just find Q506 was getting really hot.
 Do you know replacement part number for this transistor?
Do you know if there is a possibility to start the console by feeding 5v somewhere ( no need the high voltage for the backlight now)?

[Keith Courage]

So the screen stays Black or does it show a solid White image when powered on?

[bdoi]

Screen stays  black . Really quick led flashing ( not enough to illuminate the screen) when I switch on but nothing more

[Keith Courage]

This might sound silly but make sure both 4.7UF caps were replaced with 4.7uf. I've seen a few where people accidentally put a 47UF on one which caused the problem you are having. I also did that myself once on accident.

[bdoi]

I will check it tonight . You spoke about the caps for the jailbar fix  ,right? Because the other 4,7uf are good because the GT works great after recap.
Which are the original values of the 2  caps for jailbar fix(C709 and C715)?

[Keith Courage]

Oh, I thought you said that the system worked good before the recap. So I meant the Two 4.7UF electrolyte caps. 

[bdoi]

Just checked and the 4.7uf caps are ok.

[Keith Courage]

The screen turning off immediately could also be a bridged solder joint. Meaning there could be a positive touching a negative somewhere. Maybe go back and check those Jail bar fix caps to the on the safe side.

[bdoi]

Édit : it was indeed a bridge solder joint on the  C709!
Thanks Keith!