Help with Delta AP-396AM TV power supply

[ravve]

My Sony 85 inch TV from 2019 stopped working. Troubleshooted the error to the Power supply board, where the 3,3V standby voltage is completely missing.

I am used to pinball repairs but never got into repairing power supplies.
I would really love to fix this instead of bying a new board, but need some guidance.

The power boad is a DELTA AP-P396AM GL93, (1-001-394-11).
Any schematics would be great but I can't find any.

What's done so far, with board removed from TV:
Main fuse OK.
Voltage over power cord connection (incoming) OK.
Resistors OK.

Most diodes including the zener diodes and some other components are testing short!
Used a thermal camera and noticed a diode (nr1 in pic) that was significally hotter than the others. Removed that diode from circuit and indeed it tested short. Now the diode next to it didnt test short anymore, however it gives strange increasing values (at diode test with DMM, board not connected to power). I guess I'll go ahead and replace that diode as well.

However, all other diodes etc are still testing short, which makes me think that more components are broken, am I right?

Any help to where to go from here is appreciated, also schematics, video links.

I am suspecting the IC DDA010 (number 2 in pic) as it also showed hot on the thermal camera. How do I test this IC? I know some ICs could be tested by diode test method? Tried to measure voltages at different components, like pin2 of the IC (Vcc in) but nothing...
But really need help to know what to measure

[R_J]

Re: Help with Delta AP-396AM TV power supply

I'm not sure what you are using to test the diodes but it is not working, I would start by checking the voltage ACROSS each of the two small electrolytics near ic901 (C904, C907?) I cant make out the designation. One of them is the start cap which will have the vcc voltage for the ic.

[ravve]

Re: Help with Delta AP-396AM TV power supply

Thanks! I'll check that out, but I need to forst replace the shorted diode I guess.
Here's a video showing contuety testing beeping on mostly the small black (diods?) With locations marked with FBxxx. I'm sure there must be a short somewhere, or am I doing wrong? (The shorted diode is removed in the video):

https://youtu.be/4yXOOKzcREk?si=yrFOSXkcoQzqg1dq

[petehall347]

Re: Help with Delta AP-396AM TV power supply

they dont appear to be diodes .

[R_J]

Re: Help with Delta AP-396AM TV power supply

You don't use BEEPS to check components, for semiconductor junctions use Diode test, for resistors use the resistance (ohm) scale

[CapLeaker]

Re: Help with Delta AP-396AM TV power supply

Also look at the voltage drop on the meter while you are in diode mode. Don’t use the beep / continuity function of your DMM to test components. Period.

[ravve]

Re: Help with Delta AP-396AM TV power supply

Thanks everyone! So just to double and tripple-check what you are saying:
These two babies shown in the pic ("GT3") aren´t these diodes? Because if I put the DMM in diode test mode, it tests short for both diodes. I´m pretty sure it should test like a normal diode, like ~0.5V in one direction and OL in the other direction. It simply shouldn´t show 0 ohms in continuety mode (beep), unless I´m doing something wrong here?

[stj]

Re: Help with Delta AP-396AM TV power supply

looks like a GDT a gas discharge tube.
is it across the transformer pins?

[R_J]

Re: Help with Delta AP-396AM TV power supply

I suggest looking at the trace (bottom) side of the board, you will see the GTx are across FLx coils (in this case the coils are basically a piece of wire)
Start by checking the Resistance of R915, If it checks open, ic901 will be bad as well

[R_J]

Re: Help with Delta AP-396AM TV power supply

Are you sure you checked the correct pin, CN6401, pin5 for stby3.3v, (there are 28 pins) you can check the standby voltage on jumper wire J168 (located between HS5 and C120A)