Sony XR-65A95L no power due to logic board issue

[joliver82]

Hi guys!

I'm trying to repair a TV that a friend gave me recently. Lightning struck next to his house and broke the TV apart from more electronic devices.

First of all I've checked the power supply and it works as expected. I removed the logic board and shorted the 3.3v standby output to TCON_ON and POWER_ON and every voltage was generated as expected (12v and 25v for logic board and 32v for TCON).

When trying to boot the TV normally (having the board connected), the TCON_ON signal is not generated from it which made me think there's some issue in the logic board.

I've been checking it and I've found two potential issues. First of all I found two burned SMD components which I need to identify. Both are located near one of the HDMI ports, so I searched around the other HDMI ports and found the same components. I'm attaching pictures of them (the non-burned components) in case you can help me identify them:

I'm talking about the 2 pin component marked with "F2". This one I think it's a diode but not sure which.


Here I'm talking about the one marked as "D·I€". Probably a transistor? The pin below right is connected to ground, just in case this helps you.


Any help identifying the components is appreciated

I've been reviewing the whole board. All fuses and 0 Ohm resistors are OK. I've looked for shorts also checking all inductors and capacitors. The only weird stuff I've found is the output of what I think is a buck converter which has 1ohm resistance to ground. Attaching picture also:


Just after writing this message, I found out that the IC MPPK 8794 is MPS MP8794 - https://www.alldatasheet.es/datashee...ND/MP8794.html

I've tried injecting voltage to the output of the inductor and it looks that there's no short/leakage, it's consuming 1 amp and the ARM CPU in the board is getting some heat (around 35ºC) but in uniform way, not just a real hot spot like when a CPU is shorted.

Not sure how to continue from here apart from replacing burned components once I know which they are. What would you do now?

Thanks

[lotas]

If the discharge went through the HDMI port (if a receiver, satellite tuner, etc. was connected to it), you need to check the signal lines (there are 8 of them). What resistance do they have relative to ground and where do they go to, either to the main processor or to the HDMI hub? What voltage did you apply to the choke? It should probably be 0.9 - 1.2 V, which is the processor core voltage. If you applied more, the processor is likely dead, unless it was killed by lightning beforehand.

F2 - EDZTE616.8B (Zener Diode)

[lotas]

XR-xxA95K IC811 0.8V POWER GPU

[joliver82]

Thanks a lof for toour reply lotas

I'm 90% sure the dischage went through the HDMI port because he also gave me a PS5 pro which has the power supply fully burned and also the HDMI 0.9 regulator IC and the HDMI controller MN864739 were shorted/burned. This PS5 was connected to the TV at that time.



Resistances to GND from top to bottom (meassured from the left of the resistantors):

• 44 Ohm
• 9.5 Ohm
• 240 Ohm
• 647 Ohm
• 3.9 Ohm
• 6.7 Ohm
• 8.5 Ohm
• 42 Ohm

The HDMI ports are directly connected to the ARM CPU. Do the resistances meassured look correct?

I forgot to mention, in previous post... I injected just 0.8v. If I don't know which voltaje should have the line I never use anything over 1v just in case to avoid killing anything, so if I'm lucky the CPU could have survived to the lighting

Thanks for pointing me to the proper diode. Don't you know the model of the 3 pin "D·I€" marked component?

Thanks also for the image stating the expected voltaje in that line. Could you upload the whole file (or tell me where could I get it from) so I can check all expected voltajes in the board?

I've noticed something weird, when injecting in the right side of the inductor, some voltaje is leaked to the left side of MP8794, at VIN pins. I think this shouldn't be happening. Could the MP8794 be burned also?

[lotas]

There should not be any Ohms on the HDMI lines. Even on just one line (differential pair) there will be a short - the hub, HDMI controller is not working.

It turns out that the ARM processor got it, and lightning could have done anything. I think you'd be better off looking for a donor with a broken screen and replacing the motherboard.

Well, in the PS5, it's 99% likely that the motherboard is burned out, not just the power supply.

Was the PS5 connected to the internet via a LAN port?

[joliver82]

really? should be open line to GND for all HDMI lines? Bad news...

I've found replacement boards at ebay at 170-200€. Not so expensive for the cost of a new TV like this one, but wanted to try getting this board back to life

Not really, the PS5 doesn't look that burned, only HDMI related components, the APU looks good. I've not continued working on it because I cannot buy a replacement for Richtek RT6575K which is burned...

As far as I know the PS5 was not connected using ethernet. Does it make any difference?

[lotas]

The discharge usually passes through the LAN port, and then throughout the entire board, affecting HDMI, the south bridge, etc.