PANASONIC TX-P42X10Y Plasma TV damaged after a power spike

[tofik]

Hello, I have an PANASONIC TX-P42X10Y Plasma TV, purchased new in 2009.
Unfortunately plasma is not working at all after a power spike. Standby LED is not even working.

I did some quick tests, YSUS + ZSUS MOSFETS and IGBT's are free from shorts, diodes on these modules seems to also be fine, buffer board is free from shorts as well.

Anyway I focused mainly on the PSU, did some voltage tests with the results as below, I attached them on the photo (also please see attached PDF with the SERVICE MANUAL for this model, page number 43).

I understand that to test the Vsus + Vda voltages, I would need to manually force the PSU with 1k resistors between ST-BY5V - STBY-ON pins plus ST-BY5V - PANEL-MAIN ON pins and with some high power bulb across Vsus and GND, right?
I didn't try this yet as I am afraid that +15V voltage which I tested before, seems to be the culprit here, I am just not sure about it 100%

On the PSU, I already tested: all diodes, all transistors, bridge rectifier, all fuses (7 in total!), capacitors (capacitance test + for shorts), varistors, high power resistors, both relays and obviously visually checked everything very closely and everything what I mentioned, seems to be fine, PSU is producing +5V correctly and now I am just not sure about this +15V voltage, could the mainboard control it, same like the Vsus + Vda voltages?

Thanks everybody for reading.

[nomoresonys]

Re: PANASONIC TX-P42X10Y Plasma TV damaged after a power spike

dead as can be, you do have voltage where the power cord plugs into tv correct?

[tofik]

Re: PANASONIC TX-P42X10Y Plasma TV damaged after a power spike

Thanks for your message.
Yes of course I have it, 230V AC on the input (I am in Europe).

So you think PSU is dead? It produces +5V and I also checked most of the components on the pcb.
If that +15V is the problem here, where should I be looking on the board to find a culprit? I will check schematic tomorrow but if there is anything obvious, I would be very grateful for any advice

[nomoresonys]

Re: PANASONIC TX-P42X10Y Plasma TV damaged after a power spike

does that mean all tests done with mainboard disconnected, mainboard is what tells it to turn on, so like you have there you will only get the standby voltage with it disconnected.

[tofik]

Re: PANASONIC TX-P42X10Y Plasma TV damaged after a power spike

I did two tests:
- one with mainboard connected to power supply, +15V is 0.29V
- second test with mainboard disconnected from the power supply, +15V is 0.8V

Isn't this +15V a supply for a mainboard?

[nomoresonys]

Re: PANASONIC TX-P42X10Y Plasma TV damaged after a power spike

did you notice the green sos led on one of the boards blinking?

[lotas]

Re: PANASONIC TX-P42X10Y Plasma TV damaged after a power spike

I did two tests:
- one with mainboard connected to power supply, +15V is 0.29V
- second test with mainboard disconnected from the power supply, +15V is 0.8V

Isn't this +15V a supply for a mainboard?

Why does the motherboard need 15v in standby mode, the motherboard should always receive 5v, and the motherboard puts the power supply into operating mode and then these 15v go to the motherboard and other boards.

[Biruslapio]

Re: PANASONIC TX-P42X10Y Plasma TV damaged after a power spike

15V, VS and Vda only comes on when panel_main_on is HIGH, if it's not going it's the logic board or main board.

[tofik]

Re: PANASONIC TX-P42X10Y Plasma TV damaged after a power spike

did you notice the green sos led on one of the boards blinking?

I checked it very precisely and no LED lights up at all, complete darkness on all boards.

Why does the motherboard need 15v in standby mode, the motherboard should always receive 5v, and the motherboard puts the power supply into operating mode and then these 15v go to the motherboard and other boards.

15V, VS and Vda only comes on when panel_main_on is HIGH, if it's not going it's the logic board or main board.

Okay so I understand these voltages in standby mode are fine for +15Vs. Seems like the PSU if fine and probably the problem is the mainboard.

Just to confirm that, how exactly force the PSU to test 15V, VS and Vda voltages?
I found procedure on the forum for Panasonic TC-P60ST60 Plasma model which says:
Connect two (2) 120Vac 60W light bulbs in series and make attest light.
Disconnect all connectors from the PSU to the other boards.
On the P6 connector, connect a 1k resistor across the st-by5V pin and the stby-ON pin.
Connect another 1k resistor across st-by5V pin and the F-stby ON pin.
Connect another 1k resistor across st-by5V pin and the panel-main ON pin.
On the P2 connector, connect your test light across the Vsus pin and GND.
Plug the PSU into the ac.

If the test light glow bright and remain ON, measure Vda across P35 Vda pin and GND.
Measure the M5V, 17V and 12V and see if they are all there.
BE CAREFUL and not short out any connections and beware of an electric shock hazard.
If the PSU is good the test light will remain On and all your voltages are present it would be safe to say PSU is good. Would it be the same for my PSU?

BTW. Is there any way to run a pattern test without a mainboard? I know it's possible for LG plasmas, any chance to run it on Panasonic? It would allow me to test PSU + YSUS + ZSUS and buffer boards.

I think the problem will be the main board, the model number is TNPH0783. I haven't found any to buy in my country, would any other model possibly be compatible as a replacement?

[Biruslapio]

Re: PANASONIC TX-P42X10Y Plasma TV damaged after a power spike

disconnect the PANEL_MAIN_ON wire from A-board to psu and feed 3.3V into PANEL_MAIN_ON on PSU.

If that works your psu will have 15V, Vsus and Vda will work, but disconnect the sus-boards and vda in case of the main board sending a bad signal to them.

The main board processor or HDMI chip is probably shorted or very damaged, I say the psu is totally fine since it didn't blow the fuse.