Panasonic TC-P65VT30 No Power, No LED

[pokepoke0610]

A friend of mine experienced a power surge that damaged his Panasonic Viera TC-P65VT30 Plasma Television. The symptoms are no signs of power and no blinking LED code nor is the LED lit. After taking off the back, I inspected the boards and performed the testing advised on pages 25-27 of the Service Guide for Panasonic Plasma TVs. In ohming out each of the pins on the SS, SC and A boards I didnt find a short circuit to GND. I made these
measurements unpowered with each connector disconnected from the power board. This seemed to indicate that I should replace the main power board.

I did inspect the power board (PDF and photos attached) which showed some damage. Feeling good I ordered a new main power board, plugged it in and experienced the same result. No change. No LED, no blinking, no clicking of either relay, nothing.

WIth the new power board installed, I measured the voltage of connector P6 on the main power board. All pin voltages were 0V except pin 6 which measured 5.06V. I am assuming this is the standby supply.

The voltages on connect P35 were all 0V. The voltages on pins 1 and 3 on "connector" P34 was 15.66V and 0V on pin 2.

I have inspected the A board with a magnifying glass and cant see any signs of damage (like on the power board), although that doesnt mean there isnt any but I didnt see anything obvious.

Any suggestions or ideas would be greatly appreciated as to what the next step(s) is. Thanks!

[diif]

Re: Panasonic TC-P65VT30 No Power, No LED

I see a bit of flux residue in photo 3 but no damage.
Did you check all the fuses on the power board ?
What about the other two power boards ?

[R_J]

Re: Panasonic TC-P65VT30 No Power, No LED

If you have STB+5V on P6(6) going to the main baord, and you don't have any voltage (or voltage change) on P6(1) PANEL_MAIN_ON when the power button is pressed, I would start checking the main board, I suspect that's where your problem is. Likely that pos PEAKS ic. But there are a number of 0Ω resistors off the STBY+5V line that should be checked, maybe one might be open. also check ic5000, looks like it supplies stb1.2v and stb3.3v

[Beau28713]

Re: Panasonic TC-P65VT30 No Power, No LED

Check your MosFets on the SC and SS boards for shorts across the Drain and source.

[pokepoke0610]

Re: Panasonic TC-P65VT30 No Power, No LED

Thanks for the responses.

diif: I checked all the fuses I could find on the power boards including a few surface mounts and all were fine. I will go back and look for the all the fuses called out in the
service manual again. I have checked the fuses on the PSUB board. I have also applied power to the 2 relays with the board removed and heard them click at around 8V (and hold at much lower voltage) so my guess is that board works.
R J: Am I correct that you are asking me to check pin 1 of P6 on the power board. Is a voltmeter going to register a significant enough change or does it require an oscilloscope (which I dont have)? I will try that.
Without a schematic (and any voltage labels on the board) it is a bit cumbersome to trace out the STBY+5V but will do my best. I will do my best to find ic5000 and find stb1.2v and stb3.3v.
Beau28713: Do you know specific mosfet instance numbers to check on the SC and SS boards?

[R_J]

Re: Panasonic TC-P65VT30 No Power, No LED

pin1 of P6 is the power supply on/off pin, it will change from 0 to 3.3 volts or 3.3 to 0 volts when the power button is pressed, IF the main board is working, but I suspect the main is bad
Look at post #2... a service manual. its not the best but it is better than nothing. There is no point checking the ss and sc boards if the main is not even turning on the power supply. (disconnect them from the power supply if you suspect them) If the main was working you should at least get the front led, flashing an error

[Beau28713]

Re: Panasonic TC-P65VT30 No Power, No LED

I agree with above post

[pokepoke0610]

Re: Panasonic TC-P65VT30 No Power, No LED

R_J: There was no change in the voltage of pin1 of P6 (it stayed at 0V) when the power button was pressed. I still need to find IC5000 (and STB1.2v and STB3.3v). Will try and get to that this weekend. It seems as though the main board is damaged and should be fixed/replaced, but am wondering what the likelihood of other boards being damaged is.

[pokepoke0610]

Re: Panasonic TC-P65VT30 No Power, No LED

I ended up buying a new main board and installed it with the original power boards. TV powered up and worked great!

One interesting note, I originally powered up the TV with the new main board through my dim bulb tester (with a 100W incandescent bulb) and the TV didnt power up at all (didnt hear any relays click). Only when I plugged it in directly to the wall did the TV work properly.

Thanks for the advice!

[R_J]

Re: Panasonic TC-P65VT30 No Power, No LED

The whole tv will draw too much current and too much voltage will be droped across the bulb for the tv to work, the lamp test is more for just testing the power supply by itself.