Panasonic TH-42PZ77U No Pwr, Blinking 7 Times

[chiefk]

Re: Panasonic TH-42PZ77U No Pwr, Blinking 7 Times

I can't find any transistors with that number. I have the Pan service manual and it does not list any 2N transistors. What exactly do they do? With the SC board connected and the SU board disconnected the set powers up good. Of course the upper screen is missing.

[chiefk]

Re: Panasonic TH-42PZ77U No Pwr, Blinking 7 Times

Do you think I fried the board when I plugged it into what may be a bad or shorted display? I just corresponded with the seller and he assures me that this board came out of a functional TV.

[tom66]

Re: Panasonic TH-42PZ77U No Pwr, Blinking 7 Times

It does sound like your panel is bad.

Though the board will have been removed from a TV with a cracked panel in 90% of cases. Most sellers do not test the TVs they tear down for parts.

[chiefk]

Re: Panasonic TH-42PZ77U No Pwr, Blinking 7 Times

It does sound like your panel is bad.

Though the board will have been removed from a TV with a cracked panel in 90% of cases. Most sellers do not test the TVs they tear down for parts.

I did ask him specifically if it came out of a cracked screen tv and he said no that it was working. Tom, what do you think the chances are of my display being bad? 100%? Do you think I fried the replacement SU board? Do you know of any way to test the display other than power on?

[tom66]

Re: Panasonic TH-42PZ77U No Pwr, Blinking 7 Times

Test both your SU boards with this method.

https://www.youtube.com/watch?v=51SZsfH60EY

Use "caution high voltage" screw point for one probe, and the ribbon connectors for the other.

If you have shorts on the same chip/ribbon, there's a good chance the panel is bad, but if the chips are different, I would doubt it.

[chiefk]

Re: Panasonic TH-42PZ77U No Pwr, Blinking 7 Times

My board is a TNPA4383 and it does not have the high voltage screw. So I checked it from pins A1 of the input to all the pins on the ribbon connectors. all open. Then I checked from B40 input to all the pins on the other ribbon connector. Everything was open except for A1 on the ribbon for SU13. It was 18 ohms on one board and 8 ohms on the other. The schematic in the service manual is for a different number su board but it looks almost the same.

[chiefk]

Re: Panasonic TH-42PZ77U No Pwr, Blinking 7 Times

The schematic in the service manual is for a different number su board but it looks almost the same.

Found the right schematic in a different service manual, the one for for PZ70. It looks like this pin with the low resistance goes to the Out1 pin on the IC. Tracing this back it looks like this is the pin that feeds the line that is broken or has a defect in the display. I guess I write off this TV as having a bad display panel. What a shame, just a bit over 5 years old on a $1000.00 tv.

PS: Found several pins coming from the same IC that are very low resistance.

[ruggb]

Re: Panasonic TH-42PZ77U No Pwr, Blinking 7 Times

There are some 2N5307 or 2N3995 transistors on your board. Have you checked those for shorts?

got the #s transposed
5N2307

[Lemieux]

Re: Panasonic TH-42PZ77U No Pwr, Blinking 7 Times

Here is a service bulletin on these models. The SU is the buffer board that I was referring to. When the SU or SD boards go bad then you must replace the plasma panel as well as the culprit board (SU or SD). So unfortunately the TV is not economically repairable.

Thanks for the pdf! Dosen't seem to work for me ;(

Panasonic 42" plasma tv, model TH-42PZ700U. The TV Turn On automatically when connected. Seven blinking led lights, no picture or sound. when I do a reset, (by holding the Power button 10 seconds) snow appears on the right side of the screen for a split second, then nothing... I unplugged the power cord then disconnect the SU and SD boards from the TV. With them removed, I turned the TV on (by plugging in, turn On automatically) and still see the 7 blinks code. With the SU board and the SD board still disconnected, I removed connectors SC2 and SC20 from the SC board. I plug in the TV and turn it on (with the power button). No error code this time. (no blinking, fans running). So I bought used SC board on eBay. After replacing the board, I still have the 7 blinks error code!!! Any ideas? Perhaps I bought a defective board (bad luck)...

[bretts]

Re: Panasonic TH-42PZ77U No Pwr, Blinking 7 Times

Thanks for the pdf! Dosen't seem to work for me ;(

Panasonic 42" plasma tv, model TH-42PZ700U. The TV Turn On automatically when connected. Seven blinking led lights, no picture or sound. when I do a reset, (by holding the Power button 10 seconds) snow appears on the right side of the screen for a split second, then nothing... I unplugged the power cord then disconnect the SU and SD boards from the TV. With them removed, I turned the TV on (by plugging in, turn On automatically) and still see the 7 blinks code. With the SU board and the SD board still disconnected, I removed connectors SC2 and SC20 from the SC board. I plug in the TV and turn it on (with the power button). No error code this time. (no blinking, fans running). So I bought used SC board on eBay. After replacing the board, I still have the 7 blinks error code!!! Any ideas? Perhaps I bought a defective board (bad luck)...

Did you ever figure out the issue with your 700U. I too have replaced SC, SU, and SD.

[ruggb]

Re: Panasonic TH-42PZ77U No Pwr, Blinking 7 Times

I have a problem child. It died with 7 blinks. I replaced all the mosfets in the long row - only 1 was shorted.
It ran for several months of very intermittent use then died again, same 7 blinks. This time i just replaced one shorted fet.
It ran for a few hours and died again. THIS TIME however, it keeps coming back to life and I can find no shorts.
I unplug, wait, replug and it is working sometimes or not. The last time I disconnected the power plug from the SC bd, I get the blinks, I reconnected it with a few sparks because the caps were still charged because of no load and it is working for 45 min now. Only worked for less than a min between unplugs b4.
Screen looks perfect. Maybe a bad signal connection??? I haven't replugged that yet. Any other ideas??

[dskall]

Re: Panasonic TH-42PZ77U No Pwr, Blinking 7 Times

One suggestion. NEVER plug/unplug connectors on plasmas until voltages are discharged or while powered on.