Panasonic TH-42PZ77U No Pwr, Blinking 7 Times

[marster]

I have a Panasonic TH-42PZ77U; I am experiencing the 7 blink power issue. I did the usual troubleshooting by trying a new outlet and unplugging all the cables from the plasma. Then I downloaded the tech manual and went through the troubleshooting steps. When I unplugged the SU board the TV powered up so I ordered an SU board. When I installed the new SU board the same thing is happening. Could the SC board be frying the SU board when I power it up? Your help would be very much appreciated.

[rayrod81]

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

The plasma panel is bad. When the SU or SD boards in this model go bad it is caused by a shorted electrode in the screen itself. It is not repairable.

[ben7]

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

A bad buffer board can take out a sustain board.

[rayrod81]

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

Panasonic has designed their plasma TVs so well that the buffers are isolated from the SC board and vice-versa. I have never seen a Panasonic with a bad buffer that was caused by a bad sustain or a sustain damaged by the buffers.

Anyway, the OP stated that the TV did not throw a blink code when powered on without the SU board attached confirming that the SC board is fully working.

[marster]

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

When I unplug the SU board and turn on the TV as the tech manual requested the screen turns on and I can see the menu. But I can only see the bottom half of the screen because the SU board is out. If the panel was bad would it power up and the screen turns on? As soon as I put the SU board back in the screen does not turn on and the power light flashes 7 times then pauses and repeats. If it is a buffer board how do I figure out which one?

[rayrod81]

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.

[marster]

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

So when I connected the new SU board it fried it when I powered it on correct?

[rayrod81]

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

Yes the screen fault immediately shorted the SU on power on. The rest of the boards are good including the SC and SD boards.

[marster]

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

Bummer, I searched the web for days before trying anything. You answered all my questions in a few minutes. Thanks for your help.

[cuclainne]

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.

Followed the service bulletin, looks like the SC board is the problem. I removed the board and would like to check the 5N2307 FETS. How do I do this?

[chiefk]

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

I have a 42P700U with the 7 blinks. I have gone thru the troubleshooting steps and now with the SU board disconnected it stays powered up. My question is can I hook the board back up and just disconnect the 4 ribbon cables that feed the display panel? I want to make sure it is not my panel that is bad. My thought is if the SU board is in fact defective it will still give me the 7 blinks with the panel disconnected.

[tom66]

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

If the panel really is defective the SU will have been damaged by the short and you should get 7 blinks but this also indicates an SU board failure so you have to take a chance.

[chiefk]

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

If the panel really is defective the SU will have been damaged by the short and you should get 7 blinks but this also indicates an SU board failure so you have to take a chance.

So what you are saying is I should change the SU and see what happens? Maybe waste alot of money. Can the SU be disconnected from the panel side and not damage it?

[chiefk]

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

After doing a visual inspection on the display panel I found a spot where the lines are broken. It looks like a small cross where there are no lines. What is this? Is this possibly a shorted panel? I am still waiting for my new SU board and I am afraid that if this is a short in the panel I am just going to fry the new board. I tried to take a picture of the defect but it is impossible due to the reflections. When I shine a light on the panel it is easily seen. I estimate the size as .09 wide by .06 up and down.

[freakaftr8]

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

That doesn't sound too good. Do a resistance check on the ribbon that goes to the buffer board where the defect is. Look for shorts to ground

[chiefk]

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

That doesn't sound too good. Do a resistance check on the ribbon that goes to the buffer board where the defect is. Look for shorts to ground

OK I checked from chassis ground to all the pins on the ribbon cables using my digital ohm meter. All checked open.

[chiefk]

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

Just received the new used SU board and installed it. Same problem. Disconnected board and set powers up normal and stays on. I guess I got a bad board or there is something really crazy. I even disconnected the 4 ribbon cables going to the display and it does the same thing, 7 flashes of death.

[tom66]

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?

[chiefk]

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

NO, but I will look for them. They are on the SU board?

[tom66]

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

On the SC.