How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Louie Your Own Question
Louie
Louie, Technician
Category: TV
Satisfied Customers: 11447
Experience:  25+ yrs. experience in the field and 5+ yrs. online, down to component level.
13948492
Type Your TV Question Here...
Louie is online now
A new question is answered every 9 seconds

I have a panasonic th-42PZ80U with the 7 blinking light problem. I have read that there i

Customer Question

I have a panasonic th-42PZ80U with the 7 blinking light problem. I have read that there is a fairly simple debug process to figure out which board is bad, and maybe, if I'm lucky, determine which component(s) are fried. I thought I had the 46", but I just looked and my TV is a 42". I'm trying to put together my diagnostic plan, and here I am...
My goal is to spend some time trying to fix it, if it seems that I'm likely to succeed. Otherwise, I'll just get another set.
Submitted: 1 year ago.
Category: TV
Expert:  Louie replied 1 year ago.
Hi and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, this model uses the GPF11DU Chassis where 7 blinks indicate a fault in any of 3 boards. Please click HERE.Proposed preliminary try would be to check for any loose connectors and/or burned parts from the boards. Then try disconnecting the SU board and determine if the TV would at least power up and/or operate albeit with a different fault/symptom.Please post back results / observations of the above once tried.Replacement boards may be inquired from HERE (among others). Replacing the SU board would serve as both an attempt ofd a fix and as a test by process of elimination.
Customer: replied 1 year ago.
Well, I could just try replacing the SU board, but I did some more detective work. First, I obtained the service manual for this TV. The diagnostic flow chart on page 15 (attached) indicates that, for no picture, check the status of the LEDs on the SC and SS boards. Both LEDs light up... so that means the D board is suspect.I also did some disconnecting of individual boards. First the SU ... no change to the 7 blinking light behavior. Then also disconnected the SD... same result. Then disconnected the SC board as well: now the TV stays on, but of course there is no picture. I reconnected everything but the ribbon cable between the D board and the SC board (SC20 - D20) and the TV stays on, with a solid red light (but of course, still no picture).
So... because the SC LED lights up (indicating the SC board is OK) and disconnecting the ribbon cable to the D board prevents the TV from going back into standby, don't you think that the problem looks like the D board?I'm tempted to just buy a D board, and try replacing it. It is a pain to get to it (the A board needs to come out, and there are a bunch of cables to disconnect, etc.) but it seems like the best guess. Your opinion?
Expert:  Louie replied 1 year ago.
Based on these test, then yes; the primary suspect would have shifted to the D board. However, there is also a (remote) possibility that the panel itself is causing the D board (and/or the other boards) to fail.But then again as the boards interact, then neither the blink code nor the disconnecting would be 100% fool proof diagnostic.Which then leads us back to board replacing as an attempt of a fix and as a test by process of elimination.The only caution would be to order/get an identically numbered board as there are several versions for the same model.
Customer: replied 1 year ago.
Thanks for the heads up about the various numbered boards. I guess I need to take it apart enough to see the part number on the PCB. I was going to just order one, but now I'll access the D board first. My plan is to find that number, order a replacement, install it and try. I'll let you know how that turns out. Thanks for now.
Expert:  Louie replied 1 year ago.
The D board would be numbered with something like TNPA4439BLS. The suffix in bold BL is also important. Appreciate the post back and an update when able.
Customer: replied 1 year ago.
Well, it has been a long time. I bought the correct D board and replaced it a while ago. Everything seemed to go well, but after i was done the problem had not been resolved, and the symptoms were identical. I suppose that your earlier suggestions are still appropriate, but I've decided to give up on trying to fix it myself, because it seems like it could be one of a number of failures, with no way for me to diagnose the problem by measuring signals at test points without better documentation.
So I'm willing to close the case, and recommend you, but my remaining question is: what should I do with the old TV? Is it useful to someone for parts, or is it best to give it to an electronics recycler?
Thanks,
Peter
Expert:  Louie replied 1 year ago.

Appreciate the update Peter and sorry to hear the lack of development.

 

Perhaps the information HERE may shed additional insight / options.