Panasonic TH-50PZ80U 7 blink

[Caleb]

Hello everyone, trying to fix this plasma for a friend. 7 blink error, pulled the manual from one of Toms posts on this model. It indicates that 7 blinks is su,sd or sc. I think I have it isolated to the su board. the top three pins of the connector are shorted to the middle four pins. On the sd they are not shorted. I just would like confirmation that Im not missing something before I order a replacement. Thanks

[tom66]

Re: Panasonic TH-50PZ80U 7 blink

Have you tried buffer board isolation procedure?

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[Caleb]

Re: Panasonic TH-50PZ80U 7 blink

I tried to turn it on with the top one unhooked, but it is the newer version that wont come on if the buffers are disconnected- so it still gives 7 blinks. I looked over that manual but its not very clear what the strap is doing. Am I supposed to power it on with the strap in place? Sorry if Im being daft but, I havent had much luck with plasmas so far. I dont want to cause more trouble than I already have.

[tom66]

Re: Panasonic TH-50PZ80U 7 blink

Yes, what you're doing is jumpering the CHA signal so 7 blink error (buffer disconnect) won't occur. 7 blinks can still occur for other reasons though.

The jumper wire goes from CHA to the VF GND, which is the "HV DANGER" screw. The two flex connectors are unplugged on the SD, as well as the ribbon between SU and SD. You can leave just the top buffer connected.

[Caleb]

Re: Panasonic TH-50PZ80U 7 blink

Ok made up a jumper tried it with the su connected and sd disconnected with the exception of the jumper, still get 7 blinks. then tried it with both su and sd disconnected with jumper in place -still 7 blinks. Im not sure how the jumper provides feedback if everything is unhooked? Could you explain a bit more? I take it that means there is trouble in the sc as well as the su.

[tom66]

Re: Panasonic TH-50PZ80U 7 blink

The VF, produced by the SC board, needs to be fed thru the buffers to the CHA signal. CHA is on the flexible connectors that you unplug to isolate, so the jumper is essentially replacing the CHA signal which the buffers would normally complete, which not connecting anything else (the buffer board is attached by one "pin" only (the "VF"): it's like lifting a diode on one leg, it keeps it isolated.)

Note, SC failure can still cause 7 blinks. Typically this can be caused by Vad or Vscn voltage being bad. With SU/SD isolated, you should have a second or so to check Vad and Vscn.

Service manual:


shows Vad = -140V, Vscn = Vad+148V = 8V. Test points are on SC board. Vad below -120V will trigger 7 blinks. Not sure about Vscn.

[Caleb]

Re: Panasonic TH-50PZ80U 7 blink

Ok I will test out those voltages and reply back, Just to be sure though the su having shorts on those pins means its toast right?

Update: I tested at two points on the bottom of the sc board marked tpvad and tpvscn. The Vad is reading at -138.8v but Vscan only reading 4.8v.

[tom66]

Re: Panasonic TH-50PZ80U 7 blink

Probably, though it could have shorted because of bad voltages from SC. (Too high or reverse biased.)

[Caleb]

Re: Panasonic TH-50PZ80U 7 blink

Possible failed components to cause the low Vscn? Also without the sc plugged in it starts up without any blinks.

[tom66]

Re: Panasonic TH-50PZ80U 7 blink

Vscn is fine, should measure around 8V but to be honest 5V is fine, it is +148V more than Vad which is -140V so it should be 8V. To verify this you can try dropping Vad and Vscn should increase.

[Caleb]

Re: Panasonic TH-50PZ80U 7 blink

Ok I moved Vad up to -136 and Vsc is now at 7.76. Still 7 blinks. What to test next?

[tom66]

Re: Panasonic TH-50PZ80U 7 blink

Probably only buffer fault then.

[Caleb]

Re: Panasonic TH-50PZ80U 7 blink

Shouldn't the bypass give the sc a clean bill of health? or does it do 7 blinks no matter what as long as it isn't connected through? (this is a 2008 model)

[tom66]

Re: Panasonic TH-50PZ80U 7 blink

Some other things to check before buffer swapped to rule in/out SC:

• Capacitor C725 on SC board, near C723 and IC724 and D1671: voltage across should measure around 5V.
• Capacitor C724 voltage across around 5V.
• Capacitor C723 voltage across around 15V.
• Capacitor C721 voltage across around 15V (Big electrolytic 100uF/50V.)
• Ends of diode D721: 16V one end, 15V other end, negative lead on negative of C721.
• Ends of R480: both ends should measure 5V, negative on chassis.
• Elsewhere, diode D820 pins should measure around 0V on all, negative on chassis.
• Diode D718 near VSET circuit: both ends 0V, negative on chassis.
• VSET test point not more than 395V, negative on chassis.

[Caleb]

Re: Panasonic TH-50PZ80U 7 blink

Ok tested out those I could find
C721 15v only appears for a second
C723 0v
C724 0v
C725 0v
D721 0v both ends
D718 0v both ends
I found the designation for 820 but am not sure where it is on the board
R480 0v both ends
Vset got a 405v momentary reading on the multimeter but then goes to 350v. didnt see the momentary high on the scope so I think its just the multimeter settling.
As for why I only have voltage on the cap, I think the board is shutting off before I can get the probes on the test points as I couldn't get a good reading off the electrolytic until i hooked it up on the scope, then it briefly came up to 15v.
Adding in a pic of the locations of the test points as I had some trouble locating them. Hopefully it will help out the next guy. Spent an hour cleaning the board of smoke residue so I could read all the designations. Cant imagine why anyone would want that crap in their lungs.

[tom66]

Re: Panasonic TH-50PZ80U 7 blink

OK, was that with the buffer board removed? It looks like you have a bad SC board too...
My 42" PZ80 was full of cigarette smoke... it stank when I first got it powered up because all that crap came out the fans... jeez if that's inside the TV what's inside your lungs?

[Caleb]

Re: Panasonic TH-50PZ80U 7 blink

Will it kill my new buffer if I hook it up to the bad sc? And how difficult is it to repair the sc? From my online research it looks like its better to replace buffers. But there are mostly repaired sc boards availible. I did have the buffers unhooked but the jumper still In place. Is there a thread with a test repair sequence on an sc? Most common failure points?

It is difficult to get the probes in place quickly do its possible the voltages that are supposed to be there are disappearing before I can meter them. Or are they supposed to remain steady with the jumper in place?

I have to say this is the dirtiest TV I've ever seen and it not just dust its gooey sticky guck that goo be gone had a tough time removing. If I can get some new parts I will spend some time cleaning out the guts.

[tom66]

Re: Panasonic TH-50PZ80U 7 blink

It is rare for the SC board to kill the buffers, though it does happen on some newer Panasonic sets I believe. It's not typical for this set but I wouldn't want to risk it.

Unfortunately due to the error detect, you will need to take the measurements while the set is briefly powered on, before it goes to 7 blinks. This does mean turning it on and off a lot. I expect the voltages to disappear because it is detecting a fault and shutting down. Panasonic sets have tons of error detect circuits unlike Samsung and LG; on a Samsung or LG, the appropriate components will typically go "bang" and it might take a few transistors with it, a Panasonic will typically have the same but usually more components survive. This can be both a blessing, and a curse, because tracking down the exact cause of the general "7 blinks" fault is difficult. 6 blinks is a lot easier and only really caused by an ERC malfunction.

[Caleb]

Re: Panasonic TH-50PZ80U 7 blink

Alright, I had my son power the tv on and off with my probes in place, and still no voltages present on that series of caps, I dont suppose there is a schematic floating around anywhere?

Shop Jimmy doesnt have any in stock, there are two on ebay but both were pulled from cracked screen tvs. From what Ive read so far the simple act of cracking a plasma when its on commonly takes out the buffers and sometimes the y-sustain. How likely is this on a panasonic of this generation.

[tom66]

Re: Panasonic TH-50PZ80U 7 blink

Yes, I've been working out the voltages from the schematic. This is 42" but board layout is the same, just more transistors and caps for bigger panel.


Dead buffers due to cracked screen is quite possible, I'm afraid. You can try to test them to rule out boards you buy:
http://www.youtube.com/watch?v=51SZsfH60EY

SC boards I'm fairly sure don't die due to cracked screens... but you have to take into account the angry guy smashing his 6/7-blink telly, putting it on the curb and being collected by one of these parts guys... I figure that's how most of these dodgy parts get on eBay.