Panasonic TH-42PZ80B - Completely dead again

[tom66]

I had this nice 42 inch 1080p Panasonic plasma working in my bedroom for 5 months (it was the one with the cold joint on the power board.)

I decided 42 inch plasma is way too big for me so I got a 32 inch 1080p Sharp Aquos cheap for fixing up and sold this one, but a day later it came back with the original fault (talk about bad luck!) So I gave the guy his money back...

I've since traced it down to the AC detect board, which tells the PSU if the AC is present. I've found that when I freeze spray it, the TV will power up and work fine. Once it warms up, it only powers up intermittently.

I believe it's one of the ceramic caps on the AC detect board, but I can't be sure because the only schematic I have of it is the one I've reverse engineered (see below.)

https://www.badcaps.net/forum/attach...8&d=1367795705

I drew the PNP Q3 backwards in that by mistake. The emitter faces BIAS-9V and the collector is the output. C3 is the suspect. It's the biggest cap on the board by far, and it appears to be the only one where if it failed leaky, it would cause Q3 to stay off. It would have to fail very leaky (probably shorted.) But I cannot know it's value unless anyone else can measure it.

If I can't fix this part, I may have to think of an alternative AC detect circuit design... ideas coming soon.

[Blanqui]

Re: Panasonic TH-42PZ80B - Completely dead again

Hi tom.
This looks like you have to do a mod to this one.
There is a daughterboard on the powerboard. There you will find an IC which is a TEA1611T. You have to remove the 1uF cap that's between pins 11 and 13 from that IC.
Hope that helps!

[tw2005]

Re: Panasonic TH-42PZ80B - Completely dead again

Which board is the AC detect board Tom?

[tom66]

Re: Panasonic TH-42PZ80B - Completely dead again

Hi tom.
This looks like you have to do a mod to this one.
There is a daughterboard on the powerboard. There you will find an IC which is a TEA1611T. You have to remove the 1uF cap that's between pins 11 and 13 from that IC.
Hope that helps!

Unfortunately that's not the issue with this model, that would be too easy! Though the cause seems to be the same (leaky ceramic cap.) My set does NOT have a 10 blink or 2 blink code. It is completely dead. No power LED, no relay clicks, until you give a freeze blast to the AC DETECT board (which is an MC MODULE but it's not the TEA1611T boards.) Then it fires up and works perfectly until it warms up and the AC detect signal goes awry, causing it to intermittently shut down and restart as if the power cord were loose.

[tom66]

Re: Panasonic TH-42PZ80B - Completely dead again

Which board is the AC detect board Tom?

Will check when I open it up but it's one of the few that crosses the PRI-SEC boundary. Has two optos on it.

[Blanqui]

Re: Panasonic TH-42PZ80B - Completely dead again

Sorry, tom66. But don't you have MC201 on this TV set?
It's writren on my notes...
How weird!

[tom66]

Re: Panasonic TH-42PZ80B - Completely dead again

Sorry, tom66. But don't you have MC201 on this TV set?
It's writren on my notes...
How weird!

Yes, I do. But amazingly, both of my PZ8 series plasma repairs have not involved either MC201s. I got one with a loose LVDS which is still looking good in my lounge and playing fine after 6 months. And this one with AC detect issue. I have a friend who's fixed two PZ8 series with MC201 issues.

[tw2005]

Re: Panasonic TH-42PZ80B - Completely dead again

Ok, so we're talking one of those module boards that they give no info on in the standard schematic for the PSU. I've got the 46" PSU I'm yet to do for the 2/10 blinks on, probably similar PSU but I have no capacitance meter. Would have to pullit out and track down a meter at work to measure it next week if you're really stuck.

[tom66]

Re: Panasonic TH-42PZ80B - Completely dead again

I appreciate it. I've got an idea though involving using an 230V AC coil relay. I'm going to take 230VAC from the input and connect it to the relay, lift the opto and wire the relay's NO switch terminals to it.

I need to find a good AC relay with a sub 16ms release time. (~1 cycle AC.)

I'd like to do a proper repair though just replacing that capacitor, so I'll have to see if I can narrow down the fault any further.

[Blanqui]

Re: Panasonic TH-42PZ80B - Completely dead again

The capacitor doesn't have to be replaced, it has to be removed.
This is the repair suggested by Panasonic, I'm an ASC. I mean that this is the proper repair, LOL.
Anyway, maybe I got a little lost in translation. From your last post I haven't understood if you were saying you had or not that board.
Sorry for my English!!!!! :p

[tw2005]

Re: Panasonic TH-42PZ80B - Completely dead again

This board?
how critical would the value of the cap be do you think? Would it be worthwhile just finding a ceramic physically the same size from a scrap board?

Worst thing that could happen is it still does not work, surely?

[tom66]

Re: Panasonic TH-42PZ80B - Completely dead again

The capacitor doesn't have to be replaced, it has to be removed.
This is the repair suggested by Panasonic, I'm an ASC. I mean that this is the proper repair, LOL.
Anyway, maybe I got a little lost in translation. From your last post I haven't understood if you were saying you had or not that board.
Sorry for my English!!!!! :p

Yeah, I know about the MC201/MC301 repair but that's not the case with this TV. Since you're an ASC, could you look into whether my particular issue with the AC detect is also documented? (symptom: no power LED, TV acts DEAD, fuse is NOT blown) Maybe it gives the value of the cap.

Your English is fine, better than many natives of this country. I cannot speak Spanish at all so no need to apologise!

[tom66]

Re: Panasonic TH-42PZ80B - Completely dead again

This board?
how critical would the value of the cap be do you think? Would it be worthwhile just finding a ceramic physically the same size from a scrap board?

Worst thing that could happen is it still does not work, surely?

Yes, that one. MC501...

It's much worse unfortunately.

If the AC powers off and the TV keeps the VDA high while the 5V collapses, the panel goes BANG. And you get a dead driver chip and a dead panel. (Secondary breakdown due to overstress of IC, reverse biasing the diode between 75V and 5V in the IC substrate.) There is something like 3000uF of Vda capacitance (@75V) and only 1500uF of 5V capacitance so it's possible that the Vda will hold out while the 5V collapses. (I believe there's a discharge circuit which detects if AC turns off and dumps the Vda energy quick.)

It is documented in many PDP datasheets, I did not realise it until recently, but it's very important for the power voltages to be sequenced exactly, they specify it on the voltage page. If not, the panel can be damaged. I remember doing AC detect bridge on LG 42" plasma and others have done it on 50" plasma. Those seem OK, I tried that TV hundreds of times with no issue, but they did not engineer them as overkill-ish as Panasonic with only about 500uF of capacitance on Vda and 7500uF+ on 5V. So I could get away with it on the LGs, but I do not know if I can do so on a Panny and I don't fancy finding out...

[tw2005]

Re: Panasonic TH-42PZ80B - Completely dead again

The capacitor doesn't have to be replaced, it has to be removed.
This is the repair suggested by Panasonic, I'm an ASC. I mean that this is the proper repair, LOL.
Anyway, maybe I got a little lost in translation. From your last post I haven't understood if you were saying you had or not that board.
Sorry for my English!!!!! :p

Don't mean to hijack but,

Are you talking about the MC201/301 modules or the module Tom's working on?

I'd be interested on any info on the MC201/301 modules if all it needs is a cap removed, save me taking the module out.

are there any service bulletins you can share?

[tw2005]

Re: Panasonic TH-42PZ80B - Completely dead again

Yes, that one. MC501...

It's much worse unfortunately.

If the AC powers off and the TV keeps the VDA high while the 5V collapses, the panel goes BANG. And you get a dead driver chip and a dead panel. (Secondary breakdown due to overstress of IC, reverse biasing the diode between 75V and 5V in the IC substrate.) There is something like 3000uF of Vda capacitance (@75V) and only 1500uF of 5V capacitance so it's possible that the Vda will hold out while the 5V collapses. (I believe there's a discharge circuit which detects if AC turns off and dumps the Vda energy quick.)

It is documented in many PDP datasheets, I did not realise it until recently, but it's very important for the power voltages to be sequenced exactly, they specify it on the voltage page. If not, the panel can be damaged. I remember doing AC detect bridge on LG 42" plasma and others have done it on 50" plasma. Those seem OK, I tried that TV hundreds of times with no issue, but they did not engineer them as overkill-ish as Panasonic with only about 500uF of capacitance on Vda and 7500uF+ on 5V. So I could get away with it on the LGs, but I do not know if I can do so on a Panny and I don't fancy finding out...

Ok, that's beyond me but good to see someone thought about it. LOL

[tom66]

Re: Panasonic TH-42PZ80B - Completely dead again

The other issue I haven't considered is it might do a 2, 4 or 10 blink code when AC power is removed while running, not sure if AC relay will cause this or not. All a matter of getting timing right.

[tw2005]

Re: Panasonic TH-42PZ80B - Completely dead again

Well that module MC501 MDPTZA101 is found on 42, 46 & 50" models, I guess you don't have another PZ series laying around?

[tom66]

Re: Panasonic TH-42PZ80B - Completely dead again

I do, 46". I'm leaving taking apart that as a last resort because it's used every day at the moment. The 42" can wait for now.

Though I may be getting a 50" 2011 Panny Pro 3D 1080p plasma monitor soon to play with, if the auction comes thru... that ought to be fun... supposed to be the equivalent of the TH-P50UT30 but with only HDMI and DVI... faulty though... If I put that on the wall I'll tear the 46" open.

[tw2005]

Re: Panasonic TH-42PZ80B - Completely dead again

That module looks like it's available $40-50 in the US, not as much fun or cheap as a single component repair.

I thought you had a 46" too, I thought my memory was going there for a moment.

Yes i understand how painful it is pulling the back off and getting the PSU out , probably why I have not gone back into mine again. Interesting that the MC201/301 only needs that cap removed.

Could have saved $25 on 2 TEA1611 ic and the tiny caps. I might just give it a go removing that cap first because I did get it going again just reflowing it but it has failed good and proper now.

is'nt the UT30 series the generation that quite a few are having the SC boards go like the poor chap in the states that had his repaired under wty only to have the same fault 6 months later and be left high and dry out of wty?

[Blanqui]

Re: Panasonic TH-42PZ80B - Completely dead again

Hello, tw2005.

I thought tom66 was suffering from the MC201 module but it seems it's not the problem.
In any case, the problem this module suffers from is the cap between legs 11 and 13 of IC TEA1611T.

Referring to your request, tom66, there is no mention to what you say. The closest thing is to replace MIP3A and the fuse on the standby power supply. But I guess your fuse is right and don't need to replace MIP3A.