Panasonic TH-42PX25 Digital HD Plasma dead

[Quasar]

Re: Panasonic TH-42PX25 Digital HD Plasma dead

Pic of current condition:

[PlainBill]

Re: Panasonic TH-42PX25 Digital HD Plasma dead

Thank you for the reply and analysis.

Power has been restored, Cap'n!

Details and photos to follow.

Teaser: Problem was in the 30v line to DG that goes to H that ends up in TB.

------------------------------------------------------------------
New set of troubles:

With no input and with cable input:
- No picture
- Horizontal purple and green lines/bars
- OSD is clear and perfect
- Split screen functions but same lines/bars
- PIP functions but is B&W, not a complete picture, and grainy. It moves to the 4 corners when directed.
- Sound is good

Q

I await your revelation with bated breath.

PlainBill

[Quasar]

Re: Panasonic TH-42PX25 Digital HD Plasma dead

I kept being puzzled by the drop in resistance when the PA2 was connected. With the meter set to chime mode for low ohms, I started plugging PA2 in on an angle to see if I could narrow what pins it was shorting on. I noticed it was at the low numbered end and set out to test those pins.

I used 1 strand of a multi-strand wire to probe the plug (like threading a very fine needle) and the other end of the wire to the socket. I figured I should have no more than 10 pins to test from this 40 pin connector. To make it even easier, one whole side of the connector pins are grounded, so this going to go more quickly than expected.

The first pin was the one which made the meter chime. I tested 2 more to be sure, but no others caused the chime. I had found the clue to the problem.

This is the (only) white wire in the connector. All others are blue. It is the BT30v supply generated by IC7581 on PA. I still have not figured out how it was causing the low ohms reading. That chip is not energized until -switched- 9v is applied, and the switched 9v line is open past Q7501 until the power switch is pressed...? I just don't see the connection? (no pun intended).

Followed the trace once it left the connector on DG. Found the problem within a minute. (good lighting and a pair of reading glasses)

A chip L-C appeared cooked as the pics show. I continued following the trace to the interconnect to H. Across the H board to the TB module connector. Opened the TB up and followed it inside to a 563 (56k) chip resistor. With that value I determined that the chip L-C must have failed by itself and was not from an overload in the circuit beyond it. Max current draw with 56k is <0.5mA.

Not having one of the chips handy (can't even identify it from the Panasonic number and it's not called out on the parts list), I decided to improvise. I found an old scrap board about and removed a 1mm, 0 ohm shunt from it and installed it on the DG.

Back together an plugged in, I had 9.3 volts on the 9v line. Switch on and away she went!

Now to solve the current issue of the horizontal lines...

Q

[Quasar]

Re: Panasonic TH-42PX25 Digital HD Plasma dead

PlainBill,

From what I have read, I'm afraid this is a bad DG board after all. I am not certain as there is no specific picture like this. If it is a bad DG, the cheapest I have found is about $250, with some prices as high as $850. I might go the $250, but only if I can be certain that that will correct the problems and no other boards will be required.

I know this was a $1200 set 6 years ago, and I do like Panasonic products, but saving for a new set may be a better idea.

From your statement, I have requested Wizard to come look at the thread and give his opinion.

Thanks again for your time.

Q

[PlainBill]

Re: Panasonic TH-42PX25 Digital HD Plasma dead

PlainBill,

From what I have read, I'm afraid this is a bad DG board after all. I am not certain as there is no specific picture like this. If it is a bad DG, the cheapest I have found is about $250, with some prices as high as $850. I might go the $250, but only if I can be certain that that will correct the problems and no other boards will be required.

I know this was a $1200 set 6 years ago, and I do like Panasonic products, but saving for a new set may be a better idea.

From your statement, I have requested Wizard to come look at the thread and give his opinion.

Thanks again for your time.

Q

I have a few more suggestions. Clearly, spending $850 makes no sense. Currently Fry's Electronics has several new 42" 1080P plasma TVs for less than that. Saving electronics from the landfill is a GOOD thing, but let's not be ridiculous.

First, Tri State Modules has the module for $145 + shipping. I've never done business with them, so the usual disclaimers apply.

Second, I don't know if this panel had this feature, but on some models of Samsung it was possible to put the plasma panel into 'white screen mode' by setting switches on the Main Control board; the board that receives the LVDS signal from the main signal board. Panasonic refers to these as the D and DG board respectively. IF Panasonic has that feature, it will be easy to establish that the DG board is at fault.

PlainBill

[Quasar]

Re: Panasonic TH-42PX25 Digital HD Plasma dead

PlainBill,

Proving the DG failure and being able to test for it is a method that is not explained in the "Plasma Training" pdf's I've grabbed so far. The farthest back they have is 9th gen., and this one is 7th or 8th (2004-05). I am unsure as I can't confirm which. None of the ones shown in the training files have all these boards. !!

Panasonic's schematics on the DG basically say "Not field serviceable - Replace Module". It would be darn difficult too get to test points too, as the DT board sits atop it and is plugged into it directly.

I did see somewhere on AVS forums the "white screen" test. I'll find it again and see if I can figure out if this one can do it too. I registered so perhaps a post there will elicit a response from the 2 techs that respond to a lot of questions.

I did perform the "reset" function on the set, but no luck. (OK & Power pressed together) It brought up the "first use" menu and scanned channels but nothing different afterwards.

Another note I did see was a tech on another forum answering a question for someone with the same set. His reply was the DG board had failed and that these sets had problems with said board.

I just was at HHGregg and a 1080p 42" Panasonic Viera on the shelf was $667. With 24 months free financing, it's $24 a month. More my style. I also saw the Sharp Aquos 42" for $1136, same deal at $48 a month. Still doable, but I fear that technology is "too new" to devote bucks to. Plus with the holidays coming, that could easily drop another $100-$150. I need to start a thread on that technology and see what people think.

Thanks for the find on Tri-State. That is even more reasonable and a 6 month warranty too. If anyone has experience with Tri-State, please feel free to chime in.

[Edit: FYI - Free shipping from Tri-State on orders over $100]

As always,



Q

[Wizard]

Re: Panasonic TH-42PX25 Digital HD Plasma dead

Good digging on diagnosis.

What is this DG module? I wanted to understand better because this does not make sense with the brightly colored strips across the panel.

Cheers, Wizard

[mockingbird]

Re: Panasonic TH-42PX25 Digital HD Plasma dead

Can I ask how you managed to remove the LC and replace it? I tried this one time and all I got was burnt finger tips and a sense of frustration.

[Quasar]

Re: Panasonic TH-42PX25 Digital HD Plasma dead

Wizard -

The service manual does not explain the boards, just names them. The description in the chart is "DIGITAL CORE, MICOM". Part number is TNPA3177AC. From the block diagram it is labeled "Micom, Digital Signal Processor".

It is interconnected via with:
H - REAR TERMINAL
DT - ATSC INTERFACE
DV - HDMI A/V INTERFACE
D - DIGITAL SIGNAL PROCESS (Pulling the connector from DG to this board produces a blank screen and the words "NO SIGNAL" in yellow on the screen.

Please also, your opinion on the set in this post:
https://www.badcaps.net/forum/showpo...8&postcount=11


-----------------------------------------
Mockingbird -

A bit of flux, a hot tinned iron, and a pair of tweezers. The chip actually stuck to the iron when it came loose.
I did the reverse when replacing it and used the flux to hold it steady. I used the tip of the tweezers to hold it to the board, tinned the iron and just touched each end.

Q

[Quasar]

Re: Panasonic TH-42PX25 Digital HD Plasma dead

Update:

Used a VCR video input and with the VCR just "on", the screen was a solid pink/magenta color like that in Post 21.

When playing the video, it appeared the same as when I was using the antenna/cable inputs with the horizontal bars/strips. Audio is fine and the bars change with the movie. OSD is still fine.

Since both of these boards interconnect directly to/with the DG board, I'm now more convinced that it's the culprit.

I'm trying to find a point where I could inject a video signal beyond that board to see if it changes or works.

I need the 42" screen to see the schematics in whole though... Just huge PDF's.

Q

[kevinm34232]

Re: Panasonic TH-42PX25 Digital HD Plasma dead

Had same problem, with same short on DG board, replaced board and all is good..

Update: TV picture went out after an hour, still powered on but no video and fans aren't going..

[fairwayrepair]

Re: Panasonic TH-42PX25 Digital HD Plasma dead 12 blinks

I got PANASONIC model TH42PX25 unit that was fixed analog video problem a few years ago, now it has 11 blinks of death, I found the inductor LC4330 shorted to the ground, it's located by the black connector DG23 on the DG board, I removed it and replaced with bypass wire, the set works fine now.