Panasonic TH-42PA60A Self Test Failed

[mangozac]

Well my good old Panny plasma is playing up again. I should throw it out but I feel attached to it for a number of reasons, including the fact that is used to be my late beloved grandmothers and despite its age it still shows a really nice picture.

So it all started when about a week ago I began noticing red patterns appearing along certain contrast changes on the picture. This was regardless of input source. Check out the first picture for an example.



So I did some reading and found that apparently things like this can occur due to incorrect voltage adjustments. So I opened her up and checked the voltages. The Vsus and Ve voltages were a bit out so I adjusted them back into spec. While I was in there I decided to check all of the other voltages, including the 15V supplied to the SS/SC boards.

Since I live near the ocean corrosion is pretty significant and it's hard to get a good contact with the multimeter probes. I accidentally slipped and shorted out the 15V onto the base of a transistor on the SS board, completely frying it with a base to collector short. It turns out that this was one of the IGBT drive transistors and as such is a really high frequency part (5GHz). I was able to find a suitable replacement (BFQ149) which arrived today and I installed it tonight. To my elation the TV now works again, but I'm back to where I was before the self inflicted damage.

I did some more investigating and found an interesting result on the self-test. As shown in the second pic, the self test failed on the panel. Also note that none of the FPGA, EEPROM, MCU or PDROM versions are being reported.



I looked through the schematics and these all communicate with the main MICOM IC through a paid of I2C lines labelled "PANEL SCL 1" and "PANEL SDA 1" so I reckon it's safe to assume a connection issue. Especially since I have screwed around on that board in the past. I'll bring a scope home from work tomorrow night and do some probing.

The purpose of posting this here is to ask whether you guys reckon that the red patterns I'm experiencing would likely be related to the panel communication issue or something else? If something else do you have any suggestions?

Thanks for reading!

[tom66]

Re: Panasonic TH-42PA60A Self Test Failed

I would say it's more likely to be a loose connection between the A board and D board due to corrosion or being mis-seated. I'd recommend reseating all cables between the A and D board. It's possible the connector carries other lines, such as I2C, which are also going astray.

[mangozac]

Re: Panasonic TH-42PA60A Self Test Failed

Thanks Tom. I looked at the schematic some more and decided it should be an easy enough operation to just beep out the connections with the meter. Found that one of the 0 ohm jumper resistors had gone open circuit. I'm guessing I had physically damaged it during my last adventure inside the set and the recent cold weather had caused it to move just enough to go open circuit. So the self test now passes again, but unfortunately I've still got the red patterns.

Do you have any suggestions for them?

[tom66]

Re: Panasonic TH-42PA60A Self Test Failed

Try:

Hold VOL- or CH- on set, whichever your set has
Press "0" three times on remote
Release buttons and wait 10 seconds
Press red twice
Test pattern should appear does it look OK?
Press red each time to go through test patterns, do they look OK?
Unplug TV to leave service mode.

[mangozac]

Re: Panasonic TH-42PA60A Self Test Failed

Test patterns all look perfect.

[tom66]

Re: Panasonic TH-42PA60A Self Test Failed

In which case, the fault is either on the A board, the connection between the A and D board, or very rarely on the D board itself.

[mangozac]

Re: Panasonic TH-42PA60A Self Test Failed

This set has H and DG boards rather than an A board. Since the fault is occurring on all inputs - including HDMI - that would indicate an issue with the DG board, or more specifically between the output of the video processor on the DG board and the D board. I wonder if perhaps there is an issue with the LVDS connection?

I'll do some more digging and report back! As always the help is appreciated!

[mangozac]

Re: Panasonic TH-42PA60A Self Test Failed

Well it's a week on but unfortunately I've still not had any joy. I have found a couple of things though:

1. I've played around with all of the connections between the DG and D boards (including the LVSD pixel stream) and all seems perfect. The D board actually looks pristine and shows no signs of dust of corrosion.

The pixel data literally comes out of the main DG board processor, through some resistor networks, through the LVDS IC and out to the D board. The DG board is only a few months old and all of those parts seem fine.

I can't go just randomly replacing boards because they're simply not available. It seems that the Aussie model of this TV is very specific and I can't just grab boards from other countries' versions, because the processors will detect the mismatch and just not run at all.

2. In an attempt to try to further qualify the mode of the error I tried displaying the HDTV test pattern shown here. At first I received a vertical red line through just the yellow bar at around 170, but then it disappeared and began displaying on the red bar in about the same location. It's like the issue is caused by just a specific red value (since red values in the red and yellow bars are identical) but in that case you would expect it to be showing on both bars simultaneously.

3. The remote control has a freeze frame button on it. When pressed while playing a movie with the red pixels showing up (as shown in the first post), the red pixels remain on the screen and even sometimes move slightly. Would this frozen image function likely be performed on the DG (A) board or on the D board?

If the fault is being caused by the D board, is it possible that the test patterns generated by the D board don't show the fault because they just don't generate the kind of colour gradient that produces it?

4. There are two blown ceramic caps on the SS (sustain voltage) board: C6001 a 5.6nF 630v cap across the Collector-Emitter of IGBT Q6001. Here's that section of the schematic, parts of interest in the top right:



There are actually similar capacitors across Q6002 and Q6003 (the one across Q6002 doesn't look too healthy either), not shown on the schematic. Ultimately they're all in parallel anyway. I assume these are just for EMI suppression rather than any function of the panel's operation? I could source replacements, but 630V ceramic caps aren't exactly a common item so I'd rather wait until I know I can sort the main issue first (unless of course it's possible that this is causing the issue).

Any suggestions on how I can further try to diagnose this down to a component level or is it time to give up?

Zac

[tom66]

Re: Panasonic TH-42PA60A Self Test Failed

3. The remote control has a freeze frame button on it. When pressed while playing a movie with the red pixels showing up (as shown in the first post), the red pixels remain on the screen and even sometimes move slightly. Would this frozen image function likely be performed on the DG (A) board or on the D board?

Does this happen on analog sources, HDMI sources or both? It sounds like dithering, which is performed by the D board, and something with the dithering is going wrong.

[mangozac]

Re: Panasonic TH-42PA60A Self Test Failed

All sources. A problem with the D board would be a pain...

[mangozac]

Re: Panasonic TH-42PA60A Self Test Failed

Right after considering the issue I think that there is enough reason to try replacing the D board. At first I was concerned because the repair manual lists the D board part number as TZTNP01BMTB, which when Googled is nonexistant. But that's not the part number on the board! The actual PCB number is TNPA3932.

So TNPA3932 boards are fairly readily available. I assume that the TZTNP01BMTB refers to the TNPA3932 that has been programmed specifically for this 42" panel, which can be problematic if I just grab any TNPA3932 board available. Theoretically there's nothing market specific about the TNPA3932 and the schematics specify the same board is used in both 42" and 37" models. So it would be worth trying a direct swap, however I reckon it's very possible that the DG board will detect an incorrect ROM version and give a single blink code.

As best I can tell there are 3 ROM chips on the board:
IC9007 PROM(FPGA) with firmware TVRN941
IC9001 EEPROM for the MICOM processor with firmware TVRN806
IC9303 16M Flash memory IC to FPGA with firmware TVRN815

So assuming there is no circuitry differences (like the various suffix DG boards) theoretically it would just be a matter of swapping over these 3 ICs (or at least those with different firmware stickers on them) to have the new board function the same as the old one.

Can you spot any flaws in my logic? Is it worth the $100 to get a replacement D board or is it time to put this 7 year old SD TV to the grave? It sucks that that's only about a 10th of what a similar sized replacement TV would cost! But at this stage I just want to get it going "because I can"

[tom66]

Re: Panasonic TH-42PA60A Self Test Failed

I don't know about Aus prices but a 42" 1080p plasma here is only around $500 to $600 US equivalent, and I can buy a 42" standard definition plasma like this for around $50 used.

[mangozac]

Re: Panasonic TH-42PA60A Self Test Failed

TVs are a little more expensive here, but a similar sized Panasonic is around the $1k mark.

I just had another look at the image and the red pixels seem to be getting worse. They show up on any transition from a lighter pixel containing red to a darker pixel in the scan direction (left to right). Even the OSD menus, etc. have it. But the internal test patterns are fine.

The fault is somewhere between the DG and D boards and without the ability to swap out test boards all I'm going to be doing is throwing money down the drain. I'll keep an eye on the classifieds for when a local broken one gets listed (they are a pretty common TV here and I just contacted one local ad for one but they had already binned it) that I can do some part swapping with. At least I know all of the important bits like high voltage and power supplies work.

In the meantime I've got an LG LCD of my parents' with a dead power supply that I'll fix. I've tracked down the fault as a dead STBY5V supply switching controller and have got a new one on the way from China.

It's a good thing I'm not a big TV watcher - I mainly use it for movies...

[tw2005]

Re: Panasonic TH-42PA60A Self Test Failed

Anywhere near Brisbane?

http://www.ebay.com.au/itm/PANASONIC...item33844fec04

could aslo have a bad DG board, does not turn on.

[mangozac]

Re: Panasonic TH-42PA60A Self Test Failed

Brisbane is an hour away but the hassle is that I can't fit big TVs in my car! I'll find out what suburb it's in and give it some thought - certainly if I can pick it up for a dollar it might be worth picking up...

[tw2005]

Re: Panasonic TH-42PA60A Self Test Failed

It's a relist, so good chance you'll get it cheap being fairly old now and analogue I don't think there'll be too much interest. Should fit in the back seat of most vehicles unless you have a ute?

[mangozac]

Re: Panasonic TH-42PA60A Self Test Failed

No, it would fit into the tray of a ute at least - I drive a 2-seat sports car. I measured and the 42" display won't fit into the boot and definitely not the passenger seat. There's no space behind the seats either.

Might have to talk the girlfriend into a day down to Brisbane and put it on the back seat of her Focus

[mangozac]

Re: Panasonic TH-42PA60A Self Test Failed

What the hell that ebay auction is suddenly rocketing up in price! It's at $20 already! Might have to move on from that one!

[tw2005]

Re: Panasonic TH-42PA60A Self Test Failed

What the hell that ebay auction is suddenly rocketing up in price! It's at $20 already! Might have to move on from that one!

Yeah, no bids one week and plenty the next. Could be some funny business, bidding up their own item?

there's another on the Gold Coast but really a TV at this age and analogue. How far do you go?

I've got a 2005 PA50 which i don't ever expect to find a DG board for, only hanging on in hope for a mate who's it was and is broke.

If you're into this thing look for something fresher but I appreciate there's possibly some sentimental value in this one for you.

[mangozac]

Re: Panasonic TH-42PA60A Self Test Failed

I thought maybe some funny business too, but the bid history shows 3 bidders so I would think it maybe less likely.

There's one on Gumtree on the South side of Brisbane (the guy wants 60 bucks), but like you say, where do you draw the line. It's an old, analogue, standard def TV and while it does have some sentimental value, I'm not one to waste money due to sentimentality (not to brag, but I have no cash issues preventing me from buying a new TV). Once the replacement part of the other LG LCD I'm fixing comes in and I see if I get that working I'll be in a better position to assess what I want to do with the Panasonic.

Here's a laugh: this guy wants $650 for the 42PA60A without a remote! http://www.ebay.com.au/itm/Panasonic...item4609e48e2d