Panasonic Viera TX-P42VT30E TNPA5330 blown
Hi all,
I apologize for the very long post, I don't know what came over me...
A few days ago my wonderful TV set ceased to work with a POP sound after 7 years of impeccable images. While working normally, the pop came and the TV shut down. After unplugging, resting a short while and re-plugging in, I only got a repetitive 7 red blinks of the power led, which I later discovered is called "Panasonic 7 blinks of death
.
As a guy concerned with quality over price I contacted the local Panasonic service center and described the problem. They offered me the P board at a price of about 200 euro as they said it is 100% defective and declined to quote anything else until the P board is replaced. They estimated the repair (off the record) to about 700-900 euro. When I asked them why the repair is close to the original TV price they said that they only replace the whole boards with Panasonic originals and they cost a lot.
Ok, given that you can find a decent new TV set with 900euros and I have some (limited) skills with the soldering iron and a digital multi-meter I decided to at least try to fix the TV. In case of failure or fire, I'll just head out to the store and buy a new one... but I love my Viera too much to just throw it away.
Looked up a service manual on the net and identified the 7 blinks code as SN-Board failure. Since I had no idea what a SN Board is, I started the search that lead me here, among other places. I read all about it and learned about the "screws that screwed up" my TV. (More info HERE)
So, I started by opening the back of the TV and cleaning the dust found inside. After a brief visual inspection, I found no culprit for the POP sound, so I started with the multi-meter.
The obvious (for me) point to start was the power source (P-Board). One blown fuse (4A) and two transistors shorted. So far, everything seemed to be coherent with other SN-Board failures found over the internet.
Next, I started to measure things on the SN Board (or YSUS board). After taking it out of the TV chassis I found the solder under the screws to be burnt exactly like others with the same problem showed it in pictures all over the net.
I did all the possible checks to ensure buffers are OK, no shorts found on the connectors, connectors with ground, no short on C842, etc.
Found 6 parts shorted (Q401, Q402, Q403, Q421, Q422 and Q423) and some SMD diodes near the buffers also shorted that I later learned they are supposed to show as shorted.
I ordered a repair kit with the risk of getting fake parts because my electronics skills are not that advanced to find in-production equivalents for the shorted and discontinued parts on my board.
The kit arrived and it was time for my temperature controlled soldering iron to go into action...
Since the 6 transistors are used in parallel (3 by 3), I re-checked every one of them after taking out from the board, just in case one of them survived.
No luck, 5 of them were still shorted and I found the POP source in Q423 that was physically cracked and showed an infinite resistance across all pins.
Since the recommendations were to also replace the driver circuitry IC502 and Q531 (and they were included in my kit), I found the courage to try and replace IC502 with my very unfit soldering iron and without a proper magnifying glass or light. I have no idea how to test the original IC502 so replacement was kinda mandatory. Q531 on the other hand seems to be in working order when measured on-board with the multi meter. Checked all the pins of the SMD IC502 and they show no shorts, all connections are according with the schematics (my eyes seem to be in decent shape, despite my not so young age ).
After replacing the above mentioned 6 transistors and one IC, I checked all of the gate resistors for the broken parts. They all show the correct value of 7.5 ohms. i also checked the resistors around the IC and found them all to be the correct value.
And now, finally, MY DILEMMA: No other parts show short or weird readings (except maybe Q661 which I will change today because it shows a strange leakage between the gate and collector). Should I replace all the other parts that came in the kit (19 total parts) or just the ones I was able to find broken?
Main cause for this dilemma is the amount of complaints about fake parts being included in these kits. My logic dictates me to try to keep as may original parts as possible, since those are certified. But how can I be sure I have tested them correctly and they are still working?
PS: Damn, I feel like I wrote a book here Sorry about that and thank you if you took the time to read until here
I apologize for the very long post, I don't know what came over me...
A few days ago my wonderful TV set ceased to work with a POP sound after 7 years of impeccable images. While working normally, the pop came and the TV shut down. After unplugging, resting a short while and re-plugging in, I only got a repetitive 7 red blinks of the power led, which I later discovered is called "Panasonic 7 blinks of death
.As a guy concerned with quality over price I contacted the local Panasonic service center and described the problem. They offered me the P board at a price of about 200 euro as they said it is 100% defective and declined to quote anything else until the P board is replaced. They estimated the repair (off the record) to about 700-900 euro. When I asked them why the repair is close to the original TV price they said that they only replace the whole boards with Panasonic originals and they cost a lot.
Ok, given that you can find a decent new TV set with 900euros and I have some (limited) skills with the soldering iron and a digital multi-meter I decided to at least try to fix the TV. In case of failure or fire, I'll just head out to the store and buy a new one... but I love my Viera too much to just throw it away.
Looked up a service manual on the net and identified the 7 blinks code as SN-Board failure. Since I had no idea what a SN Board is, I started the search that lead me here, among other places. I read all about it and learned about the "screws that screwed up" my TV. (More info HERE)
So, I started by opening the back of the TV and cleaning the dust found inside. After a brief visual inspection, I found no culprit for the POP sound, so I started with the multi-meter.
The obvious (for me) point to start was the power source (P-Board). One blown fuse (4A) and two transistors shorted. So far, everything seemed to be coherent with other SN-Board failures found over the internet.
Next, I started to measure things on the SN Board (or YSUS board). After taking it out of the TV chassis I found the solder under the screws to be burnt exactly like others with the same problem showed it in pictures all over the net.
I did all the possible checks to ensure buffers are OK, no shorts found on the connectors, connectors with ground, no short on C842, etc.
Found 6 parts shorted (Q401, Q402, Q403, Q421, Q422 and Q423) and some SMD diodes near the buffers also shorted that I later learned they are supposed to show as shorted.
I ordered a repair kit with the risk of getting fake parts because my electronics skills are not that advanced to find in-production equivalents for the shorted and discontinued parts on my board.
The kit arrived and it was time for my temperature controlled soldering iron to go into action...
Since the 6 transistors are used in parallel (3 by 3), I re-checked every one of them after taking out from the board, just in case one of them survived.
No luck, 5 of them were still shorted and I found the POP source in Q423 that was physically cracked and showed an infinite resistance across all pins.
Since the recommendations were to also replace the driver circuitry IC502 and Q531 (and they were included in my kit), I found the courage to try and replace IC502 with my very unfit soldering iron and without a proper magnifying glass or light. I have no idea how to test the original IC502 so replacement was kinda mandatory. Q531 on the other hand seems to be in working order when measured on-board with the multi meter. Checked all the pins of the SMD IC502 and they show no shorts, all connections are according with the schematics (my eyes seem to be in decent shape, despite my not so young age
).After replacing the above mentioned 6 transistors and one IC, I checked all of the gate resistors for the broken parts. They all show the correct value of 7.5 ohms. i also checked the resistors around the IC and found them all to be the correct value.
And now, finally, MY DILEMMA: No other parts show short or weird readings (except maybe Q661 which I will change today because it shows a strange leakage between the gate and collector). Should I replace all the other parts that came in the kit (19 total parts) or just the ones I was able to find broken?
Main cause for this dilemma is the amount of complaints about fake parts being included in these kits. My logic dictates me to try to keep as may original parts as possible, since those are certified. But how can I be sure I have tested them correctly and they are still working?
PS: Damn, I feel like I wrote a book here
Sorry about that and thank you if you took the time to read until here
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