Panasonic TX-P42ST30E - TNPA5330 board defect - seven blinks and six blinks of death

The Panasonic Plasma 30 series (ST30, GT30, VT30) all suffer from a very silly bug: the ground screws of the SN (scan + buffer board) go loose and eventually produce sparks, which will kill a whole bunch of semi-conductors on the SN board and probably on the power supply board, too.

(In the meantime, I have analyzed this defect in more detail HERE)

The symptoms are 7 or 6 blinks of the standby LED. The service manual says:

A new SN board is prohibitively expensive. I did not find any under 230€ on eBay. In other models, Panasonic used to split the buffer board from the scan board. Here though, it is all in one and the buffers make it so expensive.

Luckily, there are repair kits on eBay tailored for this problem. I got one from GTV Watford in Great Britain. Including shipping it cost me 83€. The TV itself  was only 45€.

The following image shows the shot parts on the TNPA5330 SN board. The red marks are the parts covered by the repair kit, the yellow mark is a transistor, which is not included in the repair kit.

That's not all. Due to the diodes and transistors going short on the SN board, the power supply board blew a fuse and two FETs also died. See next image. For this, GTV offers another repair kit.

My brand new pre-heating plate and hot air gun finally got something to work on:

I covered the capacitors with capton tape and heated the board up to around 140°C. With the hot air gun set to 420°C the SMD-mounted large semi-conductors came off quickly and without a problem. For soldering, I used solder paste and the same temperature settings. It is fun to see the big thingies snap into place once the paste has reached its melting point.

Replacing the fuse and the FETs on the power supply:

After replacing the large diodes and transistors, I ran a test and still got 7 blinks. So I fitted the remaining two parts from the kit also. They are a switcher IC and a double transistor. This pair occurs in all four energy recovery or sustain circuits, respectively.

After I had used all the parts from the repair kit, the TV ran fine for a couple of minutes and then suddenly switched off again, this time with 6 blinks instead of 7 blinks! What was going on?

I checked all the scan and energy recovery circuits again and lo and behold, I found Q451 with a short between Gate and Collector. It is part of the RECOVERY-L section. Apparently, it had been already pre-damaged and finally broke during my first test run.

This particular transistor was not supplied by the repair kit. In foresight, I had ordered a working SS-Board on eBay, which is the little sister of the SN board and contains most of the same semi-conductors except for the expensive buffer chips. The SS boards are cheap. Mine was 30€. The SS board had two DG302 transistors on it and so I picked one from there.

In hindsight, it would have been cheaper to order two SS boards, which I think would cover even more than the necessary parts, instead of the repair kit.

This is what it looks like when one of the panel connectors is not seated properly. Thin horizontal lines all over the screen (the boxes are from the screen menu).

Those connectors are not so easy to seat. It takes some practice and I recommend using a magnifier glass to check that the little notches on the connectors are actually all the way in.

And now the Plasma does what it can do best: producing rich and beautiful colors:

It was quite some work this time:

To help with cooling, I glued small heatsinks on the large semiconductors and buffer chips. The heatsinks are not very powerful, but better than nothing at all. There is no space for large heatsinks, anyway.

A few words about the Panasonic service manual. The images for the boards and circuits are too small and not zoomable vector graphics and you can't see any of the small labels properly. Repairing a mainboard with this material is practically hopeless. The SN board is relatively simple and it did not matter. A mainboard is much more complex and you need all the fine details. Maybe there are copies around with better quality. I for sure did not find any.

The manuals from Sony and Philips which I have are much better. Personally, I would refrain from buying a defect Panasonic with a potential mainboard or logic board problem.

This TV is a keeper. It is missing DNLA features, but I will rather buy one of those Android quad-core devices with WiFi and HDMI, which have better performance and software on board than any of the Smart TVs out there.

Don't forget to improve the screws, folks! Replace the originals with new, longer screws with spring washers. Otherwise the same disaster might happen again.