Philips 42PFL9803 - chassis Q529 - two blinks - shot FDS8884 FETs on main board - typical fault

The Philips 8000/9000 series from around 2010 are my favorites after the Panasonic NeoPlasmas. This one came in with the two blink code. The seller said it suddenly switched itself off and never came back alive.

Just look at this. Two fans and four decent speakers. Only one adhesive tape, the rest is done with clips. The power supply is built for eternity. Back in those days, TVs used to have a protective shield in front of the panel and the frame was rock solid. The golden age of LCD TVs.

Ok, service manual readily available at elektrotanya.com. The Philips manuals from those days are enormously detailed. They even explain the DC/DC regulator circuitry. Real engineering pride. They always give me good confidence to attempt any repair, even on board level. First thing to do with a dead Philips is to activate the SDM (service default mode). This is done by shorting the SDM point on the main board to ground:

The device will ignore a number of checks and keep running. Also, it will morse an extended error code via the stand-by LED. In my case it was 1 long - 8 short, which means code 18. Let's look it up:

Aha, so next task was to locate the DC supply circuitry on the main (SSB) board and measure. I found a broken fuse:

I measured the FETs right next to it and found 7U05 to be dead short. It was the 1.2V DC supply. All the FETs are FDS8884. Didn't have those in stock, but I had a number of FDS8880, which are from the same family, but can handle more current. After removing the FET I also did an A-B check on the two identical PWM chips on the underside and found nothing alarming. So the PWM chip could still be ok.

Now, for testing I connected a fuse holder with a 4A fuse and started the device. Klack klack - dead - blinking. The fuse blew again! Was I a little to hasty this time?

The FET was shorted again. Why? Because I was sloppy and did not properly check 7U06, which wasn't dead short but almost. This so-called 'lower FET' goes to ground and 7U05 goes to 12V plus. Therefore, this sucker killed my new FET by pulling it to ground.

Now this got me thinking again: if 7U05 goes short, which is connected to 12V and is feeding directly into the 1.2V line, 12 volts are hitting the processor! Even for a short period of time, this could be fatal for main processor's core. I also did some research on the net and that did not lift my spirits, either. In a number of forums I found a couple of similar cases with no good ending.

With mixed feelings, I replaced both FETs this time. I connected the board to my bench supply, limiting the current to 500mA. I first connected the 1.2V line directly and it only pulled much less than that. Chances were high that the processor was still good.

Then I connected the 12V feed. The DC/DC regulator came up ok and the board pulled a constant current around 550mA. Nice.

Back in the TV, I still kept the 12V feed connected to the bench supply. The TV wouldn't come up unless I raised the current limit to 1600mA.

But that did the trick. It was working again! I was lucky. No ICs fried. A cheap repair.

Hallo Frau Johansson!

This TV confirmed my opinion about the 8/9er series. Brilliant image! Totally even backlight, crisp colors, very high contrast. Like all LCD TVs I've seen, it does not match the natural colors of a Panasonic NeoPlasma. The viewing angle is a little critical, too. The colors quickly wash out viewed slightly from the top. Like many LED LCDs, it emphasizes reds a little. The software does offer a custom white balance, which does help somewhat.

The sound is powerful, homogeneous and spacey, thanks to four proper wide-band speakers.

Epilogue

I was lucky++. Later I found the following warning note in the manual:

And this:

These guys know their stuff!

I should have checked the FETs first. In my case, the fuse blew and they were inactive, anyway. But if they had produced over-voltage without blowing the fuse, I definitely would have fried the main processor. The main board is not available anywhere, not even in the most exotic countries.
Always fully read the fucking manuals!

As this TV had some mileage, I also had a look at the power supply's solder joints. None of them showed any signs of aging. As a precaution I re-soldered all FETs and diodes. All heavy and hot parts are mounted in rivets, the heat sinks are ridiculously over-sized. They get a little more than hand-warm at best.

A great machine. However, it seems to have trouble with the DC/DC stage sometimes and according to some voices on the net, it may fry its processor.

So what about the three blinks error code?

The same model was on eBay at the time, with a three blink error code. According to the manual, this means 12V supply failure. Your first instinct would focus on the power supply. But, from what I know now, I'd suspect an identical failure, albeit with no open fuse. The DC/DC stage might produce heavy over-voltage and there is nothing the protection circuitry can do about it except cutting the 12V supply. The warnings from the manual have to be taken very seriously. The question is: did the ICs survive the attack or not?

Samsung UE46D6200 - double image, ghost image - thin black horizontal line - panel defect

A friend sent me a picture of his Samsung and asked me if I could repair it. It suffered from double images in the upper half and a thin horizontal line on the lower third of the screen. He said that the line appeared first and the double images came later.

My first rule of TV repairs says: horizontal, irregular structures or single black lines are panel faults. They are caused by defects in the gate drivers, which are partially or fully shorted.

Knowing about the disastrous quality of the Samsung D series - I see a defect D with panel fault almost every week on eBay or eBay classifieds -  I had no doubt about it that this was yet another panel fault. I picked the TV up and took the opportunity for some investigation. Maybe it was a bonding problem and I could fix it with a hack.

The Samsung panel had no Y- (gate driver) boards and thus, no bonding on the left or right side to the panel. The only connection to the panel is made on the bottom of the screen, which drives both, the gate- and datalines.

The bonds and driver chips did not respond to any pressure or bending. They seemed ok. I also unplugged the two connectors to the TCON-board one after another to see if one side has the fault. Nope. The double image would not go away, regardless of what I did.

The problem with this type of panel are the gate drivers, which are inside the panel. On the glass, to be more specific. The semiconductors are sitting on the glass substrate. Absolutely no chance to repair.

So, this was a hopeless case. I removed all the boards, which had no fault, and dumped the rest. I also kept the nice thick plexiglass light guide sheet from the panel, this might come in handy some time.

My friend bought a nice Panasonic, which I recommended to him. I hope (and expect) that this one will last longer than the Samsung crap, which ran for ridiculous 3 1/2 years. Unless Panasonic bought panels from Samsung :-o

If you like to learn a lot about how LCD panels work, I recommend Ken Liew's ebook LCD/LED Screen Panel Repair Guide. It is a large, yet sometimes chaotic and hard to read - Asian English :-) - collection of tips and tricks on panel repair, written by an experienced practitioner. He spends some time explaining the cause of double images and suggests pretty wild hacks to revive the TVs, albeit with some loss in image quality.

The Asian repair guys generally tend to dig much more into the devices.

Toshiba 42SL738G - switches itself off - loose screws and potentially bad solder joints on power supply board

A friend got this TV from eBay classifieds. The seller said that after about 1h the TV would switch itself off.

A TV switching itself off when it is warm has either a problem with cold solder joints or some semiconductor is flawed. I didn't waste time waiting for that event and opened the set right away. First thing I noticed was the fragile plastic case. Not impressed.

Toshiba did not use any adhesive tapes here, applause for that! However, the power and logic board (the green in the center) were so ill-fitted to the chassis that they bent. Look at that:

Jesus, Toshiba! Seeing this directed my attention to the power board, which might have had a problem with cold solder joints. I did not see any obvious cracks on the joints of the FETs and diodes, nevertheless I re-soldered all of them, just to be safe.

None of the FETs and diodes had rivets in their solder joints. Boooh! This is very cheap and prone to fail eventually.

I also noticed that all screws besides the one of the backlight board were loose. This can cause problems when a ground screw is affected. It can even kill a TV (see Panasonic Plasma loose screws)

After tightening everything up, I let the TV run for half a day and a couple of evenings and it was flawless. At least electrically. The image suffered from the "dirty screen symptom". Look at the vertical, regular streaks:

They appear in regular distances, yet in alternating intensity. First I thought there was dirt in the panel, like it tends to accumulate in panels with CCT backlight, due to electrostatic charge and heat. However, in an edge-lit LCD TV there is neither of that. After some research I realized that this seems to be a well-known issue among all brands. The reason is the hunt for ever more contrast and dark blacks, which require aggressive filtering. If the filter foils in the panel do not perfectly align, those patterns appear.

This TV is a mixed bag. The image is quite ok, but suffers from the dirty screen symptom. The sound is very thin. The overall build quality is mediocre.

Considering the cheap price my friend got it for and the 0€ repair, this doesn't matter much.