Samsung PS43D450 / 642AX-YB11 Dead

[sean0118]

Hi everyone,

Fixing this Samsung PS43D450 for a friend, died with a loud bang while he was watching it.

All the boards seem okay, except for the Y-SUS (model: 42DH YM). Top layer has a shorted through hole RJP63K2 and snubber capacitor (hole blown in side). Bottom layer has some shorted surface mount SF5A400HD and IRG7R313U.

Is this a known issue with this model? The circuit is quite confusing, the ERC (energy recovery circuit) makes it complicated. Anyone have a schematic? Any tips?

[dick_barton]

Re: Samsung PS43D450 / 642AX-YB11 Dead

Do you have a cracked solder joint or is it just the lighting?

[dick_barton]

Re: Samsung PS43D450 / 642AX-YB11 Dead

double posted

[sean0118]

Re: Samsung PS43D450 / 642AX-YB11 Dead

Do you have a cracked solder joint or is it just the lighting?

It looks suspect, but I don't think it's actually cracked, just doesn't have enough solder. Hard to tell from the photo but it's one of the legs from the heatsink.

Some of the shorted SMD transistors on the bottom side also looked suspect, looked like there were hairline fractures on some of the tabs, but would need microscope to confirm.

Replace all the screws on the Xsus & Ysus before running up the set.

Yep will do.

[sean0118]

Re: Samsung PS43D450 / 642AX-YB11 Dead

Hi all, I've just replaced all the components mentioned in my previous post.

Now it turns on, but there is yellow dots all over the bottom left of the screen, green dots along the top and has some random noise all over the picture. It seems to get worse the longer the TV is on.

I've checked Va (+58V), Vsc (-185V) and Vs (+207V) which all match the sticker on the panel.


Any ideas?

(Please note the purple bar across the screen in one of the pics is just from the camera)

[sean0118]

Re: Samsung PS43D450 / 642AX-YB11 Dead

Another update, I discovered the test picture option in the menu, it ldoesn't looks so good! It seems to have made the image even worse, as it now has red, green and yellow dots since I viewed the test picture! lol

The second pic is of the scrolling bar (designed to fix burn in) but this didn't seem to help...

[tvtimmy]

Re: Samsung PS43D450 / 642AX-YB11 Dead

On that model, a bad ymain can take out the xmain too. I would check everything on the xmain.

[sean0118]

Re: Samsung PS43D450 / 642AX-YB11 Dead

On that model, a bad ymain can take out the xmain too. I would check everything on the xmain.

Thanks, I had another look but still couldn't find any issues on xmain, I resoldered the main power inductors pins to be safe but didn't change the picture quality.

After reading this thread I change Vs to 215V and Vsc to -200V. That has helped a lot! The test image only has a very small amount of pixelation now.

The next problem is the USB port is damaged so I can't update the firmware...

[sean0118]

Re: Samsung PS43D450 / 642AX-YB11 Dead

Good news! I managed to replace the USB port and upgrade the firmware from 1006 to 1029 and it's helped a lot! Only some strange pixels at the very top left of the test image now. I'm going to leave it on for a few hours to see how it goes...


Should I try to turn Vs and Vsc back down? Which one is more important to be lower?

[sean0118]

Re: Samsung PS43D450 / 642AX-YB11 Dead

It works pretty well now, I left Vs = 215V and Vsc = -200V and I changed the 'Picture Mode' to 'Entertain' which bumps up the contrast and cell light, this helped a bit too.

But it's still not 100%, the image is still noisy and has some weird pixels, mostly when there is a border of a light and dark area... it causes some faint lines of strange coloured pixels.

Any ideas? Is it safe to turn Vs and Vsc up higher?


edit: Managed to get a pic, turns out that the problem is particularly noticeable with the colour scheme of this forum.

[Andrew F. Ali]

Re: Samsung PS43D450 / 642AX-YB11 Dead

I would try returning the Vs and Vsc and any other voltages tampered with to the original settings or to that on the panel sticker

[sean0118]

Re: Samsung PS43D450 / 642AX-YB11 Dead

It was worth a try, but turning the voltages back to the default resulted in a really bad image again. I guess the firmware update by itself was not enough to fix it.

edit: I forgot to mention, I do have an oscilloscope, so if there's something I can scope out to debug let me know!

[sean0118]

Re: Samsung PS43D450 / 642AX-YB11 Dead

I scoped out the supply rails, both Vsc and Ve had soome very high frequency noise on them, too high for my 75Mhz scope to get a clear image of. I guess it might be normal, I tried changing some capacitors, but that didn't improve the picture at all. I would investigate it further, but I want to give the TV back.


I've bumped Vsc up to -201V (from -185V) while leaving everything else as default (Vs = +207V, Va = +58V, Ve = +103V). This gives a decent image (but still soem maldischarge) is it safe to leave it running these voltages?