Samsung 42" Plasma ps42c450b1wxxu very weak picture

[tom66]

Okay, so I got this Samsung Plasma TV model ps42c450b1wxxu off someone hoping to repair it and maybe resell it. It's about 6-12 months old - Samsung still sell this same TV! Anyway, when powered on you can hear the Samsung chime (or melody, whatever it is) but the picture is completely dark.

That is, until you turn the lights out. Then you can see a faint glow in certain areas, and various red/green pixels flickering. There is no buzzing, apart from the faint SMPS buzz. After a few minutes, sometimes half a "no signal" display flickers on the screen, but that too is very dim (just about visible with the lights on.) The TV is fully responsive during this e.g. you can navigate menus (and the faint display will flicker slightly) and you can turn it off.

I've heard of this problem before, so I suspect the Z-sustain (I think Samsung call it the XM board, but I'm not sure.) Am I right in suspecting this? Are these boards repairable, or are they just "black boxes" to replace?

I found this replacement board: http://www.ebay.co.uk/itm/5288-SAMSU...item4cf84e7654

That will cost around £40, which is pretty reasonable for this TV (retail £360), but I want to be certain it is the board that is faulty.

[PlainBill]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

Okay, so I got this Samsung Plasma TV model ps42c450b1wxxu off someone hoping to repair it and maybe resell it. It's about 6-12 months old - Samsung still sell this same TV! Anyway, when powered on you can hear the Samsung chime (or melody, whatever it is) but the picture is completely dark.

That is, until you turn the lights out. Then you can see a faint glow in certain areas, and various red/green pixels flickering. There is no buzzing, apart from the faint SMPS buzz. After a few minutes, sometimes half a "no signal" display flickers on the screen, but that too is very dim (just about visible with the lights on.) The TV is fully responsive during this e.g. you can navigate menus (and the faint display will flicker slightly) and you can turn it off.

I've heard of this problem before, so I suspect the Z-sustain (I think Samsung call it the XM board, but I'm not sure.) Am I right in suspecting this? Are these boards repairable, or are they just "black boxes" to replace?

I found this replacement board: http://www.ebay.co.uk/itm/5288-SAMSU...item4cf84e7654

That will cost around £40, which is pretty reasonable for this TV (retail £360), but I want to be certain it is the board that is faulty.

The symptoms match those of a bad Z-Sustain - the board on the right side as you stand behind the TV. The board looks like it would be repairable, the problem is determining which component is bad.

PlainBill

[tom66]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

The symptoms match those of a bad Z-Sustain - the board on the right side as you stand behind the TV. The board looks like it would be repairable, the problem is determining which component is bad.

PlainBill

Are there a set of tests I can do on the Zsus to determine if it is faulty?

This was the right hand side board and it is smaller than what I think is the Ysus. I'll get an overall layout picture later.

[tom66]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

Since the TV is less than 12 months old, it must be covered by warranty. I have no idea whether they did claim on it or not. I saw they had a new TV (an LG) so I'm really not sure if they got it replaced and were allowed to keep the old one, or if they bought a new one. But surely there's the minimum 1 year warranty in EU?

Is it possible to order the Zsus part direct from Samsung, perhaps for free under the warranty?

What do these boards, such as Ysus and Zsus, actually do? From what I have read, the Ysus drives the rows through the buffers. I'm not sure how the X buffer comes into it, perhaps it selects the columns. And I think the Zsus is involved in the discharging of the pixels? Or am I completely off the mark here?

[PlainBill]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

Since the TV is less than 12 months old, it must be covered by warranty. I have no idea whether they did claim on it or not. I saw they had a new TV (an LG) so I'm really not sure if they got it replaced and were allowed to keep the old one, or if they bought a new one. But surely there's the minimum 1 year warranty in EU?

Is it possible to order the Zsus part direct from Samsung, perhaps for free under the warranty?

What do these boards, such as Ysus and Zsus, actually do? From what I have read, the Ysus drives the rows through the buffers. I'm not sure how the X buffer comes into it, perhaps it selects the columns. And I think the Zsus is involved in the discharging of the pixels? Or am I completely off the mark here?

You have neatly encapsulated my understanding of the function of the support boards of a plasma panel into one paragraph. I think it might be more accurate to say the Z-sustain precharges the cells (pixels). If you Google 'Plasma Training Manual' you should be able to find excellent manuals that discuss this in detail.

PlainBill

[tom66]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

You have neatly encapsulated my understanding of the function of the support boards of a plasma panel into one paragraph. I think it might be more accurate to say the Z-sustain precharges the cells (pixels). If you Google 'Plasma Training Manual' you should be able to find excellent manuals that discuss this in detail.

PlainBill

That makes a lot more sense. So Zsus is involved in the precharge, and discharge of the pixels. With a bad Zsus, the picture would be very dim, as it is.

Luckily there are no IPMs in this TV. It's all discrete MOSFETs and diodes. So not too difficult to replace those.

I'm having a little trouble, though. I reinstalled the Zsus, but now when I power the TV on it's completely black - nothing when the lights are out either. It's still making the melody and will turn on and off. I'm guessing I've disconnected something somewhere that I shouldn't have, or maybe completely killed the Zsus from ESD or something similar .

I have an oscilloscope so I can check drive waveforms but my scope is rated 250V max, I don't want to blow it up. I will need to use a x10 probe, right?

I'll look at contacting Samsung about this...

[Toasty]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

Could this be a bad panel? Lost its gas?

[rayrod81]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

I have seen a couple of plasma TVs with these symptoms that had a bad panel. One was a Panasonic and one was a Samsung. I am guessing the newer, thinner panels are more susceptible to cracking around the edges and slowly leaking gas causing the exact symptoms you describe.

It could still be the Z-sustain but I am slightly skeptical because the new Samsungs I have seen and worked on will shutdown and go into protect if either the Y-sus, buffers, or Z-sustain is bad. The best way to check the Z-sustain is to test the mosfets and rectifiers for shorts. If you do find a shorted component then the hardest part may be finding one for purchase as I have found it is hit and miss. Then again these boards are actually relatively cheap to purchase and replace.

As for being able to get a board from Samsung through a warranty repair, they won't send you one unless you are a Samsung Repair Center. You may be able to get it repaired under warranty through a service center but it is highly unlikely without a receipt.

[tom66]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

Could this be a bad panel? Lost its gas?

I have seen a couple of plasma TVs with these symptoms that had a bad panel. One was a Panasonic and one was a Samsung. I am guessing the newer, thinner panels are more susceptible to cracking around the edges and slowly leaking gas causing the exact symptoms you describe.

It could still be the Z-sustain but I am slightly skeptical because the new Samsungs I have seen and worked on will shutdown and go into protect if either the Y-sus, buffers, or Z-sustain is bad. The best way to check the Z-sustain is to test the mosfets and rectifiers for shorts. If you do find a shorted component then the hardest part may be finding one for purchase as I have found it is hit and miss. Then again these boards are actually relatively cheap to purchase and replace.

As for being able to get a board from Samsung through a warranty repair, they won't send you one unless you are a Samsung Repair Center. You may be able to get it repaired under warranty through a service center but it is highly unlikely without a receipt.

I hope not. I don't think it is, because when it does display the no signal picture it is all distorted and half of it is missing, it also flickers occasionally.

I thought most plasmas with bad panels don't give a picture at all? This one does give a faint image (well, not a picture as such, but there's something there.)

Anyway, I just noticed a silly mistake of mine. I forgot to connect the ribbon from the PDP controller board to the Zsus. If you look at the overall pic you will see my mistake (I was tired last night !) Now when I plug that back in, I get the original symptoms: faint glow, random firing of red and green pixels (and sometimes white - all three subpixels at once), varying dark and light patches across the whole display and after a few minutes a faint no signal display appears. It's best viewed in the dark, although the sun hasn't set yet so I can't show that on a picture.

I tested the panel voltages. Vs=209.5V (rating: 207V), Vsc=-198.6V (rating -197V), Va=52.4V (rating: 54V). So those seem good.

Faint buzzing sound from the sole yellow transformer on the Ysus, generates the Vscon voltage.

I thought Samsung would have learnt their lesson with the bad caps problem but no, this set is full of Samwha, Samyoung, HEC and the occasional CapXon.

I'll upload a video later showing the exact problem with the TV.

[tom66]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

Video: http://www.youtube.com/watch?v=Bmu12mCOKcU

I was fiddling around with it, but now it won't turn on at all, until I unplug the Zsus. It makes a continuous ticking sound. I think the Zsus has given up entirely, becoming shorted.

Anyway, before this happened, I plugged it into a PS2 for a video source, and the picture works - but it's extremely blocky. Hard to describe, but large areas of the picture freeze, and flickering lines run across the display. It's almost like a bad main board or PDP controller...

Can a Zsus partially fail and then give up entirely, becoming shorted?

When plugged in without the Zsus the panel briefly flashes but then doesn't do anything although the TV does respond to commands and it makes the chime.

[tom66]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

Okay so I removed the failed Zsus and find Q4007 is shorted, all pins have continuity to each other. It's a RJH30E2.

I can't find much info on this MOSFET; any ideas on an equivalent part?

A simple fix would be a new Zsus. I'll order that if I have no luck sourcing the right FET.

[Toasty]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

Get the service manual and try the search on the Samsung part number.

http://elektrotanya.com/?q=showresul...oria=&kat2=all

Utsource shows it as a RFQ item:
http://www.utsource.net/ic-datasheet...2-1867924.html

Toast

[tom66]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

Get the service manual and try the search on the Samsung part number.

http://elektrotanya.com/?q=showresul...oria=&kat2=all

Utsource shows it as a RFQ item:
http://www.utsource.net/ic-datasheet...2-1867924.html

Toast

Have that manual. But it's a powerpoint presentation with troubleshooting and flowcharts. No schematics. Also no info on what happens when the picture goes funky like in the video.

[rayrod81]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

That seems to be a common failure point on these boards. The only place I have found that MOSFET is Electronica. The web address is www.electronica-usa.com. I purchased a few a couple days ago and they were $6.95 each. Not sure if shipping will be prohibitive or not but its worth a try.

[tom66]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

That seems to be a common failure point on these boards. The only place I have found that MOSFET is Electronica. The web address is www.electronica-usa.com. I purchased a few a couple days ago and they were $6.95 each. Not sure if shipping will be prohibitive or not but its worth a try.

I've gone ahead and ordered a new Zsus because I found a low price for one. So I will see if that fixes the problem.

Seems strange it would give partial problems - then die completely.

[tom66]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

Great!

A "new" Z-sustain fixed the problem

TV now powers up and gives a good picture. Z-sustain only cost £14.80 (must be a used one at that price), and the TV was £50 so I'm quite pleased, a <12 month old 42" plasma TV for ~£65.

However, when powered on cold, the display has quite a few sparklies (red and green pixels, randomly firing.) Also, some of the pixels are "stuck", for about 10 seconds. When it was faulty, it had the sparklies too, so I'm wondering if it's a sign that something needs to be adjusted? Maybe the Z-sustain needs some settings adjusted to work with a different panel? Do I need to adjust Vs, Va, -Vsc etc., or can the required adjustments be made from the service menu?

After warming up for a few minutes the problem is almost completely gone, picture perfect.

Very interesting these new TVs come with a USB port. I tried it out and it works fairly well. But it's still not going to obsolete my HTPC.

[RJARRRPCGP]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

the picture works - but it's extremely blocky. Hard to describe, but large areas of the picture freeze, and flickering lines run across the display.

Sounds like when you watch DirecTV during a T-storm. lol.

[tom66]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

Here's a picture of the stuck pixels.

Odd thing: These stuck pixels appear when the picture is dim. But once it becomes brighter, the stuck pixels are erased, and they do not return until the TV is switched off for about 10-20 minutes.

I'm thinking something to do with the erase control? I know the Z-sustain is involved in the erasing of the pixels, so... Is it a problem with the Z-sustain?

Also, this TV runs Linux???

That's just... overkill. I use Linux (Ubuntu) on my laptop, but I wouldn't have thought it would suit a TV much.

That's interesting because a Smart TV sells for quite a bit extra. I'm wondering what the difference is between them, given this one seems to have a quite powerful processor. Although the #1 complaint I hear about smart TVs is they are sloooow...

Uses a lot of open source libraries, too.

[tom66]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

Well, I see two controls, Yfr and Yrr, on the Y-sustain.

I adjusted Yfr one way and the picture persistence got worse; I turned it the other way and it improved slightly. Could this be my issue? Bad timings?

I could check the timings with my scope, just got to figure out the high voltage stuff. Don't want to blow it up.

[tom66]

Re: Samsung 42" Plasma ps42c450b1wxxu very weak picture

Left the set off all night, then turned it on this morning: No problems with persistence any more! So adjusting Yfr fixed the problem after the Zsus was replaced.