Sunday, February 13, 2011

HP PL4260N suddenly lost picture - how to identify failed sustain boards

Synopsis: this article discusses the most popular failure in HP PL4260N (and the bunch of other TVs based on the same plasma display set by LG), the means to diagnose which board has failed and provides links for repairs / replacements for the failed boards.

Question:  I have an HP PL4260N plasma TV  (purchased 2006)  that has suddenly lost picture.  I don't know whether sound is still there since it is run through a home theater receiver.   I have taken the back off and none of the fuses are blown and there is no obvious bulging of any capacitors ( with one possible exception of a large 450v, 330 mf capacitor... it is so very slight that it may not be a bulge at all).  All fuses (there are 5) show continuity.  When the on switch is pressed it turns blue and then back to red.  No picture at all.
I have read your very interesting blogs but have found nothing specific to my Hp model... some say is was actually manufactured by either Samsung or LG.  I realize the information I'm giving you is sparse but from what I've read, I assume the failure of the Y an X boards as well as the power supply involves the failure of their fuses.... as mentioned, no failure noted.  Should I go ahead and replace the suspicious capacitor as the first step?  What can I do to determine the faulty board or combination of boards and what would each cost to repair.  Also, if a board tests OK by you, what would the charge be for the testing?

Answer.  Yes, this is likely a YSUS or a ZSUS board on your PL4260N.

(for those who do not know what YSUS and ZSUS are, here's a quick pictorial guide:)

A blown fuse is the most common and apparent indicator of a failed board, however sometimes a board can fail without blowing a fuse.

So while a blown fuse is a guarantee of a failure, the lack of a blown fuse is still not guarantee of anything.

Since your TV refuses to power on (going blue and then back to red) that would suggest the faulty board is shorted. When the power component on it has failed, a power semiconductor element there (one or more) have melted and has created a permanent (short) connection between power input and ground.
This is one of the possible outcomes of a power component failure and should not be taken for granted in all cases of a failure, but is still a very common one.

The same shortage is the reason why fuses blow in the first place. In your case, as we said, the power supply board has responded faster than the fuse and shut itself off.

Now when powering on it again detects the short before releasing full power voltage in that circuit and shuts off, which is why you see the TV going from blue back to red in a very short time.

When there is no burned fuse on either sustain board there are two major possibilities for a failure:

1) When the TV would not come on at all
That would indicate that a board has failed and shorted a major power line, but did not blow a fuse and as a result when TV is turned on, the shortage is detected by the power board and it automatically shuts itself down.

It is very easy to figure out the failed board since it prevents the TV from coming up: all you have to do is disconnect first one of the boards from power, say the YSUS board, and attempt to turn on the TV.
If the TV comes on and stays on (of course without anything on the screen) then the disconnected board was the one that was stopping it.

If the TV keeps on doing the same then connect the board back to power and disconnect the other one, then try to power on again.

If TV comes on this time then you've found your faulty board and if it still doesn't then the problem is most likely in neither of the sustain boards (although it is theoretically possible that both of them are bad).

Another simple way to find the failed board is to use DMM to measure resistance between Vs and GND pins on the power connector of the board. Zero or low (ohms) resistance in both directions indicate a failed board.
Please note that this is not the only possible short a board may develop, only the most common one.

2) When TV would come on with black screen or , sometimes, very dim, washed out screen
This is actually the more common failure than the above.
Dim and washed out image is most commonly caused by a failed ZSUS board.
If there is nothing on the screen, however, it could be either the YSUS or the ZSUS board that is bad (and very rarely both of them).

The easiest way to test which of the two may be bad is to let the TV run for 5-10 minutes (with dark screen) and then feel the heat sinks on both boards with your hand.

The one that is not hot is probably the faulty one.

If both are hot then the best thing to do is to send both of them for complete test in an actual working unit.
It is worth noting that a good number of times when the board fails it does not end up being short. It is still malfunctioning, but not necessarily short. Even more, sometimes it may have blown the fuse and still NOT be short. So if you replace the fuse you'd be able to power on all right, but still without an image or - sometimes - with a flashing light on the screen or other defects.

Once you figure our which board is bad - or if you can't figure it and need to check both - feel free to send them over to Coppell TV Repair (see section below) or, of course, any other vendor of your choice.

It is also worth noting that the same thing is going to happen on your other sustain board, so you may consider doing a service on both - one because you must and the other one in advance.

Here's a link to another article discussing the pros and cons of servicing one versus both sustain boards:

UPDATE: here are a few tips on disconnecting the Y-sustain board hopefully without damages:


We have separate offers for repair of the YSUS and ZSUS boards, however should you decide to do both of them simply send both together, that's all.

YSUS repair:

YSUS exchange:

ZSUS repair:

Hope that was helpful!

See you soon!


Anonymous said...

Hi Folks, how can i post to you a repair Question on a model you blogged on previously. I have an Hp pl4260n plasma which powers on , no pic, and for sound not sure, i plugged headphones into the reciever sound output rca's and the speaker outputs and hear donly popping when powering on and off, i cannot change a channel or a volume i really dont hear anything while its on , just pops when going on and off. Also the ysus has 2 steel blanks where the fuese go, the zsus has originals that seem to be good.I still feel like I should buy 2 of the replcement hybrids and a pak of fuses, whats your opionion? Does the no sound make you think differently or am i on track?

i have done about 4 lcd monitors as cap jobs no problem, and 2 small tv's with fuses and cap issues. Not much Electronic training otherwise, Im disabled and dont wanna make a lousey choice trying to choose which way to go with this.

please advise as I know you folks have alreadt blogged on this model and its lousey boards.

Steve B. or gmail

Unknown said...

This thread was extremely helpful Thanks! My PL4260N had the same swollen capacitor and a blown fuse on the ZSUS board. I was going to replace the capacitor before I read this thread then I went straight for the new ZSUS board and the unit fired right up when that new board went in.

The set is working but now has what looks like sparkling red digital snow in the picture. I have seen references to checking the Va and Vs voltages and setting them a volt or two below spec to address this but I have also seen references to replacing the YSUS board. What are your thoughts and what is the correct way to test the Va and Vs voltages?

Mike said...

Wonderful! Thanks for the detailed troubleshooting points. This is by far the simplest and easiest tutorial I've found for diagnosing a television. cable assemblies UK

Wendelb said...

Just wanted to say how grateful I was to find this service. I was able to avoid purchasing a new tv which was greatly appreciated. I would occur with the advice to send in both boards at the same time. I didn't and I only delayed my repair because I had to send in the other board anyway. Great service at a fair price.

Anonymous said...

Is there a trick to disconnecting the Z-sus board from the HP PL4260N? I can get the Y sus board out easy. But, there are these thin, copper sheet-like cables connected to the Z sus board. I don't want to break anything disconnecting the board, but I also want to get it repaired. Could use a tip here!

dcapper said...

I had the common no video but sound problem on my Akai PDP42z5ta. I replaced the fuse and STK chip on the YSUS board. The tv is working but I'm getting some bleeding that is more seen on red's and white's, mostly on the left side of the screen. The picture is very bright though. Is there adjustments I need to make or do I possibly still have a problem with the YSUS board or maybe the ZSUS board?

Unknown said...

I know this is an old post, but I have a customer who is very adamant about repairing this TV, although I recommended him to purchase something newer. The issue I am having with this TV is that the original failure with it was, in fact, the YSUS Main. After replacing the YSUS Main, everything worked just fine for a few days. However, when powering the TV on, all I get now is a blue led, like the TV is powered on but not displaying a picture. I have replaced EVERY board in this TV, except the replacement YSUS that got the TV working in the first place. Although I replaced the YSUS in the beginning, I still feel that the replacement part was defective causing the issue. I have checked the YSUS and ZSUS to see if they were warm to the touch after powering the TV on: The YSUS was warm but the ZSUS was not, which prompted me to replace the ZSUS, however, even the replacement ZSUS does not get warm either.

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