HP PL4272N Plasma has horizontal lines

[kwiksilver]

I've got an HP PL4272N Plasma where there are horizontal lines on every input. I've tried just using one at a time, just component, composite. '

Pictures posted to imgur in an album which shows the models of all of the parts.

http://imgur.com/a/S33OD

Upon visual inspection there doesn't seem to be any damaged ICs. From googling the issue it *may* be the Y-SUS.

Can anyone provide any advice/troubleshooting tips/ideas as to how to fix it?

Thanks so much!

[PlainBill]

Re: HP PL4272N Plasma has horizontal lines

I've got an HP PL4272N Plasma where there are horizontal lines on every input. I've tried just using one at a time, just component, composite. '

Pictures posted to imgur in an album which shows the models of all of the parts.

http://imgur.com/a/S33OD

Upon visual inspection there doesn't seem to be any damaged ICs. From googling the issue it *may* be the Y-SUS.

Can anyone provide any advice/troubleshooting tips/ideas as to how to fix it?

Thanks so much!

Attach the pictures to your post using 'Manage Attachments' - below the text entry area. That way they will be available to others with a problem with the same TV. Also, for a number of reasons (including popups and malware), I do not view pictures saved offsite.

PlainBill

[kwiksilver]

Re: HP PL4272N Plasma has horizontal lines

Images have been attached to this post.

[PlainBill]

Re: HP PL4272N Plasma has horizontal lines

Highly unlikely that is the Y-sus. It MIGHT be the logic main board (behind the signal board), but I would suspect a bad regulator (noisy) on the signal board. Some logic main boards have the ability to be put into self test mode, doing so could eliminate everything except the signal board OR eliminate the signal board.

PlainBill

[kwiksilver]

Re: HP PL4272N Plasma has horizontal lines

I should note there is a loud humming coming from the far left and far right boards on the unit. The humming/buzzing is much louder on the left side.

[tom66]

Re: HP PL4272N Plasma has horizontal lines

The humming is typical of plasma TV sustain boards. They deal with very large currents and these cause inductors to expand and contract, making a buzzing sound.

Do the lines appear to move, or are they stationary?

Possible scenarios:
If they move:
- noisy/faulty regulator (as PlainBill suggests)
- bad cap on Vs or -Vy (potentially others)
- incorrect voltages

If they don't:
- bad control board (possibly bad memory)
- bad main board (test as PlainBill suggests)
- rarely, a bad buffer (but all chips would have to go at once, there are usually 8 - 16 of them, so I'd call it unlikely)
- loose Y drive connector - do the lines appear lit on every second horizontal line, or is the distribution random? I had a Panasonic plasma to repair; if one of the Y drive connectors was slightly loose you'd get an interlaced picture.

[josh1978]

Re: HP PL4272N Plasma has horizontal lines

I have the exact same issue. I disconnected everything from the main logic board and reconnected. Picture looks great for a few seconds and then slowly starts getting the lines back... Sounds like I need a new main logic board, would you guys agree?

[tom66]

Re: HP PL4272N Plasma has horizontal lines

I have the exact same issue. I disconnected everything from the main logic board and reconnected. Picture looks great for a few seconds and then slowly starts getting the lines back... Sounds like I need a new main logic board, would you guys agree?

That sounds more like a power supply problem, perhaps the voltages are drifting out of tolerance?

[josh1978]

Re: HP PL4272N Plasma has horizontal lines

Image of the main logic board

[kwiksilver]

Re: HP PL4272N Plasma has horizontal lines

So he should measure the voltages from the PSU and see how close they are?

[tom66]

Re: HP PL4272N Plasma has horizontal lines

So he should measure the voltages from the PSU and see how close they are?

Yes. The two most important voltages are Vs and Va. They are written on the panel itself.

[kwiksilver]

Re: HP PL4272N Plasma has horizontal lines

The Vs was at 60v and the Va was at 185v which are exactly the specs they need to be according to the printing on the board of the PSU.

I've attached a pic of a board and a close up of an area that looks bad, any thoughts?

[PlainBill]

Re: HP PL4272N Plasma has horizontal lines

The Vs was at 60v and the Va was at 185v which are exactly the specs they need to be according to the printing on the board of the PSU.

I've attached a pic of a board and a close up of an area that looks bad, any thoughts?

At first glance it looks like they designed the board so they could use either of two regulators with incompatible pinouts. The discoloration is from flux.

PlainBill

[kwiksilver]

Re: HP PL4272N Plasma has horizontal lines

It's so odd when the main logic board is completely disconnected and reconnected it works for about 60 seconds and then just starts with the lines.

I can upload a video to youtube if anyone would like to see.

All of the power supply voltages check out, Vs, Va, 12v, 5v, 9v, 3.3v etc