Samsung HPT5054X powers on, but only shows a few lines of distorted video

[fuxxy]

Samsung HPT5054X

Unit powers on, plays the startup melody.

I get *some* output from the panel with no sources plugged in. Pressing menu, volume, etc changes the display slightly.


I'm thinking logic board? I guess the first step is to short the jumpers on the TCON and see if the test patterns work?

[tom66]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

I'm going for X-main.

[fuxxy]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

Is there a method of testing the x main? Or just replace and see?

[tom66]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

You need an oscilloscope to test it. You can make some very basic tests with just a DMM, but not many tests.

[fuxxy]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

Tested VCC and VS going to the X-main, all were within 1V of the spec listed on the panel.

There was also a test point for Ve on the X-Main, that was within spec also.

On a further note, it does appear that the slight output I'm getting on the panel is almost directly where the ribbons from the X-main enter the panel.

I pulled the X-Main, there do not appear to be any physical issues with the board. Is there anything else I can do? I could simply replace the board and see what happens, it appears the X-Main is fairly cheap; $30 USD on eBay.

I would prefer to isolate the problem before blindly buying boards :-]

[tom66]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

There's a bank of 5 or 6 big red caps on the X-main usually, I think these are some of them on the left.

https://www.badcaps.net/forum/attach...8&d=1367132656

Test the voltage on one of the. It should be about the same as the similar red caps on the Y-main, and around 60 to 135V.

[fuxxy]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

For claritys sake - were talking about the odd shaped red blocks, not the green electrolytics, correct?

[tom66]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

Yes.

[fuxxy]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

on both mains, the negative side of the big red caps are connected directly to ground.

Positive side of red caps on X-Main: 101.9 VDC
Positive side of red caps on Y-Main: 72.0 VDC

[tom66]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

So, they should be around the same as each other, I would suggest an X-main fault is likely.

[fuxxy]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

hmm, sounds good then, I'll get one on the way and report back!

[fuxxy]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

Just recieved the new X-main board, installed, and tested (and adjusted) voltages for VS and Ve before plugging in the ribbon cables..

AND.....

Still no dice. Exibiting same problem as before, in exactly the same place.

Just to be sure, I tested voltages listed on the sticker on the panel.

Vs - 207
Va - 63.1
Vsc - couldn't find
Ve - 93.8

Red caps on X-Main - 101.7
Red caps on Y-Main - 72.3

[tom66]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

In which case, here comes the point where you need a scope.

Read through this read. The OP went through multiple X-mains only to discover the fault was a cracked resistor on the control board, which wasn't sending the right signals to the X-main.

https://www.badcaps.net/forum/showthread.php?t=24872

[fuxxy]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

Excellent, I'll see if I can find a scope. In the meantime, I can pull the control board and follow the instructions in some of his tests.

[fuxxy]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

Update:
I shorted pins 5 and 6 on the control board, to put the display into a test pattern. The test pattern was visible through the 'lit' areas of the display, but the 'lit' areas did not change location. It appears it's not a logic board fault. I was not able to find XS and XG test points on the control board.

I did, however, find a control board on ebay for $15. It came out of a Samsung HPT-5064, but all markings on the board are the same.

I've had no luck finding someone around Baytown or Houston with a scope.

[awyatt2]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

look closely at the y-buffers a common failure on these sets. screen will prime but no video in these areas.

[fuxxy]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

I can pull the Y-Main and take some closeup pics, but I did a once-over last time I had the back off, and nothing looked out of the ordinary. No bulged caps, no burnt marks, no odd smells...

Let me get back from eating with the wife, I'll pull the board, and take some macro's.

EDIT: Wait, you're talking about the boards running along the bottom of the display?

[tw2005]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

Y buffers are the 2 boards LHS attached to the Ymain. Common failure is shorted buffer boards( usually the top one) and also shorted FETs Ymain (88N30W) can have other parts failed , fuses blown. Visual inspections don't always reveal much, grab a meter and bell them out for shorts.

I think the bottom buffer boards are known as E & F buffers, I don't think you need to mess with them. If you do, don't run the panel without that long aluminium heatsink mounted and don't spike them with residual power from PSU if you disconnect the power cable for them.

I've done both, cooked and blew the COF ICs and that's game over for the panel.

[fuxxy]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

Just pulled the Ymain, took LOADS of pics. Visual inspection I found a bulged capacitor, C5709, need to pull it to see what value it is if I have one on hand.

In laymans' terms, you're saying to pull the boards and check all the FET's for shorts, gotcha.

However, not quite following you about the pulling power and spiking the buffers with voltage....

EDIT.
Pulled both the buffers on the left side of the panel (looking at the back of the panel)
No FET's on the buffers, but tested all three big white connectors (the ones that go the panel) to ground, no shorts. Mabye you meant the 'supply' side?
Pulling C5709 as we speak

[fuxxy]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

F5700 is blown. (on Ymain)