PS43E450A1WXXU Intermittent sound but no picture

[Shotgun25]

Hi all,

I've read quite a few topics on this forum, but since this problem is intermittent I haven't successfully diagnosed it.

The TV is a Samsung 43" Plasma - model PS43E450A1WXXU.

There are no bulging capacitors, most of the time the TV works and the time to picture loss is not constant, but could be heat related.

Previous searching on the internet led him to buy a replacement Logic board but he bought used so it could have the same problem. I fitted it for him and it has intermittently failed since, first occurrence was less than a day later.

I've since obtained this TV permanently from a relative who has replaced this and had it sat around because he didn't want to miss crucial moments of sports games due to picture loss.
He said that it happens completely randomly, regardless of input source (although only used TV tuner and HDMI) and said that most of the time it's after it has been running more than 30 minutes although on one occasion the picture went after 15 seconds of turning it on from cold in the morning.

I have checked some voltages but only while it was working fine but with no source connected. While I have had it I have only made it fail once with the back off but didn't have the TV in a position where I could measure (stood upright and poor lighting in the room it was in).

X-Buffer to Y-Main (I think, position Top Right) Connector CN4003

Pins in the order printed
11 DGND 0
10 OUTL 80V
9 OUTL 80V
8 OUTL 80V
7 DGND 0
6 DGND 0
5 VS 209V
4 VS 209V
3 DGND 0
2 15V 15.19V
1 DGND 0

PSU to X-BUFFER (I think, position Centre Right) Connector CN802

Pins in the order printed
12 VS 209V
11 VS 209V
10 NC 0
9 VA 58V
8 GND 0
7 B15V 15V
6 B5V 5V
5 GND 0
4 VS_ON 3.24V
3 VS_ON 1.34V
2 PS_ON 169.3mV
1 GND 0

I'm open to suggestions for places to check, troubleshooting routines, ways to force it to fail to identify the problematic board/component.

I'm interested in repairing the faulty board if it is possible.
I have bought an 150MHz oscilloscope (Tektronix 2445A) without probes, so I still need to figure out what are the right probes to buy for working on these types of electronics. I figured out I most likely need just passive 10X probes, but I don't know if I need the full 150Mhz rating for this sort of work. Then I will hopefully be able to see failures easily once I know how to probe the high voltage stuff safely after a bit of practice (and maybe guidance from this forum).

After having said all of the above, the following link seems to suggest that the problem board is likely to be Y-Buffer, but my problem is intermittent not permanent so I'm not convinced.
Also having followed the advice on there I have checked the Logic board light flickers 1 time every second so should be deemed good?
When I made it fail the yesterday it was flashing maybe 1 time every 6-10 seconds (I wasn't counting with a time source to hand).

[Shotgun25]

Re: PS43E450A1WXXU Intermittent sound but no picture

Just to confirm, this is not the 2 seconds to black issue covered by budm (i think that was him).

Any advice relating to this TV's random problem?

[Shotgun25]

Re: PS43E450A1WXXU Intermittent sound but no picture

I've just acquired a known working model of this TV, would be interested if there is any quick ways to test what's at fault on the original using a multimeter.
I'm going to swap boards that are easy to remove one by one to try and isolate the faulty part with a view to repair or replacement of that board.
This is now a summer project for me and my boy so any pointers would help teach a 13year old inquisitive mind some skills that I sadly lack.

[dick_barton]

Re: PS43E450A1WXXU Intermittent sound but no picture

I would remove each board in turn and check for poor solder joints very carefully. Use an eye glass if you have one. Make good any joint which looks dull grey or may have a crack around the solder joint.

[Shotgun25]

Re: PS43E450A1WXXU Intermittent sound but no picture

Thanks for the response.

We have got the failing TV to fail after quite a while of watching YouTube on a FireStick through it then after getting bored of waiting and to ensure we could force the YouTube quality we put a laptop to it via HDMI and a 1080p resolution then running the Big Buck Bunny 1080p test video on youtube.
Video referenced https://youtu.be/ZSn3Tvc7jQU
The image failed about 4 minutes in just before the epiphany of how to strike back but we could still hear the sound.

The logic board LED changed from a steady 1 second pulse to a 3-5 seconds on then off for 1 second.

We have swapped the logic board for the one from the newly acquired working TV and couldn't get it to fail but only had about 30 minutes to stress it and it played various HD streams on YouTube in 1080p from the laptop.

We took out the Y-Main? (big board on the left) connected to Y-Sus? (buffer board that wraps around to screen) and couldn't see anything bad on the solder or chips.

I checked the logic board under a microscope, I'll check the Y-Main? under a microscope today when we remove it again.

I was watching a video for the PS43D450 on YouTube (https://www.youtube.com/watch?v=PC1Fo1Huipg) and I'm pretty sure he said that if you replace the Y-Main, you should also replace the Y-Sus.
Are these parts paired?
Or does one cause the other to fail?

[Shotgun25]

Re: PS43E450A1WXXU Intermittent sound but no picture

Well I tried to get the logic board from the bad tv to fail in the good tv and also to get the bad tv to fail with the good logic board but no joy, ran all day with 5 runs of the 1080p big buck bunny followed by some Xbox gaming the lad did for a few hours.

Any tips on encouraging the failure to become apparent sooner?

[dskall]

Re: PS43E450A1WXXU Intermittent sound but no picture

Try some heat or tapping around with something nonmetallic

[Shotgun25]

Re: PS43E450A1WXXU Intermittent sound but no picture

So a hair dryer around the logic board and y-main (left board?) should reduce my waiting times if it is heat related?
Will give it a go tomorrow when we look at it again. I'll get it to fail in it's original condition, then I'll switch the bad logic board to the good TV to get it to fail in there before heating y-main

Thanks

[Shotgun25]

Re: PS43E450A1WXXU Intermittent sound but no picture

I'm back.

I tried to get this to fail with a hair dryer, also the received working TV which is identical to this model doesn't help me via board swapping.

I've tried swapping the logic boards between units and I can't get either to fail after hours of the kids playing XBox on them via HDMI, laptop running a 1080p test from youtube and just leaving them on to get warmer.

I didn't find any bad solder joints on any of the boards and tapping around with my finger and also with the insulated handle of a small screwdriver didn't cause any faults.

I don't want to put the TV into service and have this issue arise as it wouldn't be fair on the family member(s) using it at the time. But because it is so difficult to reproduce and it works 95% of the time, I don't want to throw it away or keep it stood in my computer office or attic doing nothing.

Anyone found any schematics for this model or know of any way of identifying which board to spend my time on?

Looks like I've got a few weeks or months of spending a small amount of time every so often and trying to compare voltages on every pad and maybe even resistance values on each pad to ground.

All I remember from what I saw last time was that the voltages are all present on the Y-Main(?) board on the left but when the screen goes off and the logic board light pulse changes timing, the Y-Main(?) voltages are all missing.

Since they are not present during the fault, I thought the cause would be the logic board not allowing the PSU to send the power to the Y-Main(?), but trying the suspected faulty logic board in the known working TV didn't reproduce the error.

Since I can't reproduce this fault, does anyone have a suggestion for anything I can start testing that might be contributing to this fault from anyone's knowledge?

Thanks for sticking with this thread for so long, much appreciated.