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Old 05-20-2018, 05:36 PM   #1
Samshell
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Default Samsung PS51E550 Y-Main

Hi guys!

So recently we were watching a movie on our beloved Plasma when there was a pop/bang and the TV went out. I noticed a spark or some such emit from the upper back right of the TV (when viewed from the front).

After a little googling I suspected the Y-Main board had blown to which the Samsung Tech guy confirmed apparently. Since it is well out of warranty I'm hoping with the knowledge and experience of the good folks here I may be able to repair it myself.

I have some reasonable/basic Soldering skills, and I have a Multi-Meter on hand and believe I can follow instructions reasonably well so if anyone is having a slow/boring day I would be glad to be instructed and potentially attempt component level repair on this board.

I have tested the Y-Buffer for shorts as per YouTube tutorial and it seems fine.

Looking forward to any and all responses.
Cheers!
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Old 05-20-2018, 06:31 PM   #2
guix
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Default Re: Samsung PS51E550 Y-Main

Look on the back of Y Main and with multimeter, test for shorts (continuity) on components attached to the heatsinks, if there is a short between the 2 or 3 legs of the same component then remove that component and test it again out of the circuit to confirm it's dead or possibly working ( I use component tester T7 for this, it works quite well, except with components that have all three legs shorted, the tester enters a selftest mode which takes like 30 seconds to complete.. but it confirms that this component is dead ). Repeat for other components until there is no short on the board... If there is like half of these components to replace, it might be a good idea to replace all of them...

My knowledge stops here because I'm exactly in the same boat ^^ with a PS50C530. I'm not sure replacing these components is the only thing to do to repair the board, and the problem might be elsewhere like on my TV apparently because I've changed the Y Main already and it failed instantly, also with a "pak" sound... So now I'm as lost as you are because my Y buffer seems to be OK, voltages (Va and Vs) measured on SMPS (while Y Main disconnected) are also OK...

If you want to check my topic, maybe it can help you: here
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Old 05-20-2018, 08:43 PM   #3
Samshell
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Default Re: Samsung PS51E550 Y-Main

Thanks for the reply guix I appreciate it. I have tested the transistors across all heatsinks to the best of my ability. I get fairly consistent readings across all of the Transistors except the 5 on the largest/longest heatsink closest to the Y-Buffer connectors.

These all read 50~100 when measured from the back and just get the squeal when I do my best to measure them from the top. I have not yet removed any from the board but will do so tomorrow if I have time unless I receive any other info beforehand.

Does anyone know any other generic parts that these may be replaced with that could potentially be sourced here in NZ?

There is a chance I could get hold of a second hand Y-SUS in apparently working condition but seems like a gamble and don't want to risk damaging any other components.

I hope you can resolve your problem guix, sorry I could contribute nothing to your thread.

*Edit: The Transistors on there are 2x 30J127, 2x FGPF-4536 and 1x AUK 91C13 SF10A400H.

Last edited by Samshell; 05-20-2018 at 08:50 PM..
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Old 05-31-2018, 04:00 PM   #4
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Default Re: Samsung PS51E550 Y-Main

Hi guys! I am attaching some images for sake of posteriority. Perhaps these will be useful for someone in the future.

The first is the model and pcb numbers. The second is a photograph of the Y-Main top side, the third is the bottom side and the fourth photo is of the large heatsink with the offending 'fets'?

I also have a question if anyone happens to be reading this. I have purchased a replacement Y-Main that is apparently in good working condition. Are there any precautions I can or should make, or tests that I can carry out prior to installing it to avoid damage to any other components if it is not good, or else a way to test X-Main also as currently I am assuming that only Y-Main was damaged as that was the only thing mentioned by the Samsung Tech.

Also as previously mentioned I have tested the Y-Buffer and it appears to be fine.

Thanks in advance for any assistance!
Attached Images
File Type: jpg Samsung PS51E550 Y-Main 1.JPG (393.6 KB, 11 views)
File Type: jpg Samsung PS51E550 Y-Main 2.JPG (747.9 KB, 9 views)
File Type: jpg Samsung PS51E550 Y-Main 3.JPG (990.3 KB, 11 views)
File Type: jpg Samsung PS51E550 Y-Main 4.JPG (298.6 KB, 13 views)
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Old 05-31-2018, 04:09 PM   #5
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Default Re: Samsung PS51E550 Y-Main

Don't attempt to power up without all the screws done up tightly on the Ysus board or you'll have more problems than you started with.
50~100 ohms, Kohms, Mohms?. If Ohms then I would remove the component and test them out of circuit
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Last edited by dick_barton; 05-31-2018 at 04:11 PM..
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Old 05-31-2018, 05:57 PM   #6
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Default Re: Samsung PS51E550 Y-Main

Test the new board between vs input pin and earth ( at screw hole) to ensure not shorted. I didn't do this recently when eager to fit new board I got but it was shorted after I turned the set on - a problem elsewhere can cause that to happen!!
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Old 05-31-2018, 11:34 PM   #7
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Default Re: Samsung PS51E550 Y-Main

Quote:
Originally Posted by dick_barton View Post
Don't attempt to power up without all the screws done up tightly on the Ysus board or you'll have more problems than you started with.
50~100 ohms, Kohms, Mohms?. If Ohms then I would remove the component and test them out of circuit
Thanks for the advice. Since I purchased the replacement board I'm going to see if it works out before I potentially go further with the failed board. I'll be sure to tighten all the screw as I assume they are creating the ground loop, but as you may have figured I'm a bit of a noob, electronically speaking.

Quote:
Originally Posted by maxvalutech View Post
Test the new board between vs input pin and earth ( at screw hole) to ensure not shorted. I didn't do this recently when eager to fit new board I got but it was shorted after I turned the set on - a problem elsewhere can cause that to happen!!
Hi, thank you also for the helpful advice. Could you be a little more specific please as to what I am testing for? Should I have the board installed and connected to the power board but not the Y-Buffer or completely disconnected. I get strange behavior reading it disconnected, as I first get a reading (sometimes), but then 0L subsequently.
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Old 06-01-2018, 01:14 AM   #8
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Default Re: Samsung PS51E550 Y-Main

You test the board out of set with dmm in diode mode first to see if it beeps (short) then in ohms to see what it reads then - post result but low ohms probable problem.
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Old 06-01-2018, 04:09 PM   #9
Samshell
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Default Re: Samsung PS51E550 Y-Main

Quote:
Originally Posted by maxvalutech View Post
You test the board out of set with dmm in diode mode first to see if it beeps (short) then in ohms to see what it reads then - post result but low ohms probable problem.
Thanks for the reply. Well this is strange (at least to me). When I measure my own blown board in Diode mode it shows a number, does the slightest of squeaks then shuts off. If I measure in 200 ohms i get a reading of 0.03.

When I measure the replacement board in Diode mode I get an initial reading of random numbers then after a second it shows 0L. Subsequent measurements I get 0L and it seems quite random to get a reading. 200 ohm I get nothing.

Perhaps I'm not doing it right, or have been sent a dud.

*Edit. When I test from the solder points on the bottom of my original board i get the tone. When I do so on the replacement board I get the same behavior as before, first a reading in Diode mode and then nothing.

Last edited by Samshell; 06-01-2018 at 04:21 PM..
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Old 06-01-2018, 07:22 PM   #10
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Default Re: Samsung PS51E550 Y-Main

Well I got impatient and tried the board anyway and got a picture so I guess we can consider this solved. Hopefully it lasts. Cheers for the help!
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