Yes I know a new TV is cheap these days but I don't feel i've had my moneys worth from the current one!
Its a 2007 Samsung 50" plasma.
It has history - 5 years ago a buffer IC & Y-Sus failed - so i fixed it.
Now its gone again, same symptoms of sound, no picture, Y-SUS LED on.
I've removed the offending buffer IC's on the top buffer board so I can confirm the Y-sus is fixed before wasting new buffer IC's and I have replaced the failed FET on the Y-SUS, all 3 caps that come in a service kit, and checked the fuses. Main PSU rails all appear good....
mph8783
Member
Last Activity: 04-14-2020, 11:41 AM
Joined: 05-16-2013
Location: Gloucestershire
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Samsung Plasma TV, display primed, no picture
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Re: samsung 50" plasma, no picture, no obvious short or blown fuse.
There can be several causes of the fault, if you think it is the same as I had the you should do three things:
1) buy a standard repair kit for your y-sus board. eBay has them, just search for your y-sus board part no.
2) check for shorts on the buffer boards (youtube has info) and buy however many buffer ic's you need. If you haven't replaced fine pitch smd components before you may want to buy a whole board.
Don't power up tv with repaired y-sus with possible faulty buffer board attached,... -
Re: samsung 50" plasma, no picture, no obvious short or blown fuse.
You can see it all in the photos I posted at the start of this thread. I have put the back cover on again now.
I was wondering if it could be VSet + Va = Vs as that works out about right (173V).
I also have a theory that as the caps age, they cause ripple and spikes to find their way to the buffer IC's which blow, then take out the Y-Sus. Therefore if when the panel starts to show higher levels of noise and sparkle on the blacks (which I had for the last couple of months) the caps are...Leave a comment:
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Re: samsung 50" plasma, no picture, no obvious short or blown fuse.
It doesn't list one and there are no obvious signs of lost pixels.Leave a comment:
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Re: samsung 50" plasma, no picture, no obvious short or blown fuse.
Problem solved!
While testing I had only put the Y-Sus PCB in with one screw (to ensure it had a ground).
It appears that it needs more than one - in particular the one in the top left by the VSet circuit.
The TV now works - and VSet has settled at around 110V w.r.t. chassis. Unless anybody thinks this is a problem I will leave VSet as it is.
The general picture quality has also improved from before the failure, less noise and better blacks - clearly some...Leave a comment:
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Re: samsung 50" plasma, no picture, no obvious short or blown fuse.
VScan is -189V (OK)
Va is 63V (OK)
VSet very briefly starts at 189V, then drops to around 110V - What shoud it be?
VSet also appears to vary a little depending on the picture.Leave a comment:
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Re: samsung 50" plasma, no picture, no obvious short or blown fuse.
Some progress...
The TV is capable of working - it just shuts down the Y-Sus after a period of time.
The time period is 2 seconds - i.e. as soon as it tries to drive a picture and not just black most of the time.
However I have had it working for a few minutes before it shut down.
I have also discovered that by disconnecting any two of the Y buffer flexi's to the panel it will stay on, or even the x-sus board (obvioulsy very ghostly picture then).
...Leave a comment:
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Re: samsung 50" plasma, no picture, no obvious short or blown fuse.
It had a source plugged in.
Should the led on the y-sus be on or off during normal operation?Leave a comment:
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Re: samsung 50" plasma, no picture, no obvious short or blown fuse.
Ok, so I have replaced the 2 blown FET's plus the 4 others in parrallel and driving the blown ones. I have also replaced the top buffer IC on the top buffer board.
The TV now switches on and the screen comes to life, even showing the channel number OSD.
But after a couple of seconds the screen shuts off, but sound continues.
Is this likely to be a bad cap I haven't found or something else?Leave a comment:
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Re: samsung 50" plasma, no picture, no obvious short or blown fuse.
looks like it is a couple of the FET's on the -Vsc side of things. Not sure why I didn't catch on the first pass (must have been half asleep!).
It looks like they are not switched in initially but when they are the switch mode supply on the Y-Main board shuts down protecting things.
Interestingly when power to the TV is then switched off the switch mode supply comes back up again and holds it's 19V rail for about 20 seconds!Leave a comment:
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Re: samsung 50" plasma, no picture, no obvious short or blown fuse.
Yes - it is OK.Leave a comment:
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Re: samsung 50" plasma, no picture, no obvious short or blown fuse.
looks like the small switch mode PSU on the Y-Main card (bottom right below heatsink) isn't starting up. It appears to take the 200V and convert to something under 25V (i'll guess at 24V) for all the power drive stuff (it supplies the 7805 and also a 7815) . Ive replaced the associated electrolytics, but still no luck. Thinking it is eaither an opto-coupler or the MR4710 control IC (is there a non chineese equivelent that is easy to obtain?)
I have also noted that the power LED on the front of...Leave a comment:
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Re: samsung 50" plasma, no picture, no obvious short or blown fuse.
I have just made some progress!
It appears that that the iCoupler (digital opto-coupler) U5704 on the Y-Main board does not have any power on its secondary side.
I assume that this is the link from the logic board control signals to the power electronics, so no control = no drive = no picture.
It looks like it is powered by a 7805 reg - which also has no power, but the +15V Vcc is being supplied to the board.
So hopefully it is just a case of tracing the route...Leave a comment:
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Re: samsung 50" plasma, no picture, no obvious short or blown fuse.
Board Info and Pictures
[URL="https://www.badcaps.net/forum/attachment.php?attachmentid=64058&stc=1&d=1368802328"]Overview of whole TV[/URL]
[URL="https://www.badcaps.net/forum/attachment.php?attachmentid=64059&stc=1&d=1368802328"]PSU Board[/URL]
[URL="https://www.badcaps.net/forum/attachment.php?attachmentid=64061&stc=1&d=1368802328"]Y-Main Board (LJ41-05120A)[/URL]
[URL="https://www.badcaps.net/forum/attachment.php?attachmentid=64060&stc=1&d=1368802328"]X-Main...Leave a comment:
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Re: A guide to fixing/troubleshooting some common plasma TV problems
Ok, new thread is here
[URL="https://www.badcaps.net/forum/showthread.php?t=28761"]https://www.badcaps.net/forum/showthread.php?t=28761[/URL]Re: A guide to fixing/troubleshooting some common plasma TV problems
Ok, new thread is here
[URL="https://www.badcaps.net/forum/showthread.php?t=28761"]https://www.badcaps.net/forum/showthread.php?t=28761[/URL]Leave a comment:
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samsung 50" plasma, no picture, no obvious short or blown fuse.
Hi,
This is a new thread for my specific problem of no picture, and no obvious short, originally started in [URL="https://www.badcaps.net/forum/showthread.php?t=18542"]https://www.badcaps.net/forum/showthread.php?t=18542[/URL].
I'm struggeling to narrow down the fault with my samsung 50" plasma - and any help is appreciated!.
It is a PS50C96HDX/XEU built in 2007.
I was sat watching it when all of a sudden the picture disappeared. There was no bang, smoke or anything else and the TV sound and remote continued to function.... -
Re: A guide to fixing/troubleshooting some common plasma TV problems
Nope, no pink. Just like somebody had unplugged the video source(or psu), but as there is now not even a glow or snow I was suspecting y or x drives rather than logic board.Leave a comment:
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Re: A guide to fixing/troubleshooting some common plasma TV problems
It didn't go off cleanly like when you power off but deteriorated over just 1 or 2 frames and has been black ever since.Leave a comment:
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Re: A guide to fixing/troubleshooting some common plasma TV problems
Hi,
I'm struggeling to narrow down the fault with my samsung 50" plasma - and any help is appreciated!.
It is a PS50C96HDX/XEU built in 2007.
I was sat watching it when all of a sudden the picture disappeared. There was no bang, smoke or anything else and the TV sound and remote continued to function.
The way the picture went off was more like the broadcasters satallite link failed but alas it was the TV.
I have checked all PSU rails (except...Leave a comment:
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