sberri
Member
Last Activity: 07-13-2023, 05:05 AM
Joined: 03-17-2015
Location: gilroy
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Samsung pn50b860y2f smps (BN44-000277a) problem
I have a Samsung pn50b860y2f plasma TV that runs perfectly until the smps board (part # bn44-00277a) warms up. All voltages are dialed in as per the label and are stable until the smps warms up (roughly 5 to 10 minutes after power up) Vs and Va measure a stable 207v and 56v respectively. Once the smps is warm however, the two voltages drop to 182v and 50v and the screen becomes dark and has temporary ghosting/image retetion caused from the drop in Vs and Va voltages. If left on, the TV will display ever darkening/smuged images and will shutdown after 10 to 15 minutes of operation. If left to cool... -
Re: Samsung pn50b860y2f smps board problem
I finally had some free time to troubleshoot this further. I've found that mosfet QS801 is overheating. If I keep it cool by a fan or by freezing it, VS and VA are stable and the picture is wonderful. If cooling is removed, VS and VA begin dropping within a minute or two and my picture quickly turns into the examples in my original post. I've cleaned and reapplied new thermal pads and have tried artic silver thermal paste ( without the pads or course) , neither solves the problem. I've also changed out the MOSFET and the new one overheats...Last edited by sberri; 04-11-2016, 12:29 AM. -
Re: Samsung pn50b860y2f smps board problem
Nick, I've pretty much arrived at the same two conclusions. I've not performed the "wait for magic smoke" test yet because I know I'll end up cooking something else. That's just the kind of luck I have. I'm going to hold off a day or two before resorting to that. Hopefully the TV God himself,Tom66, will chime in with some ideas. I have access to replacement poly and electrolyte caps, I think I'll replace all the caps on the secondary side of the board in the mean time. I have two smps boards left for this set, the one in use...Leave a comment:
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Re: Samsung pn50b860y2f smps board problem
@Nick thank you for the suggestion and insight, but unfortunately, I have already done that with the original X, Y, and their respective buffers as well as their replacements that were taken from from an identical fully functional TV. I wish my 125lb dog hadn't made a chew toy out the smps I removed from the working TV to remedy this entire issue. Before you ask, I had placed a bag of jerky on top of the board and ran to answer the front door. Boomer ate the jerky, its bag, and chewed up the board I guess because it smelled like jerky all...Leave a comment:
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Re: Samsung pn50b860y2f smps board problem
Here are some images of the board....Leave a comment:
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Samsung pn50b860y2f smps board problem
I have a Samsung pn50b860y2f plasma TV that runs perfectly until the smps board (part # bn44-00277a) warms up. All voltages are dialed in as per the label and are stable until the smps warms up (roughly 5 to 10 minutes after power up) Vs and Va measure a stable 207v and 56v respectively. Once the smps is warm however, the two voltages drop to 182v and 50v and the screen become darker and has temporary ghosting/image retetion issues. I assume this is from the drop in Vs and Va voltages. See images for screen shots of image problems. If left on, the TV will display ever darkening/smuged images... -
Re: Samsung pn50b860y2f plasma TV blows A/C line in fuses on power board bn44-00277a
It's taken a while for me to get and install new X, Y, and their buffer boards. Picture is great until tv has warmed up (30 minutes or so). If I open a menu from any source I get a ghost of the menu after exiting. Picture looks fine other than the ghost image of static menu. Any ideas?Leave a comment:
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Re: Samsung pn50b860y2f plasma TV blows A/C line in fuses on power board bn44-00277a
The picture does get better at the no signal screen. It looks like a normal no signal screen. As soon as I feed it a signal, it gets bad again.Last edited by sberri; 04-13-2015, 05:50 AM.Leave a comment:
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Re: Samsung pn50b860y2f plasma TV blows A/C line in fuses on power board bn44-00277a
I finally got the time to test the power board. After finding two bad MOSFETs, I decided to just swap out the board. I adjusted the VS and VA voltages as per the sticker inside the TV. The picture looks great for about five minutes and then becomes awful. I've attached images showing the screen. I also noticed the va an vs voltages drop after the TV is on for a few minutes . Not sure if this is normal behavior
[ATTACH]109721[/ATTACH]
[ATTACH]109722[/ATTACH]
...Last edited by sberri; 04-12-2015, 07:55 PM.Leave a comment:
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Re: Samsung pn50b860y2f plasma TV blows A/C line in fuses on power board bn44-00277a
Thank you for the quick response. Is it best to remove them from the board to test them?Leave a comment:
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Samsung pn50b860y2f plasma TV blows A/C line in fuses on power board bn44-00277a
my samsung pn50b860 shut off during an all day movie marathon last week. No standby led, no picture, no sound, no "clicking noises".....it was completely dead. I removed the back and discovered the two fuses on the A/C input side of the power board (part# bn44-00277a) were blown. I performed a visual inspection for bad capacitors as well as any other obviously bad components and everything looked okay. After replacing the bad fuses with identically rated ceramic fuses, I plugged the TV in. It attempted to power itself on and immediately blew both fuses again. Just for giggles, I repeated... -
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