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Old 04-28-2018, 11:32 AM
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slipstream55 slipstream55 is offline
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Samsung UN55B8500XFXZA Shuts off by itself w/ clicking

Hello, everyone.


My first time on the this Forum but a regular on the AudioKarma forum. I posted this on the AVS forum but no responses yet.


I have a Samsung UN55B8500XFXZA that has the same problem that everyone else seems to have had with this model (and others) ...the panel shuts off by itself during a program and won't turn on/off with the remote. It has to be unplugged from the wall and after a short period of time the blue power LED turns off. Plug the panel back in again and after a setup scan it works for a while. We're past the unplug and wait before turning back on again stage now to get it to work as it won't power on at all other than a brief wink of the blue power on LED.


I have the back cover off and have done a visual inspection of all of the caps on the Power Supply board. No apparent cold solder joints and no bulging/leaking caps. I do get the clicking relay (about 2-3 second interval) when I power the panel ON and continues to click after power is removed about 15 seconds or so before stopping. When I dis-connect the Main Board and apply power, there is no relay clicking. All other connections remain connected to the Power Supply board. This is/was an intermittent issue. After disconnecting all of the connectors on the power supply board and reconnecting them, I powered the panel up and it worked fine until I shut it off. Just the initial power on relay click.


With power off, I'm getting 0.00VDC across all of the yellow caps except for one that is retaining residual voltage of about 10 VDC and verrrry slowly bleads off.

The fix for this problem (99% of the time) has been to replace caps on the Power Supply board. Problem is, nobody has indicated which ones to replace.

My questions:


I have an ESR tester. Can the caps be checked in circuit?
With no visual cue, which caps would I start considering for replacement?


There are 9 small electrolytics spread across the board as well as 5 large black and 11 yellow ones as shown in the attached jpeg.

Any troubleshooting suggestions would be appreciated.


Thanks in advance.
Attached Images
File Type: jpg Board and caps.jpg (110.9 KB, 36 views)
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Old 05-09-2018, 01:04 AM
mgross0 mgross0 is offline
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As no one else has replied, I will be the jerk who tells you to just throw it away. These TV's had issues when new with the power supply, and parts/boards are no longer available. I don't want to discourage you from fixing it as a hobby, but for your daily tv, just replace it. Only this time, buy an LG. They are not perfect, but they contain less 'suck'.
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Old 05-10-2018, 06:38 PM
Kcnelectron Kcnelectron is offline
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There is a fix for it I do not believe its a cap on the power supply , I believe its either a bad main board (costly but available ) or a possible firmware issue . I can look it up in my archives or on samsungs servicer site . I would say first check firmware first its free and then we can go from there ... let me know either way
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Old 05-13-2018, 11:45 PM
6GH8cowboy 6GH8cowboy is offline
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In the world of Laptops, service parts are very limited. Once the warranty expectations are over, replacement parts are auctioned off by the pallet. The manufacturers wash their hands and the next iteration of the product marches on. The parts we find on " the net" are where is/ as is.

In the TV world, pallets of returned tv's and spare warranty parts are like wise auctioned for part cannibalization. A friend of mine has purchased many a pallet and forwarded. Pretty much gone are the days of manufacturer parts support.

Like previously mentioned, just buy a new one or try the minor cost risk of some caps. If not caps, PCBS are not worth the gamble IMHO.
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Old 06-11-2018, 12:15 PM
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slipstream55 slipstream55 is offline
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Thanks for all of your responses.

I am currently in the process of recapping the P/S board as doing this seems to have the highest rate of success for fixing this particular problem on this model and other Samsung flat screens. All of the electrolytics are getting replaced. I saw no bulging/leaking caps during the visual inspection and only one cap (22uF/450V) out of all of them had a high but still within spec ESR value. The rest measured very low ESR.

I have read tons of posts on this problem and the only other failure was an intermittent solder connection on a transistor near the output connector to the Main board that re-flowing the connection fixed. Have not checked this on my P/S board yet but will soon. I am waiting for a 680uF/35V cap to arrive from Mouser. I mis-read/made an assumption that the five small yellow caps were all 1000uF/25V caps. Turns out one was a 680uF/35V cap. I did see where one user ran into the same issue and couldn't find a 680uF cap and instead, installed a 1000uF/25V cap with no ill effects and fixed his flat screen. Not sure I want to do that without knowing it is safe to do so.

I did do a cursory visual inspection of the electrolytic caps on the Main and LED boards but didn't notice any bulging or leaking caps there.

I inherited this Flat Screen from my brother in 2010 pretty much new in box and it has worked flawlessly up until about the beginning of this year when it started doing the random shutdowns and relay clicking. Hence, I thought it worth the time and minimal expense to try and fix.

If this does not correct the problem, I will concede it is time to replace it and yes, with an LG.
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Last edited by slipstream55; 06-20-2018 at 02:25 PM.
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Old 06-20-2018, 02:36 PM
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slipstream55 slipstream55 is offline
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Update:

Got all of the electrolytics swapped out with Panasonic or Nichicon low ESR caps. Did not RTV them in place as was originally done on the board because I wanted to make sure it powered on without issues from the cap replacement. Also, re-flowed two solder connections on two transistors that had visually questionable solder joints. One of the transistors was near the Main Board output connector. Successful powered up. Installed the back cover and ran the panel for three hours last Saturday night. Ran it for one hour Sunday night and two hours on Monday night. Is working fine so far. Time will tell if the cap replacement and re-flowing the transistor solder connections have fixed the shutdown problem.
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