Re: Samsung 50" plasma blank screen
I received a letter from Samsung last week indicating that my tv might qualify for a specific repair under a class action suit proposed settlement brought against Samsung. The suit cites a capacitor failure on the power supply board, I believe and to cut a long story short, the repair guru arrived today and checked the suspect capacitor which turned out to be OK. Installed a new power supply board anyway. He also found a couple of bulging caps on the Y sustain board, did voltage checks, and after close inspection of the display panel found...
Tweek4
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Last Activity: 11-26-2012, 05:35 AM
Joined: 02-03-2012
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Re: Samsung 50" plasma blank screen
Thanks for the help, Tom66.
I still have a hard time believing that this tv, having very few hours on it and zero problems, failed by just moving it 20 feet.
I'll keep an eye on the forum for ideas.
Thanks again
PeterLeave a comment:
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Re: Samsung 50" plasma blank screen
yes
Previously I tried a different logic board.Leave a comment:
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Re: Samsung 50" plasma blank screen
Well- I just received and installed the main board. No change.
Vs and Va voltages are the same as previously measured.
Maybe the SMPS board?
PeterLeave a comment:
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Re: Samsung 50" plasma blank screen
I already tried another logic board- no change.
I think I will swap the main board then.
Thanks, tom66
PeterLeave a comment:
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Re: Samsung 50" plasma blank screen
Further check:
with y and x boards disconnected from the smps, ref Vs=206, Va=56, Vs@x board connector=206, Vs and Va at y board connector=190 and 51.
With x board reconnected, Vs and Va no change.
With both x and y boards reconnected, Vs andVa to y board drop to 186 and 48. Vs to x board no change.
Seems like the smps board is not regulating properly.
Any component checks or replace the smps board?
PeterLeave a comment:
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Re: Samsung 50" plasma blank screen
I just checked again.
Voltage measured on the smps going to X board: Vs=206v, Va= 56v
Going to Y board: Vs=182, Va=48v
If I unplug Y board connector, Vs=190v, Va = 52v
Still looking
PeterLeave a comment:
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Re: Samsung 50" plasma blank screen
Tom66...
My tv differs somewhat from the manual I have been referring to.
The power to buffers E and F come through the Y main board on my tv.
Here's what I found.
Va at the test point = 56v. Vs=205v
Va leaving smps board to Y main= 48v(CN810)
Vs leaving smps board to y main= 182v
Va at the Y main socket end was different every time I measured it. From 80v to 240v. Vs at the same socket was 170v. Double and triple checked.
Va to E buffer= 56v.
E to F buffers = 5v, 8v and 8v(3...Leave a comment:
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Re: Samsung 50" plasma blank screen
I don't have a scope. Just a DMM and soldering iron.
I'll spend some time on it this weekend.
PeterLeave a comment:
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Re: Samsung 50" plasma blank screen
F buffer...Leave a comment:
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Re: Samsung 50" plasma blank screen
Here is a picture of the suspect area of the F buffer, with the aluminum shield removed.
No apparent damage-arcing etc.
Vsc measured -190vdc, normal.
So- I may resolve to remove all the boards in sequence and look for a dry joint.
If this were a hifi project I would be tracing the signal circuits rather than power circuits.
Is it worth checking all the video signal ribbons for continuity?
PeterLeave a comment:
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Re: Samsung 50" plasma blank screen
Thanks, Tom66...
There is no damage evident. Just the warped board picture attached to my post # 43.
Since it is the component side that is touching the aluminum shield, I am not sure that is even a problem. I have placed some plasticine type putty ( that yellow semi-sticky stuff) between the board and the shield to separate them. I'll check the Vsc voltage shortly.
PeterLeave a comment:
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Re: Samsung 50" plasma blank screen
Well, you are correct, the E and F buffers are permanently attached. I removed the aluminum shield to have a close look but I couldn't see any evidence of failure.
One think you may help with - I have been unable to find the test point for the Vsc voltage (-190v). I did find the pot that adjusts the voltage but no pin or solder pad.
There is a resistor adjacent mounted vertically on the Y board that has "vscan" silkscreened next to it.
PeterLeave a comment:
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Re: Samsung 50" plasma blank screen
I had similar thoughts. However the manual is a little confusing, as follows:
The diagram in the manual(photo,actually), shows the cable from the smps board to the main board to be disconnected quite clearly, but the socket number given is the adjacent connection which goes to the logic-main board. I disconnected that one after reconnecting the main board and I read zero volts. So.......???
PeterLeave a comment:
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Re: Samsung 50" plasma blank screen
To elaborate on my previous post, the first step in the manual for troubleshooting no video with audio is to disconnect the cables going between the power supply board(smps)
and y, x and main boards and check if Vs and Va are normal.
First, I disconnected all three boards and Vs and Va measured zero.
Then I reconnected the main board only and Vs and Va measured normal(207v and 56v).
According to the manual the smps board needs to be changed.
Does this sound reasonableLeave a comment:
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Re: Samsung 50" plasma blank screen
Thanks for the help.
I read the manual linked in post#42 and started the checks for no picture, and after the first Vs and Va check, the result indicated to replace the power supply board, then the troubleshooting sequence continues(if not fixed by the new board) to check and replace (possibly) x, y, logic boards. Since I don't have the boards readily available, it could be very drawn out and expensive.
The manual did indicate that the buffer boards E and F (the warped board) are removable, so I may remove them and do a component...Leave a comment:
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Re: Samsung 50" plasma blank screen
What are the symptoms of a failed buffer board- before I attempt to remove it?
PeterLeave a comment:
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Re: Samsung 50" plasma blank screen
Thanks for the link - I'll check it out.
PeterLeave a comment:
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Re: Samsung 50" plasma blank screen
Thanks for the link - I'll check it out.
PeterLeave a comment:
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Re: Samsung 50" plasma blank screen
Thanks. Ronnie
There are quite a few boards on ebay - if I decide to go that route.
I'm grasping at straws right now.
I don't know if this pertinent, but one of the buffer boards is quite warped - see the attached pics and the components are touching the aluminum shield or heat sink.
I noticed it when I removed the bracket that secures the stand.
Peter
Pictures wouldn't upload...Leave a comment:
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