Samsung 50" plasma blank screen

**PlainBill** · 02-03-2012, 07:06 AM

Re: Samsung 50" plasma blank screen

Originally posted by Tweek4

My samsung tv is about 4 years old and has never had a problem - until yesterday.
I decide to move the tv from it's wall mount location to another room on it's stand. I turned off the tv, removed all cables, carefully(with help) took it off the wall, turned it upside down, screwed the stand in position, gently took it to it's new location, connected the cables from sat receiver and DVD and audio receiver, turned on .........no picture at all. No menu screen. No source indication. There is audio and the standby led lights up. The blue logo light lights when turned on and the melodious chime is audible.
I have read Tom66's guide to fixing plasma tv but haven't attempted anything yet. Hopefully it may be a fuse?...
Any ideas?
I have a sodering iron and DMM that I use to DIY my hifi gear, but have never touched a tv.
Cheers
Peter

Yes, I have several. Out of respect to Topcat, I won't express my opinion of someone who won't even mention the model number of the TV.

When you 'turned it upside down' did you place pressure on the face of the TV? The single most likely cause of the failure is you broke the plasma panel.

If you are sure that did not happen, in your next post provide the exact model number and a single picture of the back of the TV (with the back cover removed). Attach the picture using 'Manage Attachments' - below the text entry area.

PlainBill

**Tweek4** · 02-03-2012, 10:28 AM

Re: Samsung 50" plasma blank screen

Samsung PN50A450P1DXZA
No pressure applied to the panel. Upside down-not face down.
Relay(s) clicks when power cord is plugged in. Green LEDs flash for a couple of seconds then goes out.
When power button is pressed, lower left LED flashes continually.
Slight buzzing from (I think) the power supply board-upper center.
Thanks
Peter

Attached Files

**PlainBill** · 02-03-2012, 12:14 PM

Re: Samsung 50" plasma blank screen

I've marked up a picture, indicating significant points.

In the lower right corner is the signal cable from the main board to the logic main board. That caries the video signal. Check to make sure the cable is firmly seated in each connector. The one on the main board appears to be a locking connector. If you don't know hoe to release it, attach a picture. Also, check all poser supply cables.

PlainBill

Attached Files

**Tweek4** · 02-03-2012, 04:13 PM

Re: Samsung 50" plasma blank screen

Thank you, Plainbill.
I have checked every ribbon and wire connector for security, except the the type that carries the video signal. They appear quite fragile and I am not sure how to release them. There is no sign of corrosion anywhere and all seem tight.
All fuses check OK.
I cannot see any signs of capacitor failure or toasty resistors. This is the first time the back has been off and everything very clean and secure.
I'm attaching a picture of the main board-maybe I should check the video signal connectors.
When I power on the tv, there is a momentary, very slight flicker on the screen (twice) when the chimes start and stop.

Peter

Attached Files

**tom66** · 02-03-2012, 04:16 PM

Re: Samsung 50" plasma blank screen

To remove: Lift the latch, remove the cable.

To replace: Insert the cable, close the latch.

**Tweek4** · 02-04-2012, 05:23 AM

Re: Samsung 50" plasma blank screen

All connectors are secure.
Not sure where to go from here-maybe hang it back on the wall!

**PlainBill** · 02-04-2012, 06:24 AM

Re: Samsung 50" plasma blank screen

Originally posted by Tweek4

All connectors are secure.
Not sure where to go from here-maybe hang it back on the wall!

I doubt if that would change anything. It MIGHT be a bad solder joint, but finding it would be a real challenge. One common fallacy is 'Post hoc, ergo propter hoc' (Action A preceded event B, therefore A caused B). If there was no unusual pressure on the panel, the TV wasn't dropped or bumped hard, let's try troubleshooting this as a simple 'No Picture' problem.

Let's try this from two directions. One is I will try to determine if it is possible to put the TV in self test mode. A close up picture of the main logic board will help me with that.

The second is your responsibility. First, you already mentioned fuses. There are ones on the X-Main and Y-Sustain. Check them. Next, on the back of the plasma panel is a white label indicating several voltages. It's clearly visible in the first picture. The power supply outputs that feed the Y-Sustain and X Main should have those outputs identified. Carefully check those voltages with a DMM. Note the voltages - if you are very careless it might be possible to get 400 volts across your body. Try to avoid this.

PlainBill

**Tweek4** · 02-05-2012, 06:58 AM

Re: Samsung 50" plasma blank screen

Many thanks, PlainBill.
I'll post a closeup of the logic board shortly.
Not sure how relevant this is, but this morning, in a dark room, I powered up the tv and the panel is illuminating(I couldn't tell that in daylight). The panel had a very even gray glow.
I have removed all fuses that I could find and they check fine.
I am assuming that the problem is signal issue and not a power issue.
I will check has you advised and be careful with the DMM.
This is probably a dumb thought, but when we carefully carried the tv 20 feet or so to it's new location our hands were all over the buttons that are located on the lower right corner and my initial thought was that some combination of button pushing had locked out the video???
Back to reality.

Peter

**PlainBill** · 02-05-2012, 07:07 AM

Re: Samsung 50" plasma blank screen

Originally posted by Tweek4

Many thanks, PlainBill.
I'll post a closeup of the logic board shortly.
Not sure how relevant this is, but this morning, in a dark room, I powered up the tv and the panel is illuminating(I couldn't tell that in daylight). The panel had a very even gray glow.
I have removed all fuses that I could find and they check fine.
I am assuming that the problem is signal issue and not a power issue.
I will check has you advised and be careful with the DMM.
This is probably a dumb thought, but when we carefully carried the tv 20 feet or so to it's new location our hands were all over the buttons that are located on the lower right corner and my initial thought was that some combination of button pushing had locked out the video???
Back to reality.

Peter

The uniform gray glow could indicate an X-Main problem. I've dealt with the equivalent problem (Z-Sustain) on LG TVs, but I have not had to deal with it on Samsung TVs. On the LG TV a very faint image was visible in the lower right corner.

PlainBill

**Tweek4** · 02-05-2012, 08:48 AM

Re: Samsung 50" plasma blank screen

Here is the closeup of the main logic board.
have yet to voltages(busy finishing my DAC/headphone amp project)

Attached Files

**Tweek4** · 02-05-2012, 10:49 AM

Re: Samsung 50" plasma blank screen

PlainsBill....
Vs measures 205vdc

Va measures 55vdc

Peter

**PlainBill** · 02-05-2012, 11:24 AM

Re: Samsung 50" plasma blank screen

When you are ready to resume troubleshooting, try this. Remove the LVDS cable from the top connector. Place a jumper (such as is used on a hard drive) on pins 1 and 2 of CN2007. Then turn the TV on. If it displays a series of patterns the problem is the main board.

PlainBill

**Tweek4** · 02-05-2012, 12:17 PM

Re: Samsung 50" plasma blank screen

PlainBill

Did that - no change - no patterns

**tom66** · 02-05-2012, 02:28 PM

Re: Samsung 50" plasma blank screen

Do you hear a faint buzzing sound from either board on the left or right of the TV while in operation?

**Tweek4** · 02-05-2012, 04:12 PM

Re: Samsung 50" plasma blank screen

Hi tom66....
Yes - both boards-seems to emanate from the centre of the large heat sink on the left board. Hard to discern on the right board. Both very faint and slightly different pitch.
Peter

**Tweek4** · 02-08-2012, 05:13 AM

Re: Samsung 50" plasma blank screen

Tom66...
Is the buzzing normal?
I disconnected each buffer in turn and saw no change.
Grasping at straws.
Peter

**kc8adu** · 02-08-2012, 07:43 AM

Re: Samsung 50" plasma blank screen

if it worked fine till you reattached the stand is it possible you used the wrong bolts to put the stand on?iirc i saw this on a westinghouse.too long of bolts damaged a board.

**Tweek4** · 02-08-2012, 07:50 AM

Re: Samsung 50" plasma blank screen

Stock screws were used - I thought the same thing initially but on examining the stand bracket inside the tv - plenty of clearance.

**Tweek4** · 02-08-2012, 09:07 AM

Re: Samsung 50" plasma blank screen

For the heck of it, I measured the heat sink temps after 15 minutes of run time.
They were all warm, from 112F on the PS to 102F and 94F on the Y and X(Z) boards.

Samsung 50" plasma blank screen

Samsung 50" plasma blank screen

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