Samsung Plasma TV

[Paul Vallandigham]

I repaired analog aircraft radios (mainly module swapping) for the Air Force in the late 1970's, so I am familiar with basic electronics, but have no clue about video. Looked briefly in the theory forum and didn't find anything about general video theory. Also have some limited experience doing upgrades and repairs of desktop computers. Hoping to save some money by repairing our TV myself, if possible. I've looked at other threads, but their symptoms don't quite match.

The TV is a Samsung 64" plasma, model # PN64F5500AFXZA,version # UW01, serial # Z6VY3CBFZ00037A.

Symptoms: Turned on TV, ran normally for a few minutes, then spontaneously powered down & re-booted. Shut down again after a minute or two and stayed off with power LED started cycling 5 double-blinks (is this a troubleshooting code?). This power LED 5 double-blink has been pretty consistent since the first failure. Found that unplugging power cord for a few minutes and then re-plugging resulted in normal operation for variable amounts of time before failure as noted above (power down & 5 double-blinks). Ran the TV this way for about a week, hoping that whatever was causing the problem would fail altogether, rather than intermittently.

Last night, wife was watching TV, looked away, looked at TV again and saw no picture, followed immediately by a single loud pop. She reports she turned the TV off & back on and got sound, but no picture, followed by two more pops.

Based on what I've read on other threads and her description of popping sounds, I was hoping I would find obviously blown capacitors (bulging tops) when I removed the back, but have not found any. What I assume is the main logic board (sound wires going to speakers, ribbon cables going to what I assume are the vertical and horizontal video boards) is showing a flashing green LED. I don't recall the timing of the flashes. Still have sound but no video.

Any ideas for where to start? Also, I have read there is possibly residual high voltage to beware of on some TV's and that leaving it powered down for about a day will eliminate the danger. True? I will post pictures later today so others can guide me about the nomenclature of the various circuit boards.

[dick_barton]

Re: Samsung Plasma TV

Initially check your Va, Vs, Ve, Vsc voltages as given on the label attached to the back of the plasma panel. Popping sounds like maybe some mosfets have possibly blown.
A close inspection of the boards and also for poor/dry solder joints.

Photo's would be useful.

[dskall]

Re: Samsung Plasma TV

Post some good pictures of boards and back of TV. With popping there should be visual clues to where to start. Burnt spots, holes in semiconductors etc. Checking voltage and discharging of high voltage is a must before poking around.

[Paul Vallandigham]

Re: Samsung Plasma TV

OK, shot some pics for reference. Any ideas where to look for test points to get Va, Vs, Ve & Vse readings?

[Paul Vallandigham]

Re: Samsung Plasma TV

Saw no obvious signs of burnt components and none of the typical odors thereof. I assume these voltages are all DC, right? And is there a way to discharge multiple capacitors at once, or must they be shorted individually? Any other components that retain a dangerous charge?

[maxvalutech]

Re: Samsung Plasma TV

Hi this tv is from around 2013 so any info on testing prior to late 2010 probably wont apply. Looking from the back on left you have Y board with buffers attached to screen on the right is the X board similarly attached to screen. Power board is obvious and VS and VA test points are clearly marked on it. The main board with signal inputs also has control/logic incorporated. The tv has a protection circuit which turns the set off when a problem is detected. The power board has a standby dc 5V when switched on at PP and also generates control 12v sound about 18v and Vs about 200v and Va about 65V (correct values should be on a label on rear of panel) at turn on with RC. The powerboard is divided into hot and cold sections with the hot voltage being measured between legs of large caps one probe on each leg and normally 350-400V which on switch off in circuit should dissipate within a few minutes. Vs and Va are needed to power Y and X circuits which generate the "canvas" for the picture sequences which are put together and then erased by control board very quickly of course. You have about 3 seconds to test voltages upon turning this set on so everything needs to be set up in readiness to measure beforehand. Try it all connected first and particularly on Vs test point. The Y and X boards share the high voltage and under the heatsinks will be components likely to blow. Try the Vs test again with the connector to Y disconnected from powerboard. What you are doing is trying to eliminate powerboard as problem and this would be so if no reading with Y on and good reading with Y off but you still only have 3 seconds in each case! It is likely a Y or X problem given the popping and careful removal of these boards for a look under etc will be on the cards. Hope this helps and others with more knowledge will likely tune in when your test results are shown.

[Paul Vallandigham]

Re: Samsung Plasma TV

OK, I get much of what you're saying, but you lost me with a couple of those abbreviations. Can you either explain them or give me a link to a webpage that does?

"The power board has a standby dc 5V when switched on at PP..."

PP = plasma panel? If so, it's not clear to me what you're saying.

"...control 12v sound about 18v and Vs about 200v and Va about 65V (correct values should be on a label on rear of panel) at turn on with RC."

RC = remote control?

And thanks for directing me to the Vs & Va test points on the power board. It's been a few decades since I tore into something this deeply, so wanted to confirm that the "VS" & "VA" printing on the board were Vs & Va. Any guesses where the Ve and Vse test points might be?

The label on the plasma panel indicates the following:

Va = 55
Vs = 217
Ve = 105
Vsc = -198

Lastly, the heat sinks with likely blown components underneath that you are referring to -- are these the black ones on the X & Y boards or the silver-colored ones on the power board?

Thanks again for the tips. I'll be doing some testing in the morning and get back to you with the results.

[maxvalutech]

Re: Samsung Plasma TV

Hi again. PP is power point (wall socket).'RC is right. Voltages relate to control board and audio output etc and will be marked on board near connectors. The black and silver strips are heatsink but the hard to see components are under black by look of it. Pics too small on my phone to get detail but other points to measure should show on boards. Vs is the key though I think.

[Paul Vallandigham]

Re: Samsung Plasma TV

OK. Thanks for the clarification. I'll see what I can find.

[rccrasher65]

Re: Samsung Plasma TV

OK, I get much of what you're saying, but you lost me with a couple of those abbreviations. Can you either explain them or give me a link to a webpage that does?

"The power board has a standby dc 5V when switched on at PP..."

PP = plasma panel? If so, it's not clear to me what you're saying.

"...control 12v sound about 18v and Vs about 200v and Va about 65V (correct values should be on a label on rear of panel) at turn on with RC."

RC = remote control?

And thanks for directing me to the Vs & Va test points on the power board. It's been a few decades since I tore into something this deeply, so wanted to confirm that the "VS" & "VA" printing on the board were Vs & Va. Any guesses where the Ve and Vse test points might be?

The label on the plasma panel indicates the following:

Va = 55
Vs = 217
Ve = 105
Vsc = -198

Lastly, the heat sinks with likely blown components underneath that you are referring to -- are these the black ones on the X & Y boards or the silver-colored ones on the power board?

Thanks again for the tips. I'll be doing some testing in the morning and get back to you with the results.

Ve- located on xmain board. Vsc- located on y-main board. looking from back of tv ymain on extreme left. x=main on right, power supply middle top.

[dskall]

Re: Samsung Plasma TV

I have limited experience with plasma or lcd for that matter. It has been my experience that the y main and y buffers are usual suspects. Those are the boards on the left side. The two long boards (buffers) and the board plugged into them y board. One board takes out the other with catastrophic component failures. Look closely at the 10 chips on the buffer boards for bumps or holes in the tops. If you know how to check components start checking the ones on the heatsinks for shorts. There are several others on the forum that will probably help and much better than I

[Paul Vallandigham]

Re: Samsung Plasma TV

Hi this tv is from around 2013 so any info on testing prior to late 2010 probably wont apply. Looking from the back on left you have Y board with buffers attached to screen on the right is the X board similarly attached to screen. Power board is obvious and VS and VA test points are clearly marked on it. The main board with signal inputs also has control/logic incorporated. The tv has a protection circuit which turns the set off when a problem is detected. The power board has a standby dc 5V when switched on at PP and also generates control 12v sound about 18v and Vs about 200v and Va about 65V (correct values should be on a label on rear of panel) at turn on with RC. The powerboard is divided into hot and cold sections with the hot voltage being measured between legs of large caps one probe on each leg and normally 350-400V which on switch off in circuit should dissipate within a few minutes. Vs and Va are needed to power Y and X circuits which generate the "canvas" for the picture sequences which are put together and then erased by control board very quickly of course. You have about 3 seconds to test voltages upon turning this set on so everything needs to be set up in readiness to measure beforehand. Try it all connected first and particularly on Vs test point. The Y and X boards share the high voltage and under the heatsinks will be components likely to blow. Try the Vs test again with the connector to Y disconnected from powerboard. What you are doing is trying to eliminate powerboard as problem and this would be so if no reading with Y on and good reading with Y off but you still only have 3 seconds in each case! It is likely a Y or X problem given the popping and careful removal of these boards for a look under etc will be on the cards. Hope this helps and others with more knowledge will likely tune in when your test results are shown.

As you reported, got nothing when I waited after initial power up to measure. I had my wife grab the remote so the meter leads were in place on the test points when she turned it on. Va shows 54.8, Vs shows 215, so the power supply seems to be working (voltages dropped to zero within a few seconds, so I assume that's capacitors dissapating after fault detect shutdown). Measurements remained the same whether both X & Y cables were connected, one or the other was disconnected, or both were disconnected. Also got good 15V and 5V coming into the main board.

Still can't locate markings on any board indicating where I can measure Ve or Vsc. Perhaps Samsung uses another abbreviation for these?

Any ideas for what to do next?

[Paul Vallandigham]

Re: Samsung Plasma TV

Ve- located on xmain board. Vsc- located on y-main board. looking from back of tv ymain on extreme left. x=main on right, power supply middle top.

Thanks for the clues, rccrasher65. Looked again and found the following test pads:

On the Y board:

VSCAN (could this be Vsc?)
SVC_YOUT (could this be Vsc?)
SVC_GRND (obviously ground)
SVC_VS
SVC_GRND (same as above)

On both of the two Y buffers:

SVC_OUTL
SVC_OUTH

On the X board:

SVC_GRND
SVC_VS
SVC_VE

The labeling was a little confusing, as it was different than on the power board.

[dick_barton]

Re: Samsung Plasma TV

You need to measure the connector voltages as given on the printed labels on the circuit board.

[Paul Vallandigham]

Re: Samsung Plasma TV

Here's what I got on that connector while the TV was in fault shutdown (no Va or Vs).

[Paul Vallandigham]

Re: Samsung Plasma TV

After locating all test pads, I got the following voltages on initial power up (before fault shutdown):

On Y board:

VSCAN =-208
SVC_YOUT = -187 VERY briefly
SVC_VS = 215

On X board:

SVC_VS = 215
SVC_VE = 107

As there was no SVC_GRND pad on the Y buffers, I decided not to test those voltages in case grounding elsewhere might cause more problems.

[maxvalutech]

Re: Samsung Plasma TV

Well done and looks as if the power board ok but as dickb says check them voltages at final output from the board or at in connector on Y or X if easier. If still coming on within the 3 secs then I would suggest you pull the y for examination - carefully as buffer connections can be tight.

[dick_barton]

Re: Samsung Plasma TV

What about the voltages on the connector at the top left hand corner Va = xx, Vs =xxx

[Paul Vallandigham]

Re: Samsung Plasma TV

That last pic I sent shows the readings I got on that power board connector going to the main board (during fault shutdown). Do I need to test those (and at the power board connector going to the Y & X boards) during that initial 3-second power-up before fault shutdown?

[Paul Vallandigham]

Re: Samsung Plasma TV

What is the voltage at PS_On and VS_ON when in standby and as you attempt to come out of standby?

I'll let you know ASAP.