LG 50" Plasma (50PS60) Troubleshooting


	FORUM HOME	SEARCH POSTS	WHO'S ONLINE	LOG IN	RULES F.A.Q.

TV Forums: TV Equipment: TV Repair Forum:
LG 50" Plasma (50PS60) Troubleshooting

Print Thread

fierofan8488
New User

Aug 14, 2012, 12:51 PM

Post #1 of 16 (14556 views)
Shortcut

LG 50" Plasma (50PS60) Troubleshooting	Can't Post

Hey guys, I'm having some trouble with this LG 50" plasma I bought almost exactly 3 years ago. I managed to find the service and training manual for it and was hoping to do the troubleshooting myself and learn a little about these newer flat screen tv's in the process. What happen is that a couple weeks ago after turning off and back on the screen went super bright white and almost looks "snowy". Sometimes I can leave the tv set off for a few hours and turn on and its fine, and its fine if I leave it on all the time but as soon as it warms up and I power cycle it, it goes back to super bright screen. Its like the brightness is set way above its highest setting. I should also note that if its left on when the screen is bright, it gets super hot (too hot to even touch). It also will only turn on for a maximum of 10 seconds and turns back off most of the time.

That being said, I took the tv apart and tested the "AC_DET" pin which should read 5v when powered on. It reads about 4.3v which is why the set powers back off within 10 seconds. I'm also measuring low on some of the power supply pins. I believe VS=185v when it should read 195v. I'm not sure if the power supply is bad or if one of the other boards (ie. Y-SUS or Z-SUS etc.) is pulling too much current. I've yet to check the power supply board with the 2-100W bulb trick. That is next on the list.

Anyone here have experience in TV troubleshooting or where to start troubleshooting on a typical power supply of this type? I've did some quick checks on some of the components and nothing really sticks out to me. Is there a common issue with power supplies that I can check such as the bridge rectifiers or power mosfets? I'd really like to try to pinpoint the problem rather than just replace the whole board. Will be good experience for me for sure.

Thanks for any help!
FF

Ron.M
Veteran

Aug 14, 2012, 6:04 PM

Post #2 of 16 (14526 views)
Shortcut

Re: [fierofan8488] LG 50" Plasma (50PS60) Troubleshooting [In reply to]	Can't Post

fierofan8488;.....

I do not work on your type of TVs...
Some friendly advice is needed.....
"unclegg" has been banned a few times already & is on his way out again...
He is pushing a website that will charge you cash money to try & help you...
Please wait for one of our fine qualified techs to come along & help you for FREE !!!

unclegg;
You have been warned in the past...
You have been banned in the past...
You are now trespassing illegally...
If you post the fletcher website just one more time , all hell will break loose on you...
Think I'm kidding ???
TRY me !!!!

Quote

A solution for this problem can be found HERE!

Kiddies , IF you want to PAY for questionable advice , go here at your own risk !!!!...
IF you want EXCELLENT FREE advice , stay HERE !!!!

Later...Ron.M... Cool

...
Veteran & Retired TV technician

74f100
Enthusiast

Aug 15, 2012, 2:32 AM

Post #3 of 16 (14517 views)
Shortcut

Re: [fierofan8488] LG 50" Plasma (50PS60) Troubleshooting [In reply to]	Can't Post

I've never seen one do that....could you post a picture of the "over bright" screen?

I'll look this up on LG the next couple days,,,,until then definitely load the power supply and monitor VS. It usually only goes low if either the panel or one of the sustains is pulling too much current. This will tell you if the supply is ok....sorry really pushed on time tonight, but I'll check back tomorrow.

Good luck,
Jim
HDMI not working

fierofan8488
New User

Aug 15, 2012, 1:15 PM

Post #4 of 16 (14512 views)
Shortcut

Re: [74f100] LG 50" Plasma (50PS60) Troubleshooting [In reply to]	Can't Post

Maybe I'm not describing the problem well enough. I built the bulb test circuit last night so I will test the supply tonight hopefully. I will definately get a picture uploaded. Thank you for the help!

74f100
Enthusiast

Aug 15, 2012, 9:13 PM

Post #5 of 16 (14506 views)
Shortcut

Re: [fierofan8488] LG 50" Plasma (50PS60) Troubleshooting [In reply to]	Can't Post

I'm assuming you have a meter.

If it is able to test resistance, you could test the Y and Z sustains for shorts to ground.
HDMI not working

fierofan8488
New User

Aug 17, 2012, 9:41 PM

Post #6 of 16 (14484 views)
Shortcut

Re: [74f100] LG 50" Plasma (50PS60) Troubleshooting [In reply to]	Can't Post

Well I finally was able to take a few pictures. One is screen while tv is malfunctioning and the other is during normal operation. Thoughts?

I will try to finally get a chance to test power supply today. I will also check for shorts on the Y & Z sus boards.

74f100
Enthusiast

Aug 17, 2012, 10:46 PM

Post #7 of 16 (14478 views)
Shortcut

Re: [fierofan8488] LG 50" Plasma (50PS60) Troubleshooting [In reply to]	Can't Post

That almost looks more like signal interference.

Does VS change under each condition?
HDMI not working

fierofan8488
New User

Aug 18, 2012, 1:24 AM

Post #8 of 16 (14475 views)
Shortcut

Re: [74f100] LG 50" Plasma (50PS60) Troubleshooting [In reply to]	Can't Post

It does almost look like interference, however, those pics are actually of the internal menu and not of an external signal. All external sources do the same thing and most of the time the tv will shut down within the 10 second window because ac_det is below the ~4.3v threshold when normally it should read 5v. VS is good when tv is cold and operating normal, VA/VS/AC_Det all go low when it malfunctions. I just need to do the bulb test and make sure the power supply is ok. Even if it does turn out to be the SMPS, I hate to buy the whole board when I'm sure its something simple like a cap or regulator etc. I was hoping this was a relatively common problem and by the pics someone would jump in and say "yep def. power supply". Lol, I couldn't get that lucky eh..

74f100
Enthusiast

Aug 18, 2012, 5:50 PM

Post #9 of 16 (14462 views)
Shortcut

Re: [fierofan8488] LG 50" Plasma (50PS60) Troubleshooting [In reply to]	Can't Post

After seeing the pics I would be less likely to suspect the smps. But still do the tests to make sure.
HDMI not working

fierofan8488
New User

Aug 23, 2012, 12:43 AM

Post #10 of 16 (14429 views)
Shortcut

Re: [74f100] LG 50" Plasma (50PS60) Troubleshooting [In reply to]	Can't Post

Well I did some more tests on the smps and z-sus boards and I'm pretty sure its not the smps. Loading the smps with 2 150W light bulbs and even loading m5v line and she holds steady. Only thing that makes me suspicious about the smps still is the fact i'm only measuring around 4.4v on the AC_Det line when it should read 5v.

I think the problem may be coming from the Y-sus board. When I plug in the Y-sus to the smps I get a bunch of noise on the 5v line and the 17v line. No noise when Y-sus is unplugged. Any Ideas what to check on Y-sus board?

74f100
Enthusiast

Aug 23, 2012, 2:47 AM

Post #11 of 16 (14427 views)
Shortcut

Re: [fierofan8488] LG 50" Plasma (50PS60) Troubleshooting [In reply to]	Can't Post

Check the main drive transistors. Also check the connections between the Y-Sus and the buffers. Then the ribbon cables connected to the buffers.
HDMI not working

fierofan8488
New User

Sep 3, 2012, 2:54 PM

Post #12 of 16 (14366 views)
Shortcut

Re: [74f100] LG 50" Plasma (50PS60) Troubleshooting [In reply to]	Can't Post

Just an update. I was wrong when I said it was y-sus. It turns out that when I check transistors on y-sus and z-sus I found that one did have a short on z-sus board (Q15) and z bias voltage read same as VS (195v) voltage when it should have been around 97v. I assume that the z-sus board was actually the board pulling too much current since it gets its 18v from the y-sus board. I did some research on the z-sus board's part # and sure enough I found a repair kit for this exact board that includes Q15 and associated resistors and components. Ebay has several kits for this board too (EBR55360601). I tested all related parts and found that Q15 was the only bad component and ordered one from digikey (51N25). After installing new mosfet I got very low z bias so I did some checking and once again found short in Q15 to Gnd. Come to find out the new mosfet had its gate tied to its metal backing and when installing and attaching to its heatsink it shorted out the remaining components in the z bias circuit, sigh. Long shory short, now I'm waiting on the 10 ohm 5 watt resistor from digikey. Hopefully that will get this tv working.

Thank you 74f100 for the tips. I hope this thread helps someone some day :).

QBAelectric
New User

Mar 19, 2014, 10:33 PM

Post #13 of 16 (11431 views)
Shortcut

Re: [fierofan8488] LG 50" Plasma (50PS60) Troubleshooting [In reply to]	Can't Post

Hi I came across you thread at the forum
I got the same issue withe the TV
Did you manage to fix it?

garfield
New User

Jun 15, 2014, 3:54 AM

Post #14 of 16 (10568 views)
Shortcut

Re: [QBAelectric] LG 50" Plasma (50PS60) Troubleshooting [In reply to]	Can't Post

Exactly the same problem with my tv. If I unplug it and let it sit overnight, then some times on next day, it works fine but if I turn it off and turn it back on, then this problem reappears. When this super bright picture shows up (and it shows the same static image from a cartoon channel as if it is embedded in TV's memory - could be that the channel logo is burned in and shows up when picture is superbright), the TV shuts off within 10 sec. If I disconnect ZSUS board, TV stays on but picture is very dim and sort of reddish.

What could it be that gets reset when TV is unplugged for a period of time?

Is there any way that I can make sure that it is ZSUS board that's bad?

xgc12
User

Jun 15, 2014, 1:04 PM

Post #15 of 16 (10558 views)
Shortcut

Re: [garfield] LG 50" Plasma (50PS60) Troubleshooting [In reply to]	Can't Post

The transistor(s) cools back down thats the reset and what makes the picture back to normal.

If you feel comfortable using a multimeter (check voltages) or if you have a temp gun you could check the temperature on the heat sinks and see which component(s) are failing.

Owner Atlantic Audio & Video
www.atlanticav.net
www.facebook.com/atlanticav

garfield
New User

Jun 15, 2014, 9:39 PM

Post #16 of 16 (10540 views)
Shortcut

Re: [xgc12] LG 50" Plasma (50PS60) Troubleshooting [In reply to]	Can't Post

Thanks for your reply.

When I check voltage, what should I look for? If anyone can suggest points on the board where I should check voltage to figure out which component or board is dead, I'll really appreciate it. Thanks.

Print Thread

Search for (options)

- Page loaded in: 0.13 s on (CGI/1.1)