Need help with faulty PSU board for LG Plasma TV

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snakebite
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likely one or more shorted igbt’s.
look at the y buffer chips for burns or holes.thats the 2 green boards left of ysus.
if none found its a good risk to buy a ysus.
or you can get a parts kit and rebuild yours.

kuoh
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I would bet it’s the YSUS, had a 50” LG plasma go out like that. It started with very intermittent pop and momentary screen dim, but eventually progressed to a black screen with sound. Bought a “new” YSUS on Ebay, but got a well used one which still worked for another couple of years of heavy use. Just gotta be very careful not to press on the ribbon cables from the buffer boards to the screen when installing the new YSUS board.

KuoH

snakebite wrote:
if none found its a good risk to buy a ysus. or you can get a parts kit and rebuild yours.
klrman
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snakebite wrote:
likely one or more shorted igbt's. look at the y buffer chips for burns or holes.thats the 2 green boards left of ysus. if none found its a good risk to buy a ysus. or you can get a parts kit and rebuild yours.

 

Thanks for the help again.  Had a look  yesterday at the y buffer chips and didn't see anything, but tomorrow I'm over there again and will use my trusty flashlight and a magnifying glass and have a another good look just in case.  If I set my DMM to continuity, can I a do a test on the y-buffer chips whilst the board is still connected to the tv or would I have to pull it? 

klrman
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kuoh wrote:
I would bet it's the YSUS, had a 50" LG plasma go out like that. It started with very intermittent pop and momentary screen dim, but eventually progressed to a black screen with sound. Bought a "new" YSUS on Ebay, but got a well used one which still worked for another couple of years of heavy use. Just gotta be very careful not to press on the ribbon cables from the buffer boards to the screen when installing the new YSUS board. KuoH
snakebite wrote:
if none found its a good risk to buy a ysus. or you can get a parts kit and rebuild yours.

 

Ours was a little different.  Just one pop and then the tv shut down and every time we tried to turn it on it would shut off again.

WarHawk-AVG
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http://www.tomshardware.com/answers/id-2260303/flat-screen-turns-turns-b...

Quote:
ElectronicMasterEngineer said: Its likely your flat screen has a cold cathode florescent backlight (CCFL). Unfortunately these are consumable devices and eventually burn out. The reason why it works for a second or two is because the controller chip will ignite the backlight and measure its current draw. As the tube ages it draws more current. If the current is too high the backlight is shutdown to prevent overheating. Unfortunately this isn’t an easy fix, you need to disassemble the lcd panel inside the plastic casing and replace the backlight tube. From experience of doing this fix, I would recommend that you buy a whole monitor and scrap your faulty one.

What model TV is it…might be able to find the cold cathode tube on ebay or something
https://www.ccflwarehouse.com/

Speed4goal
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kennybobby wrote:
@Warhawk

How rude of you to come blasting in here without reading the title or any of this thread before posting. Please delete your useless post and then i’ll delete this one.

Maybe he thinks plasma is a form of LCD.
It’s really ashamed manufactures stopped producing plasmas. I love my 2014 Panasonic plasma TV. The general public wants cheap TVs though. And 300 for a 50 inch Vs 600 for a plasma killed them. I think there’s one company that still makes a few

2/9 Fox Co (2009-2015) Semper Fi 0311/0331 Rifleman/Machine Gunner
Blf has changed a lot since I've been here. Lots of snow flakes and easily offended over nothing. When the forum use to be great and people joked around and could take a joke. It's a forum it's not that serious. Let's make BLF great again!

Lightbringer
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Wow. All these negative waves…

09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

WarHawk-AVG
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Apologies..didn’t mean to come off as rude or condescending

Googling LG plasma turns off comes up with alot of different fixes, maybe this will help

https://www.youtube.com/watch?v=IWq4uBFhSjQ

kuoh
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There’s something to be said about the size and weight of LCDs vs plasmas well. My 50” plasma has been in storage ever since I moved over 2 years ago. The original box it was packed back in won’t even fit in my car and requires 2 people to move as well as unbox and setup the TV. When my “temporary” 42” LCD died, rather than haul the plasma out of storage, it was easier to buy a new 55” slim LCD that fit in the car with the box and set it up singlehandedly.

KuoH

Speed4goal wrote:
It’s really ashamed manufactures stopped producing plasmas. I love my 2014 Panasonic plasma TV. The general public wants cheap TVs though.
kuoh
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I think the point was about understanding more about the topic before offering advice. What you posted was like someone asking to troubleshoot an LED driver and getting a response like Maglights are notorious for burning out bulbs, did you check for a spare bulb in the tail cap. It was not at all related to the technology or problem, but the responses could’ve been less harsh.

KuoH

WarHawk-AVG wrote:
Apologies..didn’t mean to come off as rude or condescending

Googling LG plasma turns off comes up with alot of different fixes, maybe this will help

WarHawk-AVG
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kuoh wrote:
I think the point was about understanding more about the topic before offering advice. What you posted was like someone asking to troubleshoot an LED driver and getting a response like Maglights are notorious for burning out bulbs, did you check for a spare bulb in the tail cap. It was not at all related to the technology or problem, but the responses could’ve been less harsh.

KuoH

WarHawk-AVG wrote:
Apologies..didn’t mean to come off as rude or condescending

Googling LG plasma turns off comes up with alot of different fixes, maybe this will help


No problem…I messed up…apologized for it
Was running empty after a 20+ hr day and was ready for bedtime (skimming thru and not paying attention)

If that is the harshest rebuke for making an ass out of myself I ever get, I will consider myself blessed Smile

klrman
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20+ hr days always make me snappy.  Easy to understand!

hiuintahs
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Back in the 90’s I repaired a lot of VGA monitors. Most of them I did not have schematics…….(simply too many different brands). The problems were similar. If no schematic available this is what I would do:

1) Check the internet with model number to see if anyone has posted any info on a similar problem. If one person has a particular problem is means others probably are too. See if anyone is talking about it.

2) Check for bad capacitors. Have to use an ESR (effective series resistance) meter. I never worry about checking capacitance. It’s the ESR that is the issue. Most of the time you can check ESR in circuit without removing the capacitor. Only in situations where the capacitor is in parallel with a low impedance item like an inductor do you get a false reading……..but that reading will make it look good. But if you get a bad reading in circuit, then the cap is definitely bad. The electrolytic solution dries out over time and generates a series resistance to the capacitance. If there is a lot of ripple current and filtering going on with that cap, then the added resistance increases the power that will be dissipated by the capacitor and that can cause the cap to get hot and bulge. The ESR problem tends to show up with the higher voltage caps and the bigger value ones. Those are the ones I check first.

3) Bad caps can also cause a power semiconductor like a mosfet, power diode, or other heat-sinked semiconductor associated with that cap’s circuitry to go bad. If after replacing a bad cap and it still doesn’t work, then need to look at the power semiconductors. Mostly look for shorts with DMM.

4) Bad solder joints occur over time………especially the bigger pins and joints. A lot of the time you can see the cracks in the solder but not always. I recently fixed a VHS / combo TV for an older gentleman in my neighborhood and it was a bad solder joint. Never knew exactly which one it was. Could not find any bad caps……..so last resort was to just reflow a bunch of solder joints. Problem fixed. (Got lucky)

5) If after spending a lot of time and no schematic or no luck in repairing, I would just call it a wash, give up and move on.

Hope this helps. Some of it has already been talked about, but thought it wouldn’t hurt to mention.

WarHawk-AVG
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hiuintahs wrote:
Back in the 90’s I repaired a lot of VGA monitors. Most of them I did not have schematics…….(simply too many different brands). The problems were similar. If no schematic available this is what I would do:

1) Check the internet with model number to see if anyone has posted any info on a similar problem. If one person has a particular problem is means others probably are too. See if anyone is talking about it.

2) Check for bad capacitors. Have to use an ESR (effective series resistance) meter. I never worry about checking capacitance. It’s the ESR that is the issue. Most of the time you can check ESR in circuit without removing the capacitor. Only in situations where the capacitor is in parallel with a low impedance item like an inductor do you get a false reading……..but that reading will make it look good. But if you get a bad reading in circuit, then the cap is definitely bad. The electrolytic solution dries out over time and generates a series resistance to the capacitance. If there is a lot of ripple current and filtering going on with that cap, then the added resistance increases the power that will be dissipated by the capacitor and that can cause the cap to get hot and bulge. The ESR problem tends to show up with the higher voltage caps and the bigger value ones. Those are the ones I check first.

3) Bad caps can also cause a power semiconductor like a mosfet, power diode, or other heat-sinked semiconductor associated with that cap’s circuitry to go bad. If after replacing a bad cap and it still doesn’t work, then need to look at the power semiconductors. Mostly look for shorts with DMM.

4) Bad solder joints occur over time………especially the bigger pins and joints. A lot of the time you can see the cracks in the solder but not always. I recently fixed a VHS / combo TV for an older gentleman in my neighborhood and it was a bad solder joint. Never knew exactly which one it was. Could not find any bad caps……..so last resort was to just reflow a bunch of solder joints. Problem fixed. (Got lucky)

5) If after spending a lot of time and no schematic or no luck in repairing, I would just call it a wash, give up and move on.

Hope this helps. Some of it has already been talked about, but thought it wouldn’t hurt to mention.


Yup

Model # plus Google/Youtube = your friend (same thing goes for linux as well Wink )

And I too did almost that exact same troubleshooting method as well…without a schematic it’s hard to troubleshoot unless there is a smoked part that is glaringly evident…

klrman
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Thanks for the help everyone.  So far I have not isolated the problem.  Also saw a video of a talented tv repair guy that fixed one board and then tv still did not work.  Long story short, he found shorts in all boards and repaired them one by one and finally got it to work.  His skills were way above mine.

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