LG50PT353k

[finntricky]

Hi Guys,
got this LG plasma, with flashing stand by, took the back off, and it was so thick with sticky fluff, so took out the power supply to clean it up before checking voltages, put it back in and the tv came on, but with very spotty pic, then took out Y-SUS, again, gave it a good clean up and put it back in, turned the tv on, and BINGO, turned on great picture.
so im thinking to my self, nice easy repair job this is, took out the rest of the boards, give them all a good cleaning and then reinstall,
turn the set on and, you guessed it, no pic, no screen flash, but the tv turns on and has sound though a scart.
checked all volts and every one seems to be correct,
cant find any shorts on buffers, but has i have no flash of the screen, im thinking X-SUS,
oh, by the way, the led on the control board gives 4 flashes, the 3rd flash lasts longer than the first 2, and the 4th is quick, if that give any idea.

[dick_barton]

Re: LG50PT353k

I would be tempted to reseat all the boards once again in the hope that one of the connectors are not quite in place.

[tw2005]

Re: LG50PT353k

So where has the centre ribbon to the ZSUS disappeared to? Under the sub board?

[tw2005]

Re: LG50PT353k

Actually, just doing some extra research. It only has 2 ZSUS ribbons? found the sub board which is different to yours but suggests a running change in production.

, certainly not something I've seen before.

[finntricky]

Re: LG50PT353k

what sort of voltage should i be getting at the point x-sus to ribbon board ?, i only get 4 volts, that can't be right,
testing fets and some of the reading are strange, but take them out and test ok,

[tw2005]

Re: LG50PT353k

what sort of voltage should i be getting at the point x-sus to ribbon board ?, i only get 4 volts, that can't be right,
testing fets and some of the reading are strange, but take them out and test ok,

Not sure on this one but may be worth pulling the boards or at least the ZSUS and closely inspect th esolders particularly on those big coils. previous models have cracked through causing erratic behaviour and then the usual snap crackle and pop for a few IGBTs.
Kinda been working on some LGs lateley(forgive me) Panasonics all dried up because some fool has spread so much info on how to.

[tw2005]

Re: LG50PT353k

what sort of voltage should i be getting at the point x-sus to ribbon board ?, i only get 4 volts, that can't be right,
testing fets and some of the reading are strange, but take them out and test ok,

Is the TV running or in protect? Are the YSUS volatages normal?

[finntricky]

Re: LG50PT353k

Is the TV running or in protect? Are the YSUS volatages normal?

all voltages at test points are spot on, give or take a volt or 2.
and the tv boots fine, with sound and no picture

[tw2005]

Re: LG50PT353k

all voltages at test points are spot on, give or take a volt or 2

Well it was working, now not, If the volatages are correct on the ZSUS test points too I'd check th eboard then maybe try thr old ctrl bd jumper screen test with the main isolated. can't be much though if you had it and now lost it.

[Hamie]

Re: LG50PT353k

I had one if these a while ago with no picture.
Turned out to be a cracked joint on the transformer located on the ysus.

Might be worth having a look

[tw2005]

Re: LG50PT353k

should also mention that if the ctrl bd craps itself, you'll see nothing but will have sound. that's the issue with the one I've got, don't remember if the panel primes up or not, if I try really hard I can get some

[finntricky]

Re: LG50PT353k

checked all the solder joints, and tried the auto gen, still nothing, think ill gumtree it, let someone else have a go, not worth spending money on a 720 plasma

[tw2005]

Re: LG50PT353k

checked all the solder joints, and tried the auto gen, still nothing, think ill gumtree it, let someone else have a go, not worth spending money on a 720 plasma

Yeah, that's how I feel but if a ctrl bd surfaces real cheap, I'm in business.

[nomoresonys]

Re: LG50PT353k

Have the exact same led blinking on control board on a 50PT350: "the led on the control board gives 4 flashes, the 3rd flash lasts longer than the first 2, and the 4th is quick": also had a IC110 burnout on YDRV upper buffer, replaced the buffer, now have the control board blinking, no picture. Anyone ever figure out the problem, bad control board??

[nomoresonys]

Re: LG50PT353k

jumped the auto gen, no patterns just black, during auto gen jump the red led on front, when I power on goes red then fades out then 2 seconds later comes back on and stays on, relay clicks about 4 times sometimes more.

[nomoresonys]

Re: LG50PT353k

found 4 bad transistors on x board heatsink and D10 shorted, replaced them, still no picture no glow, there is a steady red standby led on front that goes off when I hit power, relay clicks once, have voltages but no picture or glow, just black blank screen.

[nomoresonys]

Re: LG50PT353k

rechecking z board, I called it x above, checked the transistors I replaced, getting short to ground on Q107 collector, Q110 collector and two pins of D114 also short to ground, not sure if that is normal, anyone have an idea of what might be the cause or what to check, thanks, picture from sj:
https://www.shopjimmy.com/lg-ebr7173...01-zsus-board/

[tvtimmy]

Re: LG50PT353k

Bad transistors (igbt's) on the z main will take out transistors on the y main, and vice versa. The boards are chained together. Replace all bad transistors.