Need Help For Troubleshoot LG 50PS11 Y-Sustain

[Jeff Pepin]

Hi !

I'm Working on a plasma Panel that Was not Priming pannel my first check
i have Disassembled All HEatsinks and Tested All Fets on it

i have found 2 of them labeled 45F122 that was Open so ive replaced em

after the rebuild ive put it back and the tv was Working BUT ..

when come time to adjust settings ( VSC , VY ) i have found that the Vsc Voltage was too low , ( 128V insead of 150V)

so ive tryed to put it back at 150 by turning the VSC VR pot and when voltage reached 143V the sustain Stopped working

i have redrop the pot to initial position , Rebooted the TV and the sustain come back again

curently if i leave VSC to 130V it work 1 - 2 Hours then the Y-sustain goes OFF , each time i try to adjust it at the label level ( 150V ) it goes OFF , the best i have been able to reach is 143V and the TV worked about 5 min before screen goes OFF

so i decided to replace ALL Electrolytic Caps on the board ( Swapped em with all of a donnor Board ) : NO CHANGE

at this time im lost and i have no more idea what can cause VSC to clip

i need to know Wich Fets actually Drive de VSC voltage for Changing them again in case i have forget one that fail on load to rule this out

Y- Sustain Board are an EAX60982502 and i join pictures of it with and without heatsink

if anyone can point me out it would be appreciated ,
Thanks !

[Jeff Pepin]

Re: Need Help For Troubleshoot LG 50PS11 Y-Sustain

Update , after all fets replaced , nothing changed , but my friend tell me that before give me the tv , he have changed somes boards , including buffers and control board comming from another tv a 50ps70 , and tell me too that is possible the control board /ysus was set to run at lower voltage (not know the donnor panel voltage ) ,, i dunno if its possible maybe .. all is possible these days ..

Strange thing too , the set running like a charm since 4 consecutive hours at 100v only on vsc , 50vless than the panel is labeled . The image is just like my other 50ps11 set at labeled vsc (150v) and i cant see difference , i understand nothing about that .. but its working .

Electronics repair can be so freak and strange ..

[Jeff Pepin]

Re: Need Help For Troubleshoot LG 50PS11 Y-Sustain

Sorry the board is not an EAX60982502 but EAX60982501

[Jeff Pepin]

Re: Need Help For Troubleshoot LG 50PS11 Y-Sustain

Hard to belive , no?

[Jeff Pepin]

Re: Need Help For Troubleshoot LG 50PS11 Y-Sustain

Update : vsc at 100v , 12 hours and screen goes off
Vsc at 120v , 3 hours and screen goes off
Vsc at 130v , 20 min and screen goes off
Vsc at 140v , 5 min and screen goes off
Vsc at 143v+ screen only flick one time and stay off

_-------------___

Anyone have idea of what could be wrong plz before i left em here and buy a working ysus

[JeffJ]

Re: Need Help For Troubleshoot LG 50PS11 Y-Sustain

Why would you neglect to adjust VSC properly once told it was out of line ( since you must not have tested it) you have probably damaged the panel or the y-sus at this point.

[Jeff Pepin]

Re: Need Help For Troubleshoot LG 50PS11 Y-Sustain

Did you ever read first post? Should be 150v , when y-sus reach 140v (vsc) the y sustain stop working , cant damage anything since it work only at inferior voltage than need to be , if it was runnig 50v over i agree it will be bad , but its not actually the case ,, and the y sus are already damaged , it is what im actually try to fix ..

[Jeff Pepin]

Re: Need Help For Troubleshoot LG 50PS11 Y-Sustain

I will change the driver transistors (Q801,802 and Q803,804 ) these 4 drive the gate of 45f122 , and these 4 snd transisors are drived by the 16 Pins irs******. Probably one of this transistor was damaged when 2 of 6 45f122 was shorted ,,

If i resume the work i have made on this sustain
First time ive checked this tv the fuse on y sustain was blown , and 2 of 6 45f122 was totally shorted ,
I have replaced the shorted 2 , and the fuse
Replugged sustain and it was buzzing like a working one but pannel was not priming

After a second check i have found 2 other 45f122 but blowed open .. so ive changed it but i have never tested the driving stage before the igbt , it is possible that one of these driver is not working and not driving new igbt's .. and probably is the reason whi i can't reach proper voltage when i try to set VSC

[Jeff Pepin]

Re: Need Help For Troubleshoot LG 50PS11 Y-Sustain

If only 3 of 6 igbt are working it will output only half of VSC wen y sustain is set tu full output ,, and it look like this a lot ,, i dont know why you say that i have not tested VSC maybe your kidding me , maybe you have difficultys to read my bad english .. so its okay