omendata
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Jul 26, 2015, 7:36 PM
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50LGPK590 Common Problem Sound But No Video
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This is a nightmare common fault with plasmas and difficult to pin down.
The tv just didnt come on one morning and had the usual psu relay click and standby light.
I have repaired the psu which i thought was the issue - common problem with the two 22ohm 5 watt resistors and sometimes a diode and smps transistor on the LG PK range of televisions but the tv powers up now so I was nearly jumping for joy...until...
Just very depressing that i also have no picture but have sound now so it seems another board on the telly caused the psu resistor to blow - incidentally its usually the top resistor but i replaced both just to be safe.
I have tested the y-buffers today and they are fine - i bought a y sustain board off ebay and fitted it after testing the y-buffer boards were ok - it didnt fix the issue.
Someone has said that if you pull the connection from the z-sus to the psu and you still have sound then its the z-sus board that has the fault but i dont agree with this - perhaps someone on here can confirm this as i pulled the z-sus and there is still sound indicating that z-sus board is faulty.
Having researched for two days it seems the problem may be with the actual t-con board itself.
I think i will bite the bullet and buy a t-con board tonight and see what happens as I am sure its not the z-sus even though the advice is that it is if you still get sound when its disconnected.
Maybe someone more knowledgeable than i on here can give us some sort of clue.
I really need to get an oscilloscope to fix these things properly.
I have always got on fine with my fluke meter but for more in depth stuff like this you need and oscilloscope especially for testing the y-sus outputs.
Someone mentioned the service port on the back of the tv that repair shops use to repair tv so i connected up an rs232 cable and can now control my television via my pc using the service port but having tried to run a self diagnostic i have found that the so called "SERVICE PORT" is not a service port at all and repair shops cannot use it to diagnose a fault its merely there to allow programming of the firmware and controlling the television unless someone know what the diagnostic command is to run a self test but i doubt it would pinpoint the issue. This also makes me pretty certain that the main board is ok and its either the z-sus or more likely the t-con board.
(This post was edited by omendata on Jul 26, 2015, 7:51 PM)
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