50PK350 Repair Log

[ReeceyBurger123]

Brought this 50" slimline Lg Plasma for £80 off a local sales site on facebook. Has stand, remote and is full Hd so not too bad. Fault is it switches on panel lights up then the Tv shutsdown, protection circuit engages and shutsdown the Tv. Im suspecting a sustain board fault probably the Yfr fets short very common on these which loads down the Psu and causes it to shutdown.

The Vset up ramp is working as the screen primes but doesn't dim (set down ramp not engaging properly) so guessing something is shorted I bet its the 30f124 or 30j124 fets on the heatsink on the Ysus that have shorted, seen it before on the 42" version of this Tv. We shall see

TBC

[Hamie]

Re: 50PK350 Repair Log

From your description it sounds more like the common fault of the wirewound resistors failing on the power supply.

[ReeceyBurger123]

Re: 50PK350 Repair Log

Possibly Hamie, so many issues on these sets I have serviced a few not seen them resistors at fault yet seems common though from what others say. Will have to see tomorrow buddy.

[ReeceyBurger123]

Re: 50PK350 Repair Log

Well you are right Hamie one of the 2 resistors is completely open also smells burn, fets test good on the sustain boars. Got the resistors on order should hopefully sort it. I have also re-soldered the coils on the Zsus as they are prone to breaking through the solder joints on these causing issues.

[Hamie]

Re: 50PK350 Repair Log

Do you have an esr meter reecy?

[ReeceyBurger123]

Re: 50PK350 Repair Log

I dont have one at my place atm, however my uncle has on I can access. How come ?

[Hamie]

Re: 50PK350 Repair Log

There's a cap that usually fails but looks good. It will even test good with a capacitance meter.

However test it with an esr meter and it's off the chart.

It's the 16v 100uf cap usually located just below the resistors.

the FET thats also close to the reistors (the one not attached to any heatsink) will also need changed, even if it tests good.

If you change out only the resistors; the tv will work, but after a few weeks/months the resistors will fails again.

If you change the capacitor and the resistors, almost every time as soon as you apply power it will short the FET and Short the resistors (obviously the will test short anyway but they will test 1-4 ohm rather than the 10 or 22 that they are supposed to)

But if you change out the 2 resistors, the FET and the cap all is good.

There's a few stories saying to use 7-10w resistors but they will also fail in a short time if you don't change the cap and the FET.

[ReeceyBurger123]

Re: 50PK350 Repair Log

Ok cheers, will have a look at it in a min will get some parts together.

[ReeceyBurger123]

Re: 50PK350 Repair Log

Hamie, what is the Fet the one just before the resistor ? At college atm but sure its something like a str250 will let you know after.

[Hamie]

Re: 50PK350 Repair Log

sorry i cant remember the part number, think i used a sub.

addding attachment incase someone else has similar issue.

[ReeceyBurger123]

Re: 50PK350 Repair Log

Right, I replaced the resistors, the transistor also heatsunk the new one and replaced the 100uf 16v cap and the set now works Screen fired up no brun in what so ever. Now have a 50" 1080P PDP to sell whooooo ! Thanks Hamie

[comptek]

Re: 50PK350 Repair Log

picked up one of these today clicking no screen prime, turns off again, no bad caps, replaced voltage regulator just in case no dry joints the 3 wire wound resistors are all between 10.2 & 10.4 ohm 5v,17v are there, ac-detect gets up to 4.6v or so and drops off again, NO VA or VS well VS gets to 1.3v and shuts off, all fets seem ok no shorts no burn items.....
tried disconnecting ysus and zsus still doing it any ideas chaps ?

regards Gary

[sordids999]

Re: 50PK350 Repair Log

check R103,R104,R105,R106,R107,R108,R109,R110,R111,R112, R113 on the underside of the power supply board

check 3BR1565JF for shorts
and the diode next to it out of circuit just lift one leg

good luck

[ReeceyBurger123]

Re: 50PK350 Repair Log

picked up one of these today clicking no screen prime, turns off again, no bad caps, replaced voltage regulator just in case no dry joints the 3 wire wound resistors are all between 10.2 & 10.4 ohm 5v,17v are there, ac-detect gets up to 4.6v or so and drops off again, NO VA or VS well VS gets to 1.3v and shuts off, all fets seem ok no shorts no burn items.....
tried disconnecting ysus and zsus still doing it any ideas chaps ?

regards Gary

Also checked the Vson signal bud ?

[comptek]

Re: 50PK350 Repair Log

check R103,R104,R105,R106,R107,R108,R109,R110,R111,R112, R113 on the underside of the power supply board

check 3BR1565JF for shorts
and the diode next to it out of circuit just lift one leg

good luck

All resistors measure ok not open or short either, i had replaced the 3BR1565JF just in case but no shorts, diode was checked out of circuit not shorted either way.... still stumped

[comptek]

Re: 50PK350 Repair Log

Also checked the Vson signal bud ?

VS-on ? i have M-on and RL-on bud

[ReeceyBurger123]

Re: 50PK350 Repair Log

Its RLON, the relays are in place to control the power signal to turn the Vs rails on.

[comptek]

Re: 50PK350 Repair Log

Its RLON, the relays are in place to control the power signal to turn the Vs rails on.

yes bud both RL-on and M-on go to about 4v and stay up until it clicks again
strange thing though without Z sus vs goes to like 1.355v then clicks then it goes up to 1.505 for example then shuts off its like its trying to ramp up then fails

[Moreno83]

Re: 50PK350 Repair Log

Reecy , Is this symptom you had on this set the same for the 60PV250? Can i use any 22ohm resistor?

[ReeceyBurger123]

Re: 50PK350 Repair Log

Reecy , Is this symptom you had on this set the same for the 60PV250? Can i use any 22ohm resistor?

Maybe mate, have you checked the resistors for the Vs output ?