Hybrid failure already? LG42PC1D

[caspermccormack]

Hi Lads,


Back again with a short lived repair. Got the TV back, no picture but sound was still on, and it was not powering itself off, pulled of the back to see if the the fuse was blown as before on the Y-sus board which would lead me to maybe a failed Hybrid module, fuse was fine . Anyway checked across the the pins on the hybrid and it is shown a short between ground and 15v pins (2). is this telling me that the new part is shot already, think it's only in 4-6 weeks!!

Here was the original post
https://www.badcaps.net/forum/showthread.php?t=20007

[tom66]

Re: Hybrid failure already? LG42PC1D

15V and ground is a rare short; possibly something else on the Y sus instead. For these LG chassis, they use a flyback converter on the Y sus to provide 15V power - if the diode for this shorted it would appear like a dead short across 15V and ground.

[caspermccormack]

Re: Hybrid failure already? LG42PC1D

Tom can you locate the fly back on the picture for me and I can then check that for a short?


Cheers

[tom66]

Re: Hybrid failure already? LG42PC1D

It's the yellow transformer on the board (not the ones on the daughter cards for -Vy and Vscn.)

[caspermccormack]

Re: Hybrid failure already? LG42PC1D

sound, i'll take a look later on.

[caspermccormack]

Re: Hybrid failure already? LG42PC1D

Sorry for the long delay, only getting to look at this tv now, Anyway got some more info from my pal who owns the tv, it seems like there was a power surge in the house, his tv went down and also the washing machines pcb is knackered. So the fact that the tv powers up and stays on, I'm hoping that the hybrid is ok. I checked the Va's and the Vs and both are spot on as is the 5v out. So looks like the the y sus, but where to begin?????? any ideas?

[caspermccormack]

Re: Hybrid failure already? LG42PC1D

Where do i check for 15v outputs?

[tom66]

Re: Hybrid failure already? LG42PC1D

Can't remember exactly, near the yellow transformer usually.

[caspermccormack]

Re: Hybrid failure already? LG42PC1D

I'll stick up a photo, do you think it's the flyback or a resistor feeding into the flyback?

[caspermccormack]

Re: Hybrid failure already? LG42PC1D

I can see a small pad just above the 15v, i imagine that's the one. Will ineed it connected to the buffer board to test or will i get a reading from the psu to the ysus only?

[tom66]

Re: Hybrid failure already? LG42PC1D

You should be good without the buffers connected. That test pad just above the "Vy" looks okay. I suspect the output may be relative to -Vy, so if it fails to give a sensible reading try testing between 15V and -Vy.

[caspermccormack]

Re: Hybrid failure already? LG42PC1D

Hooked it up with all boards connected, -Vy to the 15v pad is shown 21v.

[tom66]

Re: Hybrid failure already? LG42PC1D

Hooked it up with all boards connected, -Vy to the 15v pad is shown 21v.

Seems a bit high may be the reason the hybrid died. Is there an adjust point for it?

[caspermccormack]

Re: Hybrid failure already? LG42PC1D

no, don't see one, i'll go over it again tomorrow, cheers Tom!

[caspermccormack]

Re: Hybrid failure already? LG42PC1D

No pot for trimming, removed the hybrid and the short seems to be on the board, on the component side it is printed 18v and on the reverse side it has 15v.

[vinceroger69]

Re: Hybrid failure already? LG42PC1D

a post in your old thread might help by adding a extra cap?

One word of caution; be sure to check that supply voltage to the IPM is stable +15V (or +18V) and of correct level. A bad supply could cause the new IPM to blow. This is because the supply is used for all gate drive circuits in the IPM and a too low gate drive voltage could cause too high power dissipation in the IPM power FET's.
Sometimes I use to add a 47uF cap directly between +15V supply and GND to improve ripple rejection close to the IPM.

[caspermccormack]

Re: Hybrid failure already? LG42PC1D

If i throw up a photo, can you show me where I need to add the cap??
Thanks for your help vinceroger!!

[vinceroger69]

Re: Hybrid failure already? LG42PC1D

i am not sure myself maybe worth asking PowerAmpFreak who posted that information will tell us?

[tom66]

Re: Hybrid failure already? LG42PC1D

Post a picture of the board on the underside - I'll highlight a potential candidate location.

[caspermccormack]

Re: Hybrid failure already? LG42PC1D

Hope these are ok?






I take it that I should not have a short between 15v and ground with the board removed?