LG 42PT350 DEAD Ysus shorted Mosfets

[Ltank]

Ysus had a bunch of shorted Mosfets. Could not remove heatsinks to remove mosfets. I ordered a new EBR68341901
YSUS. My question is how do I check the buffer board?
EAX62081101. I did not find it. I don't want to damage new board if buffer is bad.

[Hamie]

Re: LG 42PT350 DEAD Ysus shorted Mosfets

There's videos for how to check each IC for shorts.
But quick way to see if board is faulty is:

From your pictures you see the 3 white connections to the y-sus.
Look at the top one. It should have 2 or 3 pins tied together. Put your DMM on diode mode and touch any of these pins. Then with the other probe touch any of the other pins not tied to the 3. If it beeps you have a shorted buffer IC somewhere.

[tom66]

Re: LG 42PT350 DEAD Ysus shorted Mosfets

See video:
https://www.youtube.com/watch?v=51SZsfH60EY

[Ltank]

Re: LG 42PT350 DEAD Ysus shorted Mosfets

Ok thanks. I will check it Friday when back st the shop. I will post my findings. Thanks

[Ltank]

Re: LG 42PT350 DEAD Ysus shorted Mosfets

Looks like the Buffer is bad. P101 are all shorted together. P102
Are all shorted together except for the 1st two by the triangle.
P106 . EBR68288401 EAX62081101

[Ltank]

Re: LG 42PT350 DEAD Ysus shorted Mosfets

Ordered a Buffer board for good price but it killed any profit because of Price quoted. I did not allow for this other cost. Should have known better. Now I won't forget next time.

[retiredcaps]

Re: LG 42PT350 DEAD Ysus shorted Mosfets

Looks like the Buffer is bad. P101 are all shorted together.

Your Fluke 87 looks like it is suffering from the classic faded digits. For a potential quick fix, see

http://mrmodemhead.com/blog/fluke-8x-faded-lcd/

[Ltank]

Re: LG 42PT350 DEAD Ysus shorted Mosfets

I finally got the replacement YSUS and Buffer board. The P.S.
does not shut down, has 200 vdc voltage. There is no picture or menu. On the Ysus output P213 labeled H.V. is 0vdc. Did I get two bad boards? With the Buffer board removed P213 has
Negative 10 vdc ? P212 labeled +15VF also has negative 10 vdc . My meter is on a good chasing gnd. Did the buffer kill the Ysus? Or did I get a bad Ysus? Confused now!

[Ltank]

Re: LG 42PT350 DEAD Ysus shorted Mosfets

Pics close up of output to buffer

[tom66]

Re: LG 42PT350 DEAD Ysus shorted Mosfets

15VF is relative to FGND i.e. The Y-sus output

[Ltank]

Re: LG 42PT350 DEAD Ysus shorted Mosfets

I checked P213 and P212 on acv and they both had 121vac?
Any idea what I am supposed to have?

[tom66]

Re: LG 42PT350 DEAD Ysus shorted Mosfets

It varies with the displayed image - you need a scope to be sure.

[Ltank]

Re: LG 42PT350 DEAD Ysus shorted Mosfets

Turns out I got a bad Ysus. Replaced it with another and get a crummy red picture caused by a bad Zsus board. Pic was taken at a angle because of crowded work area. Customer does not want the added expense on repair. Called it quits.