Insignia ns-42pdp (lg pdp42x30000)

[DaveL]

Re: Insignia ns-42pdp (lg pdp42x30000)

I removed the Y board and performed the test on the IPM as they showed..
I got no readings or audible from my meter...
I done the test with the IPM still on the board.

[tom66]

Re: Insignia ns-42pdp (lg pdp42x30000)

Ok, along the vertical heatsink on the Y-sustain can you try testing all the transistors mounted to it? From memory there are five.

[DaveL]

Re: Insignia ns-42pdp (lg pdp42x30000)

Do you test those on the "ohms" field of the meter?

[tom66]

Re: Insignia ns-42pdp (lg pdp42x30000)

You can use diode test or 2000 ohm range. Diode test is preferred. Just measure across all three pin combinations looking for shorts. (1-2, 2-3, 3-1) number the pins mentally, no need to have a specific order but be consistent from device to device.

[DaveL]

Re: Insignia ns-42pdp (lg pdp42x30000)

Ok...using the diode test on the meter..
There is a total of 5 mosfets..
The first 2 are labelled W9NK70Z
The remaining 3 are labelled FDA 59N25
On the first 2 I get no reading or audible sound..
On the remaining 3 I get readings and a audible sound from the meter..

[tom66]

Re: Insignia ns-42pdp (lg pdp42x30000)

Ok using this diagram in this datasheet
https://cdn.badcaps-static.com/pdfs/...6772f172bc.pdf

Can you indicate what pins you measure shorts (beep) -- G,D,S?

[DaveL]

Re: Insignia ns-42pdp (lg pdp42x30000)

1st FDA 59N25..mounts in the center of heat sink...
G: NO D: + S: - Audible w/reading of .005
G: + D: NO S: - Reading of .089 No audible
G: - D: NO S:+ Reading of .089 No audible
G: - D: + S: NO Reading of .089

2nd FDA 59N25
G:NO D:+ S:- Audible w/reading of .005
G:+ D:NO S:- Reading of .089 No audible
G:- D:NO S:+ Reading of .089 No audible
G:- D:+ S:NO Reading of .089 No audible

3rd FDA 59N25
G:NO D:+ S:- Audible w/reading .006
G:+ D:NO S:-Audible w/reading of .010
G:- D:NO S:+ Audible w/reading of .009
G:- D:+ S:NO Audible w/reading of .009

[tom66]

Re: Insignia ns-42pdp (lg pdp42x30000)

Ok I'm a little confused by what you mean by "G: NO D: + S:" and others... can you please explain. Is that D-S measurement, or G-S measurement, or G-D measurement?

Either way those FETs look failed to me.

[DaveL]

Re: Insignia ns-42pdp (lg pdp42x30000)

G is GATE
D is DRAIN
S is SOURCE
+ is positive lead
- is negative lead

[DaveL]

Re: Insignia ns-42pdp (lg pdp42x30000)

Here is the readings from the first 2 marked W9NK70Z

G:NO D:+ S:- NO READING
G:+ D:NO S:- .715
G:- D:NO S:+ .219
G:- D:+ S:NO NO READING

G:NO D:+ S:- NO READING
G:+ D:NO S:- .753
G:- D:NO S:+ .222
G:- D:+ S:NO NO READING

[tom66]

Re: Insignia ns-42pdp (lg pdp42x30000)

G is GATE
D is DRAIN
S is SOURCE
+ is positive lead
- is negative lead

Ok, so by
G: NO D: + S: -

you mean
Nothing on gate (G)
Positive lead on drain (D)
Negative lead on source (S)

right?

[DaveL]

Re: Insignia ns-42pdp (lg pdp42x30000)

Right

[tom66]

Re: Insignia ns-42pdp (lg pdp42x30000)

OK, looks like you've found the failed devices. Do you think you can remove them from the circuit, without damaging the board? Since it is a two layer board, you need to be careful not to overheat it. I would recommend a min 50W temperature regulated soldering iron.

[DaveL]

Re: Insignia ns-42pdp (lg pdp42x30000)

Yes sir...I have a 80w iron and a 140w gun..
Do the numbers sound right on the first 2 (W9NK70Z)?

[tom66]

Re: Insignia ns-42pdp (lg pdp42x30000)

Yes the first two look OK. Primarily I'm looking at short circuits between drain and source.

[DaveL]

Re: Insignia ns-42pdp (lg pdp42x30000)

I guess I will have to order these...the local supply house doesn't have them.

[tom66]

Re: Insignia ns-42pdp (lg pdp42x30000)

Yes, but first I think it's best to remove them from the circuit and do some more tests, just to make sure they are actually bad.

[DaveL]

Re: Insignia ns-42pdp (lg pdp42x30000)

ohhhh ok...I'm getting ahead of myself. lol!

[DaveL]

Re: Insignia ns-42pdp (lg pdp42x30000)

I got them out..
I get and audible tone across all pins in every directions..on all 3 mosfets..
Reading of 10 and less...

[tom66]

Re: Insignia ns-42pdp (lg pdp42x30000)

Yep, they are bad then.

Can you install the board with those devices removed then check if -Vy is restored to its nominal rating. No image (or only a very faint one) is expected to appear on the display.