LG W2442PA-BF wont power on.

[selldoor]

Re: LG W2442PA-BF wont power on.

Ok That resistor is the right values but not sure about the type. Anyway wait and see what Rtech comes up with and then re-think it - the post and packing or minimum order may be prohibitive.

That Mosfet looks off with zero for the 1 to 2 Next step would be to take it off the board and re-test

[Rtech]

Re: LG W2442PA-BF wont power on.

Okay with multimeter set to 200 ohms..
Mostfet STK0765
a) black on pin 1- red on pin 2 - 0.08
b) black on pin 1- red on pin 3 - out of range
c) black on pin 2- red on pin 3 - out of range

But with multimeter set to 2k ohms..
a) black on pin 1- red on pin 2 - 0.000
b) black on pin 1- red on pin 3 - 0.315
c) black on pin 2- red on pin 3 - 0.315

Not sure exactly what that means?

Looks like it it has had it, and it will need replacing.It is an N Channel Mosefet, 700V, 7amps and an Rds on of 1.2Ω.I can let you have a tested,
FQPF80N60C,N CH,600v,7.5A,1.2Ω,which will do nicely.

[Trune]

Re: LG W2442PA-BF wont power on.

Looks like it it has had it, and it will need replacing.It is an N Channel Mosefet, 700V, 7amps and an Rds on of 1.2Ω.I can let you have a tested,
FQPF80N60C,N CH,600v,7.5A,1.2Ω,which will do nicely.

That would be very kind of you.

The smps is a laf00001, not sure how to test that yet. Will research.

[Rtech]

Re: LG W2442PA-BF wont power on.

That would be very kind of you.

The smps is a laf00001, not sure how to test that yet. Will research.

It would seem that,the LAF00001,'MAYBE' an LG Part Code.And info on the internet,thought it was a FAN7601,supposedly used on an LG194WT-SF.As I have the Board for the latter I can confirm that the FAN7601 is used in that.
They are freely available in the UK on Ebay for under £4.Maybe some one has a PSU schematic for your Board which may be helpful,for confirmation,circuit layout etc of SMPS chip.

[retiredcaps]

Re: LG W2442PA-BF wont power on.

Okay with multimeter set to 200 ohms..
Mostfet STK0765
a) black on pin 1- red on pin 2 - 0.08
b) black on pin 1- red on pin 3 - out of range
c) black on pin 2- red on pin 3 - out of range

But with multimeter set to 2k ohms..
a) black on pin 1- red on pin 2 - 0.000
b) black on pin 1- red on pin 3 - 0.315
c) black on pin 2- red on pin 3 - 0.315

Not sure exactly what that means?

When testing for a short, there is really no need to test it at the 2k ohms range. All we are interested is if the reading is less than 30 ohms.

0.08 is shorted. It should be desoldered and verified out of circuit.

[Trune]

Re: LG W2442PA-BF wont power on.

Cheers, hopefully have time to test off circuit tonight.

Did anyone have any thoughts on the resistor, did you find one Rtech?

[selldoor]

Re: LG W2442PA-BF wont power on.

Still looking - size seems less reliable a guide when you get away from standard resistors
but it will be 2 or 3 watt.
When you get the mosfet out test the pads where pins 1 and 2 were to check if it still shows short.

[Rtech]

Re: LG W2442PA-BF wont power on.

Have the resistor and the replacement Mostfet as advised...have you ordered the SMPS chip ?/

[Trune]

Re: LG W2442PA-BF wont power on.

Ok MOSFET is shorted still out of circuit.
No short on board with MOSFET removed.

I haven't ordered smps chip, would you advice to do that before trying the other two or replace all three? Happy to do that just wasn't sure what best practice was

[Rtech]

Re: LG W2442PA-BF wont power on.

Sometimes the SMPS can fail also, sometimes it does not,and I have seen the latter more than the former,so replacing the Mosfet and resistor,may well be all that is required.

[Trune]

Re: LG W2442PA-BF wont power on.

Does it risk blowing all the other items again normally?

[Rtech]

Re: LG W2442PA-BF wont power on.

Not usually...

[Trune]

Re: LG W2442PA-BF wont power on.

Ok, I ordered one. But I think I will replace the other two components first if it shouldn't do damage. Just interested to see what things were gone.

[Trune]

Re: LG W2442PA-BF wont power on.

Thanks so much received components, the resistor seems a bit different does that matter? It's a 0.39 I think although multi meter reads 0.06

Thanks will try fitting them

[Trune]

Re: LG W2442PA-BF wont power on.

That's a shame,replaced resistor and MOSFET and still no luck.
So replaced SMPS and tried again, resistor blew up again.
Also saw spark from base of board, but can't see any other damage. Whether the spark came through from resistor not sure.

Not sure where to go from here.

[selldoor]

Re: LG W2442PA-BF wont power on.

You didnt have the legs too long and they shorted on the frame?

Test the mosfet again and the two fuses.

Check those 4 diodes and post the results this time.

Check for a short on the resistor pads.

[Trune]

Re: LG W2442PA-BF wont power on.

MOSFET and two fuses are fine. No short on metal case board goes in upside down.

Diodes
D105 - 544 - 0.870m ohms
D104 - 541 - 0.800m ohms
D107 - 538 - 0.784m ohms
D106 - 537 - 0.744m ohms

Resistor pads do you mean with resistor removed? I checked that before fitting new and no short. With resistor in and blown it shows momentary short with continuity test.

[selldoor]

Re: LG W2442PA-BF wont power on.

=Ok - they still look good - I meant with resistor out - couldnt remember if you had done that before - I dont understand if there is no short showing why did it blow!! - Can we see your soldering handywork.

Could you see any more damage to the board re the spark

[Rtech]

Re: LG W2442PA-BF wont power on.

Short of taking out every component around the mosfet, SMPS etc,and testing them individually there is not a lot more you can do.Will give it some more though in the morning !!!

[Trune]

Re: LG W2442PA-BF wont power on.

Yeah can get a pic.

What about the fact the resistor wasn't the same value as old one, does that not matter?

The spark could have just been the resistor I suppose, it was same area but resistor body was on underside obviously.

Although the fact exactly the same component blew after replacing the smps I guess there's a big issue elsewhere.

I'm not sure my soldering can be called handy work, I think it's okay though.