Vizio VW42L -No Power/Fuse keeps blowing

[vote4pedro]

Re: Vizio VW42L -No Power/Fuse keeps blowing

I get 0.5 ohms (200 ohm scale) when I test were pin 1 & 4 would be on the green board itself.

when I test pin 1 & 4 on the bridge itself in ohms (2K ohm scale) I get like .993k ohms, wait a few minutes test it again and I get a higher reading on pin 1 & 4.

thanks,

[budm]

Re: Vizio VW42L -No Power/Fuse keeps blowing

The shorted circuit is on the board, more likely to be shorted out MOSFET's

[budm]

Re: Vizio VW42L -No Power/Fuse keeps blowing

Per your picture, in the middle of the board you can see one 3-pin device on the heat sink, and two more? under the heat sink that cannot be seen in the picture.
Just label the pin as 1, 2, and 3. Take the Ohm (200 Ohm range) reading of the pin combinations.
1 & 2
1 & 3
2 & 3
Report what you read, the p/n on the devices will help also.

[vote4pedro]

Re: Vizio VW42L -No Power/Fuse keeps blowing

bud

Let me make sure I understand.

Are you refering to this device I have circled in the attached pic? You say there is two more of these devices under the heat sink?

Do I do these tests with the MOSFET still attached to the board?

Thanks,

[budm]

Re: Vizio VW42L -No Power/Fuse keeps blowing

Yes, and there are one or two more on that same heatsink since I can see the mounting screws.
You can test them in place, best are top remove them.

[vote4pedro]

Re: Vizio VW42L -No Power/Fuse keeps blowing

OK, I finally got the reading and I posted some pics.

I went out and borrowed me a good fluke meter to make sure I was getting good accurate reading, the reading for Q801, Q601, Q602, & D803 was done with them attached to the board.

Q801
Pin 1-2 = 0.4 ohms
Pin 1-3 = 13.2 ohms
Pin 2-3 = 13.2 ohms

Q601
Pin 1-2 = 9.7 ohms
Pin 1-3 = 0.3 ohms
Pin 2-3 = 9.7 ohms

Q602
Pin 1-2 = 1.7 ohms
Pin 1-3 = 0.4 ohms
Pin 2-3 = 1.7 ohms

I tested D803 and got 577 ohms


I re-tested the bridge since I had it already off the board with the fluke meter and on pins 1 & 4 I got (506 K ohms)

Thanks

[tom66]

Re: Vizio VW42L -No Power/Fuse keeps blowing

All of those readings make the FETs look like they are blown.

[vote4pedro]

Re: Vizio VW42L -No Power/Fuse keeps blowing

In your experience is this common for all the FET's to go bad at one time like this?

[vote4pedro]

Re: Vizio VW42L -No Power/Fuse keeps blowing

Do you know of a good online place to order these MOSFET?


Thanks for all your help, I will post the results....

[killian6pk]

Re: Vizio VW42L -No Power/Fuse keeps blowing

Do you know of a good online place to order these MOSFET?


Thanks for all your help, I will post the results....

List the numbers off of each FET and someone will help you find the correct ones to order. You can also try www.digikey.com and imput the first row of numbers into their search field and sometimes you will get lucky and the correct component will be highlighted. If you are unlucky then the part number is obsolete and we will have to find the DataSheet for your part and then find a comparable part to order. If you try DigiKey make sure that you get the same package type as what yours are. There are many different package types for components in the same family.

[tom66]

Re: Vizio VW42L -No Power/Fuse keeps blowing

In your experience is this common for all the FET's to go bad at one time like this?

Sometimes if one blows, it can wound the others. Usually the first failure has a very low resistance, and the secondary failures have higher resistance. In your case I'd guess Q602 went first and took out Q601 and Q801.

However, please remove Q601, Q602 and Q801 and test out of circuit to confirm if they are failed.

[vote4pedro]

Re: Vizio VW42L -No Power/Fuse keeps blowing

I have removed Q801, Q601, & Q602 from the board. Here is what I got.

Q801
Pin 1-2 = 0.1 ohms
Pin 1-3 = 13.0 ohms
Pin 2-3 = 13.0 ohms

Q601
Pin 1-2 = 10.1 ohms
Pin 1-3 = 0.1 ohms
Pin 2-3 = 10.1 ohms

Q602
Pin 1-2 = 1.4 ohms
Pin 1-3 = 0.1 ohms
Pin 2-3 = 1.4 ohms


Does it appear that there still bad?


Thanks,

[tom66]

Re: Vizio VW42L -No Power/Fuse keeps blowing

Yes, all are shorted. Is there still a short across the + and - of the bridge?

What are the part #'s on those FETs?

[vote4pedro]

Re: Vizio VW42L -No Power/Fuse keeps blowing

When I read the bridge in Ohms with it out of the board, i get (502.5 K ohms) across the (+) and (-) pins. Is the bridge bad also?

Here are all the part numbers:

Bridge
D25XB 60 BA475

Q801
all I see on this is two circles with an (2) and (E) in those circles

Q601
P11NK50ZFP
GK1EA V6
CHN 724

Q602
P11NK50ZFP
GK2EN V6
CHN 723


Thanks again for helping

[vote4pedro]

Re: Vizio VW42L -No Power/Fuse keeps blowing

I was wondering if you had a chance to view the reading on the bridge to see if it was bad also.

I have listed all the part numbers also, does those numbers look correct?


Thanks

[tom66]

Re: Vizio VW42L -No Power/Fuse keeps blowing

Sorry... didn't notice this thread had an new post.

502.5k is good - no short. If TV has a separate standby section it should work without those fets.

[vote4pedro]

Re: Vizio VW42L -No Power/Fuse keeps blowing

Do you know roughly how much these 3 FET's would cost?

I'm not sure if the TV has a separate standby section. Is there a way to check? If it does would it be safe to run it with out the FET's in place?



Thanks,

[tom66]

Re: Vizio VW42L -No Power/Fuse keeps blowing

Do you know roughly how much these 3 FET's would cost?

I'd guess under $15, probably under $10. In a 42" LCD, they wouldn't use expensive FETs.

I'm not sure if the TV has a separate standby section. Is there a way to check? If it does would it be safe to run it with out the FET's in place?

Almost every TV >=32" has a separate standby section. On second thoughts the TV could try and do a self-test of the main power supply so it might give a false positive. Best to wait until the FETs are fitted...

[vote4pedro]

Re: Vizio VW42L -No Power/Fuse keeps blowing

Does those part numbers seem to look correct for the FET's?

For Q801 - all i could find on it was an (2) and (E) both had a circle around them.


Thanks,

[tom66]

Re: Vizio VW42L -No Power/Fuse keeps blowing

Hmm. That would possibly be a proprietary or custom part. Your best bet is to choose one that is way overrated for the job, like thus:

http://www.digikey.com/product-detai...63-5-ND/654637

This should handle a 42" LCD TV load easily.