VIZIO VO42L No picture, No Sound

[retiredcaps]

Re: VIZIO VO42L No picture, No Sound

I'm wondering if you have to replace all 4 even if the 2 originals measured good resistance wise? A resistance test won't catch all the faults of the mosfet.

In the latest version 0.3, I did add a case study where one bad mosfet caused 2 seconds to black.

https://www.badcaps.net/forum/showthread.php?t=17659

I'm not saying it is the problem here, but something to check as well especially if the mosfets somehow work in "pairs".

I know other people test mosfets using this procedure (simple test)

http://www.4qdtec.com/mostest.html

but I never had luck with it.

[Learningman]

Re: VIZIO VO42L No picture, No Sound

Hi. Noobie here. But I have been reading the forums and they have Been a TON of help. I've never even picked up a multimeter until about a week ago but I'm trying to learn as much as possible. I really appreciate all the knowledge on this forum and the help.
Let me first explain what I have. I also have a 42 inch vizio LCD but My model number is vw42flhdtv10a. I'm having the same problem as described by the first post in this thread. I have a black screen. I get a standby and power light. I get sound and if I hold a bright flaslight against the screen I can see the "no signal" screen saver bouncing around the screen. I can also hear sound, turn channels, change inputs, ect. I took off the back of the tv and figured that I needed the MOSFET and ic chips that everyone else is having problems with on the slave board. My inverter boards have different board numbers also. My master is 6632L-0470A and slave 6632L-0471A. I decided to check the ohms on both boards MOSFET chips. All 8 chips get about 8.2 to 8.5 ohms so I figured that wasnt my problem. I then started testing the ohms on the transformers. The two transformers on the master board both get a secondary reading of about 63 ohms and a primary of about .04 ohms. I figured that was probably normal. I then read the readings on the slave transformers but the secondary reads 1 on both transformers, that means it's not showing any resistance. It doesn't change from when the probes are in the air to touching the points. The second transformer reads exactly the same. It's kinda odd to me that they would both read that way. I figured that one transformer might have gone bad but for both to go bad just seems not probable. Do you think that it could be something else on the board causeing something to stay open or something? I have a feeling that the slave board has gone bad but I would like to fix it if possible, plus I can't even find a new slave board to buy anywhere. It looks like everybody's out of stock. Any help would be very much appreciated. Thanks.
Lman

[retiredcaps]

Re: VIZIO VO42L No picture, No Sound

1) Post top down view pictures of all your boards (back and front) following the instructions my sig file in post #61 (just above yours) exactly.

2) Also post a picture of your multimeter.

3) BTW, there is a huge difference between 8.2 ohms and 8.2k ohms. One is 8.2 and the other is 8200. When you leave out the multiplier, it leads us to incorrect conclusions. When I first read it, I thought all your mosfets were shorted with a reading of 8.2 ohms.

4) Hit the "enter" key once in a while. It makes it easier to read. The information you provided is excellent, but it is in a hard to digest format without giving the reader (us) a break once in a while. It is even more difficult to read/follow on the 22 inch and larger widescreens because it seems to go on forever and easy to lose track of the next sentence.

[Learningman]

Re: VIZIO VO42L No picture, No Sound

Thanks for the quick reply. Im sorry about the confusion I'm still trying to figure out how to read this multimeter.

I have it on 20k and all 8 MOSFET's are reading from 7.31k to about 7.35k. Is that right?

I also don't have Internet on my computer right now. I'm using my phone. I took pictures with my phone but I can't upload them to the wesite using my phone.

I read another post where people were getting a reading of 8.5k. Are my MOSFET's too low or is 7.33k in the acceptable range?
Thanks for your help

I will upload pictures when I get to a computer

[tom66]

Re: VIZIO VO42L No picture, No Sound

7.33k is not shorted so probably okay.

[Learningman]

Re: VIZIO VO42L No picture, No Sound

Here is a few pictures of my boards off the Internet. It's not my actual boards, but these are the same boards that are in my tv. What would you recommend that I try next?

I seem to have no problems with my MOSFET's but I don't know what to try next. My backlights aren't lighting so it would have to be the inverter boards right?

How would I check the caps on the inverter boards? Are they checked with ohms also? I've looked very careful at all the boards and I can't see any burn marks or bulging caps.

[retiredcaps]

Re: VIZIO VO42L No picture, No Sound

Here is a few pictures of my boards off the Internet. It's not my actual boards,

We prefer to see pictures of your boards for a number of reasons.

1) Manufacturers make revisions or even complete board changes while keeping the same lcd model number.

2) Your board, while perhaps the same, may have "aged" differently due to heat, cold, etc. Your board might have hot spots, poor soldering, glue turning conductive, etc. We have some members with eagle eyes.

3) Just a few months ago, someone posted "I changed all the bloated caps", etc, but it doesn't work. It wasn't until he posted a picture of his recapped board that I spotted another bad capacitor. The poster also claimed he had 20/20 vision (which I do not have).

[ski_messiah]

Re: VIZIO VO42L No picture, No Sound

Freezer

Do you have any update for how well the inverter modification worked?
I am ordering parts for this right now and I was wondering if you had good results.

Thanks!

[gentlek]

Re: VIZIO VO42L No picture, No Sound

not sure the bad capacitor is cause or result but it definitely involve inverter failure.

[budm]

Re: VIZIO VO42L No picture, No Sound

When those C filter caps failed, the circuits will get trmendous AC ripple feeding the circuits. You need to inspec the large PWM IC, and all the MOSFET.
http://s807.photobucket.com/albums/y...VO42LFHDTV10A/
The board should alo be updated.

[tom66]

Re: VIZIO VO42L No picture, No Sound

They are Samwha caps. Second worse caps known to man, just behind CapXon. The flux around the FET would make me suggest it has seen better days and may be dead, due to the increased current draw from bad supply decoupling.

[gentlek]

Re: VIZIO VO42L No picture, No Sound

one FET sure fried. I plan replace all 4. BD9897 need long time to arrive. thanks everybody here.

[gentlek]

Re: VIZIO VO42L No picture, No Sound

my tv is working now. I got most parts from digikey except BD9897.
MOSFET: NP90N04VDG-E1-AY
cap: EEU-FR1V681
TVS: SMBJ33CA

[pposey]

Re: VIZIO VO42L No picture, No Sound

Sorry for this stupid question but im having the same problem. My vizio Vw42L model, it has a orange light and powers on with the white light but there is no picture but does have a backlight. My question is i have a multimeter but i do not know if i have the right setting to check for these voltages, could someone please tell me what the symbol on the multimeter would be? Thanks in advance.

I also changed out the main board already thinking that was the problem but its still doing the same thing.

[tom66]

Re: VIZIO VO42L No picture, No Sound

V with solid line and dashed line, or "Vdc".

If there are multiple ranges (200m, 2000m, etc.) select "20V" or "40V".

[pposey]

Re: VIZIO VO42L No picture, No Sound

Thanks for the quick reply. I only have one that is similiar, it says "10 MegOhm input DCV" and the V has the solid line and dashed line above it. Is that it or am i out of luck?

[tom66]

Re: VIZIO VO42L No picture, No Sound

Can you post a picture of it? I or someone else can highlight the setting you need.

[pposey]

Re: VIZIO VO42L No picture, No Sound

http://*************/a/img222/3249/i...1020121612.jpg

[tom66]

Re: VIZIO VO42L No picture, No Sound

That's a decent multimeter.

Set your meter to the "DCV" ("10MegOhm input") setting.

Then plug the red probe in the rightmost socket, and the black probe in the centre socket.

There is no need to select the range, as the meter does it automatically (it is autoranging.)

Then test as previously indicated, for the majority of tests you can leave the black probe connected to the chassis (spare screw hole is a good place to try.)

[pposey]

Re: VIZIO VO42L No picture, No Sound

thank you for your help! i think i found my problem. I have the replacement board in still and its showing a weird reading on a regulator. It says on the board its U33. The input is 5.12, the tab is 2.05, the output is 1.26. is that a bad regulator?