Another vw42l problem

[abarker8323]

Hi guys i have a vizio vw42l. I initially had a bad voltage regular on the main board. I had messed the tracing up on while removing the regulator. After attempts of trying to fix my mess up i made it worse and removed more tracing. I put the project on hold for a couple months and finally just bought a new main board. After installing new board the tv came on and everything worked great! I buttoned everything up the next day and went to turn it on, now i have nothing! Tore back apart and now i am no longer getting 24v or 12v from the power supply. The led turns orange to white and will will turn back off also. I have 5vdc coming from the supply to the main and i am getting 3.3vdc back to the ps_on. The 12v side of the main has no readings what so ever either. Please help, i am getting very frustrated. Thanks.

[martyparish]

Re: Another vw42l problem

It could be bad caps on the power board. Have you inspected them closely? Especially the ones under the heat sink.

Try warming the caps up with a hair dryer and then try to power it on.

[abarker8323]

Re: Another vw42l problem

None of them physically look bad. No bulging ends or anything. I had checked them all the prior time before i realized it was a voltage regulator. They all charged to their respective values. Where does the 24 volt and 12 volt side originate from? Is their anything that triggers them from the main board other than the ps_on?

[abarker8323]

Re: Another vw42l problem

And heat gun or freeze spray does nothing

[budm]

Re: Another vw42l problem

Lets find out first to see if the PFC voltage booster circuit is working or not. Check the DC voltage on the two legs of the large cap (450v) in the primary side of the power supply, it should have 160~170vdc when the TV is not turn on, then it should go up to about 380~390v when the TV is turn on. PS_ON turn on the PFC and the 12/24V section.

[abarker8323]

Re: Another vw42l problem

it indeed has 161 when off and 400.1 when turned on

[abarker8323]

Re: Another vw42l problem

What does PFC stand for?

[budm]

Re: Another vw42l problem

Power Factor Correction.
So the next section we need to work on will be the 12v/24v switching power supply section, it will need in-depth troubleshooting down to component level. What kind of tools do you have? Have you done any surface mounted component repair?

[abarker8323]

Re: Another vw42l problem

I have done a little. I have fixed 6 TVs so far from the forums. Caps, voltage regulators, power transistor. I have usually been able to find a post simular to the issue at had and diag from there. Not this time. I have a klien digital mm. Can read capacitance. Assortment of solder irons, solder sucker, solder wick, and plenty of room!

[budm]

Re: Another vw42l problem

OK, then for me to help you troubleshoot this power supply board, I will need really good clear pictures of the board. Please take the whole picture of the top side and the bottom side of the board, then take close up 1/4 section of board (top and bottom) so I can easily see the traces and the component designators.
I will then try to trace out the circuits and then provide you the test points and components you will need to check.
Just remember that I do not have the board in front of me to look at, so GOOD CLEAR FOCUS pictures are really important.

[abarker8323]

Re: Another vw42l problem

Sounds good, give me a few and i will get the wife digital camera and get them posted.

[abarker8323]

Re: Another vw42l problem

Hope these work. I have taken pictures for a hour and half. Harder than it looks. Let me know if you need a better one of something. I included a couple extra so you could see under heat sinks.

[abarker8323]

Re: Another vw42l problem

.

[budm]

Re: Another vw42l problem

I do not see the picture of the whole view of the bottom side of the board, the other bottom side pictures are out of focus. May be you need good day light for the light source for better pictures.
What I have to do is to print out all the pictures and then tape them together to make one big board and trace out the connections. So you understand what I need for me to be able to see.

[budm]

Re: Another vw42l problem

Ok, I see the whole bottom side, but it is not in focus.

[abarker8323]

Re: Another vw42l problem

ok. i guess that i could try that idea in the am. Dark here in wy. I will get them to you first thing in the am. Thanks alot bud for helping me!

[abarker8323]

Re: Another vw42l problem

Here is the quarters

[abarker8323]

Re: Another vw42l problem

There are some parts that are still not clear so here are 1/9ths

[budm]

Re: Another vw42l problem

OK, I just download more pictures that you posted, please give me more times to look through them.
By the way, thanks for much better pictures! Same camera that you used last night?

[abarker8323]

Re: Another vw42l problem

No, last night was 10mp on smart phone with shaky hands. Today was with 16.2mp digital camera on tripod.