vizio VW42L voltage too high help

[marlboroa]

Hello, I have a Vizio VE42L that im trying to fix. It does not have sound, picture or backlight. I can turn it on at the side panel and the light will go from amber to white. I can not turn it off. it has to be unpluged.
I have tested the output voltage at the power supply and they seem way to high.

My 5 volt reads 7 almost 8
12 volt reads 18
24 volt reads 37-38

were should i start checking? I dont see any capacitors that "look" bad but they could be. could anything on the main board or t-con board make the voltage this high? I also checked the incomming voltage at the fuses on the main board and they both read 7 volt. Any help would be a big help.

[budm]

Re: vizio VW42L voltage too high help

Did you verify the meter by measuring a batteries, just to be sure. Also check the meter's batteries.

[retiredcaps]

Re: vizio VW42L voltage too high help

It would also help if you posted the make and model or a picture of your multimeter.

[tom66]

Re: vizio VW42L voltage too high help

Very common with cheaper meters to measure too high a voltage when running on a low battery.

Notice they're all about 50% higher than they should be.

[marlboroa]

Re: vizio VW42L voltage too high help

I'll change out the battery tomorrow as I did notice that the beeper is sounding weak. It's been a good meter to me. I do a lot of pinball repairs and it has not failed me yet. I really need to buy a ESR.

[marlboroa]

Re: vizio VW42L voltage too high help

ok changed out my meters batteries and everything looks alot better.
comming out of the power supply i have
25.1 volts
12.36 volts
5.17 volts


I checked the volts at the fuses on the main board and got 12.47 at F1 and 5.15 at F2
then i checked the u chips on the main board. these readings are from top to bottom.

U2
2.12
3.28
2.03

U7
3.27
1.01
0.02

U8
5.15
3.28
2.03

U9
3.27
1.50
0.00

U33
5.12
3.27
2.02


What do i check now? It would seem that U9 and u7 are bad?

[tom66]

Re: vizio VW42L voltage too high help

What are the part #s for each of the "U" chips?
e.g. LM1117-18 indicates a 1117-type regulator, 1.8V output, made by National Semiconductor ("LM".)

[marlboroa]

Re: vizio VW42L voltage too high help

U2, U7, U8, U33 are all AMC117
U9 is a K117s15

[tom66]

Re: vizio VW42L voltage too high help

No number after AMC1117?

[marlboroa]

Re: vizio VW42L voltage too high help

AMC117 F06461 Maybe? its very hard to read and i tried to get a good pic of it.
the other one is K117s15 612

[marlboroa]

Re: vizio VW42L voltage too high help

i have .15 on either side of the fuse on the t-con board if that helps any. the inverter light is not on either. I did try this

Dont know if this matters, bu I just jumped 5V to pin 13 on J1 and the backlight came on....I will do the tests that you suggested. Thank you

when i jumped it my backlight came on too.

[Mr Bill]

Re: vizio VW42L voltage too high help

What do i check now? It would seem that U9 and u7 are bad?
U9
3.27
1.50
0.00

U7
3.27
1.01
0.02

U9 is good. It's outputting 1.5v K117s15

U7 is bad. It should be outputting 1.8v and it's only giving you 1.01v

I repaired a GV42L that had a bad regulator and the bulbs didn't turn on until that regulator was replaced. It was getting 24v all the way to the master and slave inverter.

[marlboroa]

Re: vizio VW42L voltage too high help

ok i have a spare board set from another tv. it has the following parts.

AMS117 0618
AMS117 1.8 0623
AMS117 3.3 0621

Can i use the AMS117 1.8 as a replacement for U7

[Mr Bill]

Re: vizio VW42L voltage too high help

U7 is an adjustable regulator so you would need to replace it with an adjustable regulator. The first one in your list is an adjustable 1117 regulator. If it had a -33, -18, -25 it would be a fixed regulator.

[marlboroa]

Re: vizio VW42L voltage too high help

ok so i can use the first one on the list. I have alot of them. should i change the caps around u7 while im there?

[tom66]

Re: vizio VW42L voltage too high help

No need to change the caps for now. They are under much less stress than other parts.

[marlboroa]

Re: vizio VW42L voltage too high help

i changed out U7 for the one that i had. TV works perfect now. Thanks for all the help and ill have plenty more tv's to fix. for some reasone they only last about 3-4 years.

I only asked about the caps because on some of the pinballs that i fix if you dont change out certian capacitors then you will blow a new transistor. Its wierd how they work.

Again thanks to all who helped.

[marlboroa]

Re: vizio VW42L voltage too high help

ok not completly fixed yet. I can not get either HDMI or red, yellow,white, inputs to work. It does display the Vga input great. what should i look at now or do i have a 42" computer monitor?

[marlboroa]

Re: vizio VW42L voltage too high help

ok i got vga and av 1 and 2. I can not test componet but i can test the HDMI and i dont have either of them. they just display random stuff. sometimes grey lines. sometimes colors just random stuff.

[tom66]

Re: vizio VW42L voltage too high help

Check your replacement regulator is giving 1.8V. Also, check if there are any other regulators, maybe one powers the HDMI and it is giving problems.