Vizio VW42L HDTV10A no picture or sound

[questor42]

My Vizio Vw42L HDTV10A Turns on with the power button, the light changes from amber to white and the back light comes on, but there is no sound or video.

Went through all the Vizio posts for repair info.

Checked all the DC-DC converter voltages and the power supply input on the main board.

Fuses on main board, power supply and each fuse on inverter boards are good.

All measurements from circuit board ground.

Replaced u7, u8, u9 and u33
Replaced all the caps in the regulator section, I am waiting for some
parts to build a ESR meter so it was easier to just replace the caps.

Went through the flow chart in the service manual and think I found a problem at R20 it had 5 volts with no power and 0 volts with the power on.
manual calls it OPWRSB I have no idea what it stands for ?

Voltage at the regulators are

pin 1 2 3

u7 off 0 0 0
on .04 1.52 4.03

u8 off 2 3.29 5.13
on 2.05 3.29 5.08

u9 off 0 0 0
on 0 1.25 4.03

u33 off 0 0 .5
on 2.72 4.03 5.04

I need help with this, I just can't seem to track down
the problem with out having the Main Board Circuit Diagram.

Thanks for any help you can give me with this.

[Dgtech]

Re: Vizio VW42L HDTV10A no picture or sound

Well, someone's selling the Power boards really cheap on ebay. Item number 120733285981 . This is the cheapest that I have seen it on there. Of course, I am the one selling it. LOL

I bought this set in non working condition from a guy and put it into storage. Once I got a chance to work on it, I fixed the inverter board and it was fine. Then whenever I finally moved my stuff into my new house, the screen got busted. So now I'm dealing with it by selling off the boards. The power board works fine. Of course, If you simply need resistance checks from this board, I definitely will help you out as long as I have it.

[questor42]

Re: Vizio VW42L HDTV10A no picture or sound

It's too bad that the power supply is not the problem, it would then be a cheap & easy fix
mine has all the correct voltages coming out.
If I could find the correct mail board # 3642-0222-0150 4a or 3642-0132-0395
I would just buy it at this point.

[questor42]

Re: Vizio VW42L HDTV10A no picture or sound

As of yesterday I had borrowed a esr meter and replaced all the caps I did not like with higher esr values than new caps and it still is not showing a picture or sound.
Can someone help me with this please.

Thanks

[PlainBill]

Re: Vizio VW42L HDTV10A no picture or sound

1. The output voltage of U33 is wrong. It should be 3.3 volts

2. What part did you use to replace U33?

3. You need more practice soldering.

PlainBill

[questor42]

Re: Vizio VW42L HDTV10A no picture or sound

U33 was replaced with a AMC1117

My soldering skills are fine, I was out of fine solder and had to use a thicker grade and the picture was taken before the extra solder was removed with solder wick.

Also It was worked on by someone else before I took it out of a free pile at a yard sale, it had 4 different Cap brands on it.

Set is fixed now it turns out that CE27 that had just been replaced was bad.
ESR was over 4 ohms, Once it was replaced U33 was @ 3.31 volts

So less then $20.00 in parts for a free TV is a deal I'll take anytime

[CtrlAltDel]

Re: Vizio VW42L HDTV10A no picture or sound

Congrats! I rescued the same tv from the landfill for $10 worth of caps. I was lucky,they were on the power board and obviously bulging.

Good deal.

[fire72315]

Re: Vizio VW42L HDTV10A no picture or sound

Exactly what caps did you replace? I have exact same problem. Mine will power on and light up. However no sound or picture and I have to unplug power cord to turn off.

[rmoody]

Re: Vizio VW42L HDTV10A no picture or sound

Sweet Jesus, you guys saved me a bunch of money (I hope) my U33 was reading inaccurate VDC and i don't have an esr so i thought i would pull CE27 and check it with a multimeter and sure enough it's a bad cap. I just hope it's the only bad one i have. I'll get back after i get a new cap in. Problem is finding one locally. One question I have is where can I find a Manual with the Schematics of these boards? Without you guys noticing the U33 voltage being wrong i would have never known the problem. Oh and my screen would comes up with thick vertical multi colored lines. I'm just hoping this is my only problem. Check attachment. Also while the Tv is on in this condition the power button will NOT work, The only way to power it off is by unplugging it.

[PlainBill]

Re: Vizio VW42L HDTV10A no picture or sound

Sweet Jesus, you guys saved me a bunch of money (I hope) my U33 was reading inaccurate VDC and i don't have an esr so i thought i would pull CE27 and check it with a multimeter and sure enough it's a bad cap. I just hope it's the only bad one i have. I'll get back after i get a new cap in. Problem is finding one locally. One question I have is where can I find a Manual with the Schematics of these boards? Without you guys noticing the U33 voltage being wrong i would have never known the problem. Oh and my screen would comes up with thick vertical multi colored lines. I'm just hoping this is my only problem. Check attachment. Also while the Tv is on in this condition the power button will NOT work, The only way to power it off is by unplugging it.

Where are you located? In the USA it is very difficult to find appropriate caps locally. On the other hand, Digikey has a very good inventory and will ship small orders First Class Mail, which will get the order to you in two days for about $3.00 shipping.

Vizio manuals are very hard to find. My best source for manuals is Elektrotanya.

PlainBill

[questor42]

Re: Vizio VW42L HDTV10A no picture or sound

One more problem with the set that I did not know about till I exchanged my cable box for the HD version yesterday.
Everything works fine but the HDMI video output is all garbage on the screen so I need to replace more caps, All other video output modes work great.
What section of the board should I be looking at ? Just the area of the HDMI input connector or elsewhere on the board ?

[PlainBill]

Re: Vizio VW42L HDTV10A no picture or sound

One more problem with the set that I did not know about till I exchanged my cable box for the HD version yesterday.
Everything works fine but the HDMI video output is all garbage on the screen so I need to replace more caps, All other video output modes work great.
What section of the board should I be looking at ? Just the area of the HDMI input connector or elsewhere on the board ?

Definitely replace the caps in the area of the HDMI connector, but this may also due to a bad IC.

PlainBill

[rmoody]

Re: Vizio VW42L HDTV10A no picture or sound

Well the suspect bad cap turned out good. I bought a bk 810a capacitance meter to test my caps. I've pulled a few out but haven't had any luck with finding a bad one does anyone have a clue of which caps i should check? something else besides a cap? voltages on U33 were much like the original posters readings. I can't find this board anywhere online except one place that want's $200 bucks for it. Not trying to hi-jack the thread and if you think i should, i'll start a new thread.

[rmoody]

Re: Vizio VW42L HDTV10A no picture or sound

I found a manual but it's not detailed at all and absolutely no schematic of the board from what i can tell.

[rmoody]

Re: Vizio VW42L HDTV10A no picture or sound

My U4 input voltage is reading 5.1, according to the manual it should be 3.3 Any suggestions on which caps should be checked? the one cap with sharpie markings on top is one that i pulled randomly and it checked good.

Let me know if the pic isn't good enough i took it with my phone.

[PlainBill]

Re: Vizio VW42L HDTV10A no picture or sound

My U4 input voltage is reading 5.1, according to the manual it should be 3.3 Any suggestions on which caps should be checked? the one cap with sharpie markings on top is one that i pulled randomly and it checked good.

Let me know if the pic isn't good enough i took it with my phone.

Probably not a cap. Check for continuity (less than 1 ohm resistance) from the IN pin of U4 to F1 and F2.

PlainBill

[rmoody]

Re: Vizio VW42L HDTV10A no picture or sound

NO continuity to either. Is that good or bad?

[PlainBill]

Re: Vizio VW42L HDTV10A no picture or sound

NO continuity to either. Is that good or bad?

Neither. You were expecting 3.3 V input on U4, but actually got 5.1. 5.1 Volts is a common output voltage of a power supply, I thought it might be coming directly from the main supply. This wouldn't be the first time a schematic or troubleshooting instructions had an error.

The next step would be to identify where U4 gets it's power and establish why it's too high.

PlainBill

[rmoody]

Re: Vizio VW42L HDTV10A no picture or sound

Neither. You were expecting 3.3 V input on U4, but actually got 5.1. 5.1 Volts is a common output voltage of a power supply, I thought it might be coming directly from the main supply. This wouldn't be the first time a schematic or troubleshooting instructions had an error.

The next step would be to identify where U4 gets it's power and establish why it's too high.

PlainBill

I'm a little confused, is 5.1 ok? Do you think the service manual is wrong? Should U4 actually be 5.1?

[PlainBill]

Re: Vizio VW42L HDTV10A no picture or sound

I'm a little confused, is 5.1 ok? Do you think the service manual is wrong? Should U4 actually be 5.1?

The service manual MIGHT be wrong, you might be making a mistake (yes, it happens), or there might be a bad component.

The usual design has a series of regulators. The main power supply puts out 5 V nominal (it often is .1 or .2 volts higher). The first LDO regulator drops it to 3.3 volts for the processors. The 3.3 Volts also is the supply for the 2.5 volt regulator, which in turn supplies the 1.8 volt regulator. When I see a regulator whose input voltage is too high I look for the regulator that is supplying too high a voltage.

PlainBill