Vizio GV42L help.

[Fastcast]

Our Vizio went haywire the other day. Acted like a bad graphics card in a computer. The picture went squiggly/static and made a bunch of crazy noise so shut it off (only way it would shut off was pulling the plug) and now all we get when turning it on is the yellow Vizio light will go to white but no back light/picture, no sound and the only way to turn it off is pull the plug again.

Got the back off and started with testing the F1 & F2 fuses and right off it seems I'm getting double voltage. F2 is coming in at 10.5 and F1 at 25....I checked a few of the regulators (U7, U9, U-etc) and same thing there, everything seems twice as much as what I've heard they should be, from my limited info from reading and watching videos.

Any ideas what might be going on?....Thanks!

[tom66]

Re: Vizio GV42L help.

Is there a little battery icon on your multimeter display? It might be indicating low battery which causes measurements to read much higher on some meters.

[Fastcast]

Re: Vizio GV42L help.

Tom, no it's just a cheap Cen-Tec meter from Harbor Freight. I did have another 9v battery laying around though and tested it, replaced the one in the meter and tested it also with the small battery setting on the meter and they both tested at 25mA.....so not sure what to make of that but both batteries did give a pretty good jolt also with the old fashion tongue test...lol

BTW....I'm getting the same readings with either battery, although neither is "new".

[tom66]

Re: Vizio GV42L help.

OK, are you setting the meter to the 200V/750V AC or the 20V DC setting? It should be on DC volts.

[Fastcast]

Re: Vizio GV42L help.

Ok, like the clueless idiot I'm am when it comes to this stuff, I had the multimeter at the wrong setting. Getting it set correctly 20V-DC...F2 is reading 5.1 and F1 is reading 11.87

These are some of my other readings.

U9...3.24 - 0
U7...3.24 - 0.2
U2...5.1 - 2.0
U8...5.0 - 2.0
U33...5.1 - 2.0
U3 (large)...11.87 - 5.0

[tom66]

Re: Vizio GV42L help.

It is an easy mistake to make . Luckily we figured it out quickly -- one member on here had me in circles because everything was doubled (except his plug socket) -- then we figured out it was on AC volts!

There are three pins, plus a tab pin (fat pin at the top) on the regulators. You want to test the outer two pins and the tab OR middle pin -- they are both connected together.

[Fastcast]

Re: Vizio GV42L help.

Ok Tom, the first figures I gave were the outer pins....Here's the tab readings.

U9...1.5
U7...1.0
U2...3.26
U8...3.28
U33...3.24

Thanks!

[tom66]

Re: Vizio GV42L help.

U7 immediately appears at fault as it should not be possible to go below 1.25V, these regulators have a minimum voltage. Please re-test it and note down the marking, it should be similar to AMC1117-xx where xx is "15", "18", etc. or "ADJ" or sometimes not present (which indicates ADJ.) If you can note down the same info for all of them but U7 looks to be faulty and it's unlikely for multiple ones to fail simultaneously.

[Fastcast]

Re: Vizio GV42L help.

Ok, retested U7...3.24 - 1.0 - 0.2

The markings are very tiny and very difficult to read but here's what I believe it says:

AMC1117.....that's it, than on a second line:
F0734J....maybe it's FO7341....can't say for sure.

Nothing seems unusual about U9 having an outer pin with no reading. 0.00?

[tom66]

Re: Vizio GV42L help.

U9 is good, I think. However, if you are concerned about it, you may replace it too. It is working if it ends in -15. The cost is about 50 cents per regulator, and replacement takes a few minutes.

You can replace U7 with this part:
http://www.digikey.com/product-detai...SCT-ND/1967218

[Fastcast]

Re: Vizio GV42L help.

Thanks Tom! A couple other things I noticed but not sure they're relevant?

U2, U7, U8 & U33....all have the same marking AMC1117-F0734J

U9 has a different marking K1117515-725 and looks slightly narrower than the others.

So U7 is the same part as U2, 8 & 33 but those are all reading higher volts.

I tried to search Digi-Key using the U9 part number (since it requires a different part) but I'm not getting any matches....How are you cross referencing because I can't get anything for the AMC1117 # either. lol

This TV has in the past given me problems on occasion where it will power on and it will have sound but no picture....I've just had to shut it off and power it back on, sometime several times to get the picture working. Do you have any thoughts on that or should I be considering repairing something else while I have this thing apart?

I do have a solder gun but will need to get some electrical solder. Is there anything in particular you recommend? A buddy of mine said I probably need to get a suction bulb from Radio Shack to suck up the old solder.

[tom66]

Re: Vizio GV42L help.

Thanks Tom! A couple other things I noticed but not sure they're relevant?

U2, U7, U8 & U33....all have the same marking AMC1117-F0734J

These are all adjustable regulators. The regulator output should be 1.2 - 1.3V higher than the 3rd pin (adjust), so:

U7...3.24 - 1.0 - 0.2 - faulty
U2...5.1 - 3.26 - 2.0 - working
U8...5.0 - 3.28 - 2.0 - working
U33...5.1 - 3.24 - 2.0 - working

U9 has a different marking K1117515-725 and looks slightly narrower than the others.

This is a 1117 type like the others but the key is the "15" in the part number, indicating 1.5V output, so it appears to be functioning properly.

So U7 is the same part as U2, 8 & 33 but those are all reading higher volts.

Yes -- this lowers the cost. The adjustable type output is set by an external resistor network, meaning only one regulator part is used on the majority of the board.

I tried to search Digi-Key using the U9 part number (since it requires a different part) but I'm not getting any matches....How are you cross referencing because I can't get anything for the AMC1117 # either. lol

"AMC" and "K" are just manufacturer codes. The key here is 1117 type, which indicates it is a positive low drop out regulator (LDO.) Here is the category for LDOs:
http://www.digikey.com/product-searc...2556290?k=1117

Here is the replacement for the 1.5V type, but I don't think you need it:
http://www.digikey.com/product-detai...SCT-ND/2121241

Notice this part is -slightly- different from the other part in the previous post.

This TV has in the past given me problems on occasion where it will power on and it will have sound but no picture....I've just had to shut it off and power it back on, sometime several times to get the picture working. Do you have any thoughts on that or should I be considering repairing something else while I have this thing apart?

I'm not aware that much about Vizios as they aren't sold in the UK. I do however know voltage regulators can be temperamental and show intermittent faults (such as unstable output voltage) before failing completely. I've had ones that'll work after a quick blast of freeze spray or a one hour drive in the car.

I do have a solder gun but will need to get some electrical solder. Is there anything in particular you recommend? A buddy of mine said I probably need to get a suction bulb from Radio Shack to suck up the old solder.

All you will need is a soldering iron, solder, and solder wick. See how someone else removes a regulator from a Vizio:
https://www.youtube.com/watch?v=cNFzBJELFoU&t=8m44s

He uses a powered solder sucker (nice bit of kit but pretty pricey) to get rid of the solder on the pads, but you can use solder wick.

[Fastcast]

Re: Vizio GV42L help.

Thanks so much Tom for all the info and taking your time!

[tom66]

Re: Vizio GV42L help.

I just hope you can fix it and save something from landfill. It is very satisfying .

[Fastcast]

Re: Vizio GV42L help.

Tom, just wanted to update that I did get the TV fixed. U7 was faulty just like you said.

It wasn't easy for an amateur, doesn't look real pretty and surprised I didn't smoke the motherboard but hey, it's working again!...lol

[tom66]

Re: Vizio GV42L help.

Great to hear!

[drumguy560]

Re: Vizio GV42L help.

I know this is an old, dead thread!

However, I just wanted to say thank you! This thread fixed my TV.

I was having an amber light, with no power, no matter what buttons you pressed.

It turned out to be U7 as stated in the latest posts on this thread.

Thanks!