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Old 06-19-2018, 10:54 AM   #61
R_J
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

A scope would be better, Try heating just one transistor at a time using the tip of your soldering iron, just place it on for a second or two is all that should be needed, then try it on the ic.
Using a heat gun heats too wide an area to pinpoint the problem,

It could even be a bad feedthru connecting the two sides of the board. Like this one... It looks corroded, green, it should be copper colored like the others. it may have corroded the connection to the other side of the board, but when heated the copper expands and makes connection.
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Last edited by R_J; 06-19-2018 at 11:02 AM..
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Old 06-20-2018, 05:53 AM   #62
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

Quote:
Originally Posted by R_J View Post
A scope would be better, Try heating just one transistor at a time using the tip of your soldering iron, just place it on for a second or two is all that should be needed, then try it on the ic.
Using a heat gun heats too wide an area to pinpoint the problem,

It could even be a bad feedthru connecting the two sides of the board. Like this one... It looks corroded, green, it should be copper colored like the others. it may have corroded the connection to the other side of the board, but when heated the copper expands and makes connection.
Thanks R_J. I found a total of 4 feedthru holes that were corroded. I cleaned them up as best as I could and they all tested good for continuity from one side to the other.

Won't the soldering iron melt the transistors and the ic?
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Old 06-20-2018, 11:22 AM   #63
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

In some cases the transistor is soft plastic but they can usually handle it, just touch the iron to a corner and if it melts you can't do it. If the iron is adjustable turn it down.
If its a transistor, you could apply the iron to the collector pin (with power off) this would heat the transistor without touching the plastic.
as for the corrosion any idea where it came from? it could be electrolyte from a leaked cap that caused it. If you cleaned them up you could also apply some solder, that would fill the feedthru and be more reliable.
I see two electrolytics in that area, if you did'nt replace them, try switching them around and see if it changes anything

Last edited by R_J; 06-20-2018 at 11:25 AM..
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Old 06-20-2018, 12:21 PM   #64
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

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Originally Posted by R_J View Post
In some cases the transistor is soft plastic but they can usually handle it, just touch the iron to a corner and if it melts you can't do it. If the iron is adjustable turn it down.
If its a transistor, you could apply the iron to the collector pin (with power off) this would heat the transistor without touching the plastic.
as for the corrosion any idea where it came from? it could be electrolyte from a leaked cap that caused it. If you cleaned them up you could also apply some solder, that would fill the feedthru and be more reliable.
I see two electrolytics in that area, if you did'nt replace them, try switching them around and see if it changes anything
I have no idea where the corrosion came from. I had thought about filling them with solder, but I don't know if I can, because of how small of an area these holes are in. About half the size of a pin head. I may give it a try anyway.

Yes, the 2 caps that you are talking about are new ones.

Thanks
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Old 06-20-2018, 04:54 PM   #65
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

I have seen intermitint feedthru's in the past and it can be a real pain to find a problem, It may not be the problem in this case though.
If you have some flux that would help but usually capillary action will draw the solder into it.
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Old 06-23-2018, 01:43 PM   #66
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

Ok, I heated each transistor and the VGA chip. I even removed and tested the one transistor, Q29 circled in yellow on the picture, and the diode D99 circled in orange. I left the transistor out of the circuit and was able to get the TV to operate after heating the whole corner area again. The only thing that leaving that transistor out did was prevented the logo light from turning white like you thought it would do, R_J. I even thought that maybe the solder joints were bad on the receiver for the manual control plug, so I reset the solder on those pins. Wow, my eyes hurt now.

Finally, I decided to check the regulator voltages again on U29, circled in red. Everything was the same as it was before whether the TV was working properly or not. Pin 1=.54v, Pin 2 and the base=1.79v, and Pin 3=3.34v. I heated the regulator with a piece of keystock that I heated with a butane torch. I was able to turn the TV on and have it operate properly. I tried this several times letting it sit for an hour in between each try and it turned on every time. I had to make the regulator pretty hot to get the TV to turn on and stay on. Could this actually be the problem? Does this make any sense? Could it have anything to do with the thermal protection in the regulator?

I'm having a problem figuring out a match for this regulator on digikey. If you think this could be the problem, could you help me pick the correct one to order?

Thanks R_J for all your help!
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Old 06-23-2018, 03:24 PM   #67
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

Did you ever replace CE16, it is on the input to that ldo, Not sure if digikey carries that ic, ap1084kla
I guess the closest from digikey would be LT1084IT#PBF-ND although it is in a to220-3 and not a to263-3

Last edited by R_J; 06-23-2018 at 03:55 PM..
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Old 06-23-2018, 03:40 PM   #68
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

Yes, I replaced CE16.
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Old 06-23-2018, 03:57 PM   #69
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

Would this one work?

https://www.digikey.com/product-deta...ICT-ND/2122993
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Old 06-23-2018, 04:04 PM   #70
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

Yes that one should work

LM1084ISX-ADJ/NOPBCT-ND

https://www.digikey.com/number/en/te...&bpn=296-11272

Last edited by R_J; 06-23-2018 at 04:07 PM..
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Old 06-24-2018, 08:14 AM   #71
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

R_J, is it possible for this regulator to be the problem even though it is showing good voltages?
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Old 06-24-2018, 09:12 AM   #72
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

Yes, they can oscillate causing noise on there output, usually the caps take care of it. They supply data circuits so it does'nt take much to corrupt the data. This is where one would use a scope to see whats going on with the output.
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Old 06-27-2018, 10:56 AM   #73
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

Well I just received the regulator from digikey. This one is quite a bit smaller in size than the one I removed. I got it soldered in and there is no change in the TV operation. I will update when I get a chance to figure anything else out.

Last edited by ken_taz; 06-27-2018 at 10:58 AM..
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Old 06-29-2018, 01:01 PM   #74
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

I heated a piece of keystock with a butane torch and heated the new capacitor that I put in CE16 with the hot keystock. I made it hot enough to melt the jacket on the top of the cap (Can you say frustrated). I figured that I tried everything else in this area, why not? The Tv has turned on normally now for the last few days without heating anything anymore. Make sense? Not to me!
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Old 06-29-2018, 04:44 PM   #75
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

I checked the manual and found this. I would change CE16 to a 470uf see if that helps. The boards that use the 1000uf also have the coil and diodes which are not used on this board.
Where did you get the replacement cap?
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Last edited by R_J; 06-29-2018 at 04:48 PM..
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Old 06-30-2018, 05:22 AM   #76
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

I got the capacitor at Radio Shack. 220uf 35v to replace the 220uf 25v.

The Tv wouldn't tun on this morning without heating the CE16 220uf cap. It was a bit cooler in my garage this morning and I figured it wouldn't turn on because of that.

So 470uf 25v?
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Old 06-30-2018, 11:05 AM   #77
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

give it a try, I know without a scope it is kind of trial and error to find the problem.
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Old 07-09-2018, 06:47 AM   #78
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Default Re: Vizio VW42L FHDTV10A will not turn on without unplugging and plugging TV back in

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give it a try, I know without a scope it is kind of trial and error to find the problem.
Okay. I figured that just maybe the new cap from Radio Shack that I used was defective, since it seemed to work fine when I would heat it up first. I ordered 220uf and 470uf caps from digikey just in case the new 220uf didn't change anything. I had to wait for a cooler morning to finish testing. I got the garage down to 65 degrees overnight. The Tv fired up fine and stayed on with no popping or buzzing. It seems to have taken care of the problem.
https://www.digikey.com/product-deta...5CT-ND/6109603

Thanks R_J
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