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TV Repair - Accidentally brought back to life (momentarily) with a DMM!

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joshsstuff

New Member
I was probing voltages on the pins of the TVs Logic board (going to the Time-Control Board) and suddenly it came to life!
The power supply did not sound healthy to me, but maybe I'm mistaken.
I'm trying to get the video uploaded to listen to the sound it makes.

After I power cycled the TV it was was dead once again and I could not reproduce the probing that brought it to life.

Specs:
Vizio LED TV E70u-D3 (70")
Info PDF https://support.vizio.com/s/article/E70u-D3-Model-Information?language=en_US

Original Problem:
It was reported to me that the TV became increasingly unstable.
It would turn itself off after just a few minutes, and there was distortions on the screen.
Finally the TV would display nothing at all.
The power cable was replaced, and the TV was power cycled. Both attempts seemed to correct the problem, however now the white power LED will illuminate for a few seconds and go out after a minute, there is no longer any display shown on the screen.

Trouble shooting Technique.
I intend to check all the power supply capacitors, then move to stand by power, voltage regulators, and voltage levels on other boards.

The red label "12.3V" is the pin I was probing when the TV came to life.



With the TV plugged in, but in stand by mode, there is 0volts on these pins, however after the power button is pressed 4/7 of them get 12.3 volts.
I was checking this when all the sudden the power supply booted up (noisily) and the screen lit up.
I was able to feed a signal into the TV, and it displayed it just fine (just a noisy power supply to my ears)


The 2nd photo shows my diagnostics of the Power Supply.
Pin 13 labeled "PS-ON" has 0 volts in standby mode and 5v when the power button is pressed.
The voltage is persistent on this pin, however the "power" led only stays lit for about 5 seconds before fading out. After witch you can again power it on for a brief time.

I am not sure if the power supply quality is the underlying issue, or if there is a fault on the main logic board.
Can anyone suggest how I can test this?

Thanks!
 

JimB

Super Moderator
Most Helpful Member
Your pictures are not displayed, put them here on ETO using the Upload a File button at the bottom right hand corner of the screen.

JimB
 

Pommie

Well-Known Member
Most Helpful Member
The pictures are displaying fine for me so it may be a dropbox problem. Better to upload them.

Mike.
 

joshsstuff

New Member
Your pictures are not displayed, put them here on ETO using the Upload a File button at the bottom right hand corner of the screen.

JimB
The pictures are displaying fine for me so it may be a dropbox problem. Better to upload them.

Mike.
The pictures come up on my screen and I checked with both Chrome and MS Edge browsers.
Do I need to add a post with the pics uploaded?
 

joshsstuff

New Member
I suspect the capacitor values will be on the opposite side of the caps.
You are right, they were, they are 25v 1000uF & 450v 100uf respectively.
I started removing and testing capacitors:

I won't have access to a proper ESR meter for a few days. In the mean time this is the best I have:

The reading fluctuates between 0.016 Ohms and .31 when I first took it out (maybe too hot?)
 

picbits

Well-Known Member
Make sure you discharge any capacitors before using a tester - they can hold a nasty charge. Those cheap testers aren't bad to be honest with you - good for a "yes or no" answer on a capacitor. 0.31R is pretty reasonable for a 450v capacitor.
 

picbits

Well-Known Member
I would also check all soldered joints for a "dry joint" - it could be that when you were probing, you put pressure on a dry joint and it made contact again.
 
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