VIZIO VO47L FHDTV10A - Voltage Regulator Input

[gethooked]

Hi all.

- Why would my TV be functioning properly if I have more output than input on the transistor?

- Why would my TV be functioning properly I have hardly any volts on the U3 regulator?


U3
AZ7805T - Regulator
E1 744J60
pin 1 = 2.44 (Input) - Should be 12V0.000 (Ground)
pin 2 = 0.000 (Ground)1.02 (Output) - Should be 5V
pin 3 = 1.02 (Output) - Should be 5V



O27
C5886 - Transistor
7x
pin 1 = 11.8 (Adj)
pin 2 = 11.8 (Output)
pin 3 = 2.44 (Input) - Should be 12V

F1 & F2 Fuses-

Both the (5V and 12V) fuses on the main-board have correct power on both sides of the fuse.

I'm afraid to put the set back on the wall with these readings.

[budm]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

"U3
AZ7805T - Regulator
E1 744J60
pin 1 = 0.000 (Ground)
pin 2 = 1.02 (Output) - Should be 5V
pin 3 = 2.44 (Input) - Should be 12V"
OK, going by the pictures of U3 7805 regulator
Pin 1 (left) is the Input pin
pin 2 (middle, also connected to the mounting tab) is Ground
pin 3 (right) is the Output pin.

https://www.flickr.com/photos/76588390@N03/6949210094/
So if you check the resistance between pin 1 and the 12V fuse, it should show <1 Ohms (excluding the probes resistance).

[gethooked]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

It looks like .4 (if I did it correct)
My multimeter did beep with the continuity test.

I also revised my pin output in the original post from the link you shared

[budm]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

if it is 0.4 Ohm between the 12V fuse and the input pin of 7805, then it must have 12V at the input pin, so it has to be error some where.
Are you sure it is 0.4 Ohms, not 0.4 K Ohms or 0.4M Ohms?
So right now we have voltage drops about 10V some where beteen the 12V fuse and the input of the regulator.

[gethooked]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

0.45 K ohms

0L Ohms

Positive lead on Input Pin 7805 and negative lead on 12V fuse.

[budm]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

So the reading is 0.45K? or OL?

[gethooked]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

0.45k (With the set OFF)

[budm]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

Well, then we need to trace out the connection from input pin to where it goes, there may be a ferrite bead (FB) or a small inductor in the that path of the circuit.

[gethooked]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

Where would I begin, bud?

[budm]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

Just put the meter in Ohms mode, one probe on the input in of U3, then look at the trace that is connected to the Input pin of U3 and start probing that trace with another probe, if you are on the correct trace then the meter should show <1 Ohms, it will be time consuming process but that will be the way to do it unless you have the main board diagram.

[gethooked]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

I cannot locate the diagram online, so I will just have to try and probe the trace.

I've never traced before, so this should be interesting.

Power off?

[budm]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

"Power off?" unplugged.

[gethooked]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

I cannot locate the break.

I just do not understand why the TV is even functioning flawlessly without the 5V on the output of that regulator.

How can there be only 2.44V into the transistor and ~12V out??

[gethooked]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

bud,

I remember touching the input pin and ground pin together on the 7805 Regulator when I first tested the board a week ago. It shorted and shut the TV off, but still powered on.

I was never able to see if the regulator ever had 12V into it, because i shorted it.

Would this cause the regulator to not accept the 12V in?

I bought another regulator, would it be worth soldering the new one in?

[budm]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

The 5V output may not be required for certain function of the TV to work. You may have to try ALL modes of operation of the TV to find out which function does not work. The 12V is used for the audio amplifiers and audio circuit. I have a feeling that there is an inductor in series with the input of the regulator, so when the input shorted to ground that inductor is damaged. You can try another IC just in case the input is damaged sine there is no protection diode between the input and output to protect it from input short situation. See page 11.

[gethooked]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

These are the regulators I purchased. Will these work?

http://www.digikey.com/product-searc...ader=search_go

http://www.digikey.com/product-searc...ader=search_go

If this is the correct replacement, I will go ahead and replace this regulator and report back.

Thanks again for all your time and knowledge, bud!

I have learned a ton by trying to fix this myself and from these forums.

[Alastair E]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

If the set is Working--Why are you potching with it?

There's a saying--

If it Aint Broke--Dont Fix It!

[gethooked]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

Hi Alastair.

My TV wouldn't power up.

See here:

https://www.badcaps.net/forum/showthread.php?t=40997

I replaced busted capacitors and fuses and the TV works great now (at least the HDMI that I tested so far).

While I still have the TV apart, I wanted to test the regulator that I shorted when I first starting working on finding the culprit(s).

I agree with you, but now I am just trying to make sure I do not put the set back on the wall and cause more damage because I didn't repair the 12V issue I'm having.

[gethooked]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

Diode D96 has .45K Ohms in both directions.

Could this be the culprit?

[budm]

Re: VIZIO VO47L FHDTV10A - Voltage Regulator Input

Is one end of that Diode D96 connected to the input pin of U3, and the Anode of that Diode D96 connected to the 12V fuse?