vizio e321vl no 12v

[kevin.st56]

A friend of mine gave me a vizio tv e321vl and said they had a lightning strike and now the tv does not power on anymore.
Iv been doing a bit of reading on here and found a few things to test.
One thing is that the cable that joins the ps board to the main board, it does have the 5.2v standby, but it does not have the 12v. Being that its on the cold side, i grounded to the tv chasis.
As far as plugging in the tv, i notice that the vizio logo on the bottom front of the tv blinks amber momentarly, and then its off.
Is there anything on the ps board to test/measure?
Pic os ps board attached.

[CapLeaker]

Re: vizio e321vl no 12v

5.2VSB is always there, with the TV on or with it off. The 12V rail comes alive when the TV is on (PSon). The backlights come on when the BLon is present.
Have a look if the main board sends the two on/off signals or not.
Right now we need to know how you tested that TV exactly.
Other than that, you can disconnect the main board, take two 1k resistors and jump between 5.2vsb and the two on/off pins. When you plug the PSU in, all the rails should be up and the backlight on.

[kevin.st56]

Re: vizio e321vl no 12v

I only tested for the 5vsb to make sure that was live first, and it was.
I wasnt sure if the 12v was always live or not.
I will see if i can get my hands on some resistors since thats all in storage at the moment.

Edit: found my resisters, but all i have are 3 100k ohm 1/4 watt resisters.
Would putting those in parallel work?

[budm]

Re: vizio e321vl no 12v

With all the boards connected, what DCV do you have on that ON/OFF pin right next to the 12V pin?
The other ON/OFF pin is the BL-ON.
The 12V is generated from the same transformer of the STBY 5V.
Pictures provided by shopjimy.
Vizio/JVC 0500-0412-1300 Power Supply / Backlight Inverter E321VL JLC32BC3002

http://www.shopjimmy.com/vizio-0500-...-inverter.htm#

[kevin.st56]

Re: vizio e321vl no 12v

With everything plugged in, i get nothing on the on/off pin next to the 12v pin.
Iv also noticed i do not have the 5vsb with everything connected.
I do get the 5vsb when i unplug the 14 pin connector.
I just found a set of 10k ohm resistors that i can test jumping with, if it safe to use them.

[CapLeaker]

Re: vizio e321vl no 12v

So you plug the main board to the PSU and the 5VSB disappears? That contradicts your first post.

[kevin.st56]

Re: vizio e321vl no 12v

So you plug the main board to the PSU and the 5VSB disappears? That contradicts your first post.

when i tested for the 5vsb, that was with the 14 connector unplugged.
it wasnt until i was informed to test with it on for the on/off signal, and out of curiosity, i tested for the 5vsb with the connector plugged in, and i do not have the 5vsb on all 3 pins, nor was i getting anything on the on/off pin specified.
i have not tried the resistor jumper yet bec idk if the resistors i have would be too high of resistance for the test (1k ohm specified, but i have 10k ohm resistors).

[kevin.st56]

Re: vizio e321vl no 12v

An update...
Desided to use the 10k ohm resistors, and jumped the 5vsb to the on/off pins.
Backlight does turn on, and i do get about 11.6v on both of the 12v pins.
I did not leave the tv plugged in long at all since my resistors are much higher than specified to use, afraid of causing more damage if any.

What would be the next thing to test?
Would this mean the ps board is good, and an issue with the main board?

[dick_barton]

Re: vizio e321vl no 12v

The higher resistors are not a problem. If they were << 1K then you need to be more careful.
With the set off and the power supply disconnected from the mainboard find out which pins from the power supply connect to the 12V's and 5V's on the main board and measure the resistance from those points to ground and see if you have a short or very low resistance on the main board.

[kevin.st56]

Re: vizio e321vl no 12v

All. The 5v gave me 1.2k ohm each.
All the 12v gave values in M ohm, but their values slowly decline without stopping. Started around 10M and has gone down to 2M. After waiting a minute, then its back up to 14M.
These are all measured with the main connector unplugged.

[dick_barton]

Re: vizio e321vl no 12v

So these are the readings taken off the main board, not the power supply. If so then there does not appear to be a low resistance on the main board supply inputs so I cannot see why you would lose the 5V standby on the power supply with the mainboard connected.

[kevin.st56]

Re: vizio e321vl no 12v

Yes, tests were done on the mainboard itself with the connector unplugged.
Did the same thing with the on/off pins on the mainboard. The on/off pin right next to the 12v pin is showing very low resistance. The other on/off pin shows 1.2k ohm.

[dick_barton]

Re: vizio e321vl no 12v

How low?
But the 5V standby supply input to the main board is not a problem so I cannot see why are you losing the 5V standby when you connect the main board to the power supply

[kevin.st56]

Re: vizio e321vl no 12v

Anywhere from .1 to .3 ohm

[dick_barton]

Re: vizio e321vl no 12v

I would suspect that is a problem. Can you post some photo's nice and sharp of the main board.

[kevin.st56]

Re: vizio e321vl no 12v

Sure. Lighting is somewhat poor, and camera flash overpowers the camera and makes glare
Ill post my several attempts lol
Taken at 13mp

[dick_barton]

Re: vizio e321vl no 12v

With the set off and power supply disconnected using your meter on ohms can you check what resistance to have between P_On and each of the pins of Q1

[dick_barton]

Re: vizio e321vl no 12v

Thinking about it if the P_ON signal comes directly from the main processor then the main board may well be trashed.

However there is a possibility that the processor switches one of the 3 legged devices (transistors/mosfets) to provide the P_On voltage which may have gone short circuit.

Without a schematic it is hard to tell what is going on but may be worth your while doing an ohms check on all the 3 legged devices looking for a short circuit.

I think they are marked Q..

[kevin.st56]

Re: vizio e321vl no 12v

With the set off and power supply disconnected using your meter on ohms can you check what resistance to have between P_On and each of the pins of Q1

Where are these located?
Im having difficuly locating them

Edit: found q1. What order of pins should i check?
Edit 2: nvm, was looking at Q14.

[dick_barton]

Re: vizio e321vl no 12v

Test the ones that look like Q1. Use your meter and test all 3 pins. Just use your meter and go around the three pins in turn looking for a short circuit.