Vizio M602i-B3 No Backlights

[landyboy]

Ok ,made an assumption on this one that led backlights were bad so I took apart and tested every strip, no bad LED's. Put back together and started testing. On the LED pins on the power board I have 15v with lights plugged in or without. Bad power board?

[budm]

Re: Vizio M602i-B3 No Backlights

That is just power supply board, the LED driver circuits are on the main board.
You need to upload pictures of the whole back side of the TV showing all the boards.
There are more than one version of this model.
https://www.shopjimmy.com/catalogsea...Vizio+M602i-B3

[landyboy]

Re: Vizio M602i-B3 No Backlights

Pics added

[budm]

Re: Vizio M602i-B3 No Backlights

It looks like it have many many LED strings used in that panel.
So does the backlights even flash on for seconds at all?
Did you take the pictures of the LED strings?

[landyboy]

Re: Vizio M602i-B3 No Backlights

They do not flash at all. There are a lot of strips. I wish I would have taken a pic but I did not.

[budm]

Re: Vizio M602i-B3 No Backlights

This is going to be tough because we need to find out if the LED driver circuits are getting the BL-ON signal or not.
The power supply board does have all the output Voltages, correct?
And you can also turn the TV on and OFF OK, correct?

[budm]

Re: Vizio M602i-B3 No Backlights

https://www.badcaps.net/forum/attach...2&d=1537849060
What DC Voltage do you have on the + legs of those two caps? 15V?
The filter caps (C313, 314, 315, and C321) for the LED power supply are rated at 35VDC so 15V output may be low, I expect the supply Voltage to be around 20V or so.
Power supply board: https://www.shopjimmy.com/vizio-09-6...led-board.htm#

LED strips:https://www.shopjimmy.com/vizio-e600...-16-strips.htm
That is what you have, correct?
It has 16 strips (8 LED's per strip), each strip has two LED strings (4 LED's per string), and the LED drivers have 32 MOSFET's, one per strings, so the Vf of each string will be about 12V + Vdrops on the MOSFET and the current sensing resistor, so it should have about 20V or so on the LED power supply (it uses synchronous rectification) .
So the problem looks to be on the power supply board.
Check the DCV between the two legs on any one of the two 450VDC filter caps to see if it has close to 400VDC when TV is turned on.

[landyboy]

Re: Vizio M602i-B3 No Backlights

yes all other output voltages seem correct.

[landyboy]

Re: Vizio M602i-B3 No Backlights

Pos legs on Caps 313,315,315,321 15.39 on each

Filter caps 378vdc

[budm]

Re: Vizio M602i-B3 No Backlights

I believe that is too low, I expect about 20Vdc or so.
378vdc is OK.

[landyboy]

Re: Vizio M602i-B3 No Backlights

I ordered a power supply, we will see what happens. I do not see a pin marked BL-ON anywhere on the board. which pin tells the Backlights to turn on?

[budm]

Re: Vizio M602i-B3 No Backlights

Since the LED drivers circuit are integrated into the Main board, so there is no BL-ON pin that usually goes to the power supply/LED driver board like typical TV.

[landyboy]

Re: Vizio M602i-B3 No Backlights

Got the new power board, at first appeared nothing changed. I then turned the lights out in the room and the backlights were on. So they may have been on before. The screen is completely black. I can not see a image with a flashlight. I disconnected the Tcon one side and the screen turned a dark blue. I'm thinking I have a completely different issue?

[budm]

Re: Vizio M602i-B3 No Backlights

Put the old power board back in place then and see of the backlights are on or not.

[landyboy]

Re: Vizio M602i-B3 No Backlights

Yes they do, I guess I should have done that first.

[budm]

Re: Vizio M602i-B3 No Backlights

You can see the backlights through the holes on the back of the LCD panel assembly unless your room lights are really bright.

[landyboy]

Re: Vizio M602i-B3 No Backlights

I have it face down in my workshop. I can see them with lights on but they are not as bright as some sets I have seen I will take a pic.

[landyboy]

Re: Vizio M602i-B3 No Backlights

Pics, I don't think they are as bright as they should be?

They are the same with both Power Moards

[landyboy]

Re: Vizio M602i-B3 No Backlights

In the dark the screen is very lightly lit with no image at all.

[budm]

Re: Vizio M602i-B3 No Backlights

BTW, the new power board also puts out only 15V too?
What does the screen look like if T-CON board not connected?