Vizio VW37LHDTV10A no backlight

[Brian with a/b]

Hi! Well, the orange standby light comes on and changes to white on power up. I can't see any backlights at all. The PS board fuse checks good as well as the two SMD type fuses near J1. The unit will power off, making me think it may not be a U33 failure. All the mainboard caps are Tiacon and CE3 has a corroded cap. My question is, should I pull the mainboard and replace the cap OR check more voltages before continuing? Noob question, sorry.

[budm]

Re: Vizio VW37LHDTV10A no backlight

Pictures of the whole back side of the TV and the boards.
We need to find out if we have 24VDC, BL_ON signal or not.

[Brian with a/b]

Re: Vizio VW37LHDTV10A no backlight

Ok. Here we are. Thought it was unusual that the "CPU" had no heatsink.

[budm]

Re: Vizio VW37LHDTV10A no backlight

So you need to check the signal pins on the power supply board when TV is OFF and when TV is turned on:
PS_ON pin.
A pin
B pin
C pin

[Brian with a/b]

Re: Vizio VW37LHDTV10A no backlight

Sorry for the slow reply. In standby they all read zero, ON they were PS_ON 3v, A 2.6v and B .03v ; as far as I can tell.

[Brian with a/b]

Re: Vizio VW37LHDTV10A no backlight

Also, none of the pins on the 24vdc plug read anything close to 24vdc.

[budm]

Re: Vizio VW37LHDTV10A no backlight

Also, none of the pins on the 24vdc plug read anything close to 24vdc.

What do you get?

[Brian with a/b]

Re: Vizio VW37LHDTV10A no backlight

1.5vdc

[budm]

Re: Vizio VW37LHDTV10A no backlight

OK, we need to find out if the PFC Voltage booster circuit is working or not next.
You will have to be real careful since you will be making measurement in the deadly PRIMARY side of the circuit. You will be measuring the Voltage RIGHT AT THE TWO LEGS OF THE MAIN FILTER Cap, it is the big cap laying on it side, it should have about 160VDC when the TV is not turned on and then it should jump up to >360VDC when power switch is activated and the main board sends out the PS_ON to turn on the PFC Voltage booster circuit and the 12V/24V Power supply section.
Do not let your hands or body touch anything on the board.

[Brian with a/b]

Re: Vizio VW37LHDTV10A no backlight

167 in standby, 165 with power on.

[budm]

Re: Vizio VW37LHDTV10A no backlight

OK, that is why you are not getting the 12V/24V because the 12V/24V power supply section requires that boosted Voltage to run.
You may want to look for another power supply board from shojimmy at this point, to fix to component level is not going to be easy dealing with SMD parts.
Beside this power supply board, we do not know if all the regulators ICs are all good or not on the main board until you get the power supply running first.

Power supply:
http://www.shopjimmy.com/vizio-0500-...upply-unit.htm
He is having 5% of for December.

[Brian with a/b]

Re: Vizio VW37LHDTV10A no backlight

Alrighty then, I will get a PS. Thanks for the help, Mr. BudM.

[Brian with a/b]

Re: Vizio VW37LHDTV10A no backlight

I replaced the power supply board and it's doing pretty much the same thing as before. Any ideas?

[budm]

Re: Vizio VW37LHDTV10A no backlight

PS_ON is still at 3VDC? The voltage on the main cap still did not go up to >360VDC?
Did you get the board from SJ?

[Brian with a/b]

Re: Vizio VW37LHDTV10A no backlight

Yes, still 3vdc, no change on main cap, Ebay

[Brian with a/b]

Re: Vizio VW37LHDTV10A no backlight

Got one coming from SJ.

[Brian with a/b]

Re: Vizio VW37LHDTV10A no backlight

The one from SJ isn't working either. The power board is not the problem.

[nomoresonys]

Re: Vizio VW37LHDTV10A no backlight

ok, did you try just unplug the connector for bl-on, see if the backlights come on?

[nomoresonys]

Re: Vizio VW37LHDTV10A no backlight

go ahead n change the corroded cap, what can it hurt?

[budm]

Re: Vizio VW37LHDTV10A no backlight

If you have PS_ON but no boosted Voltage on the main cap, then the power board is still not right, there is nothing else that the power supply will need to get the boosted voltage.
You can run the power supply board by itself and use force on signal on the PS_ON pin.
http://s807.photobucket.com/user/bud...?sort=3&page=1