Vizio E470VL no power, logo not lit

[chknjdn]

Hello all, I have a TV that I am trying to repair. It is a Vizio E470VL. I got it used and the previous owner told me that it had just quit working and he thought it would probably just be a fuse or something.
I have tried powering it on with no effect. It doesn't click nor light up the logo on the front. I opened it up and checked the fuse and it is fine, 0 ohms. I looked at all the caps on the power board and all of them seem to be good. I have been checking some voltages on the power supply board. With the main board connected I get 0.0 volts for all of the outputs of the board to the main board. I have powered it up with the main board connector disconnected and then I get +5 volts to the three pins that are marked +5, 0 volts on the +12 pins, and also 0 volts on the standby pin.

I think that the standby power is what I am missing. I am not sure where on the board to begin checking for it. below are some pictures of the board in question.

Thanks for any suggestions you can offer.

Chuck

[budm]

Re: Vizio E470VL no power, logo not lit

So right now the 5V STBY power supply is working to supply the main board, when the power switch or the the power button on the remote is activated, the main board will send out the signal to the STANDBY (or PS_ON) pin on the power supply-inverter combo board to turn on the power supply. The main board will also send the ON/OFF (or BL_ON) signal to turn on the backlights inverter circuit.
So right now the problem in in the main board some where. There are two white fuses on the main board and voltage regulators that need to be checked.

[chknjdn]

Re: Vizio E470VL no power, logo not lit

I'm confused, my previous reading led me to believe that the standyby pin should have +5 volts on it all the time, when it is plugged in. Then the main board would send a signal to the power supply board to turn on the other +5 and +12 sections when the power on switch was depressed. Below is a close up of the connector on the power supply board with the pinout next to it.

I will try to check the VR on the main board. All three fuses on the main board are good.

Thanks,
Chuck

[tom66]

Re: Vizio E470VL no power, logo not lit

So, you get +5V with main board disconnected, but it is disappearing when you plug in the connector?

[chknjdn]

Re: Vizio E470VL no power, logo not lit

That is correct. When the power supply is not connected to the main board, there is +5 volts on the three pins on the left of the connector. When the power supply is connected to the main board, there is no voltage on any of the pins.

Thanks,
Chuck

[tom66]

Re: Vizio E470VL no power, logo not lit

It sounds like the main board has a short on the 5V. You can either swap the main board or try to locate the short. Some methods to do this are discussed here: https://www.badcaps.net/forum/showthread.php?t=31683

[chknjdn]

Re: Vizio E470VL no power, logo not lit

After removing the board to try to chase down the short, I noticed on the underside of the board that one of the capacitors is missing. I will attach the picture I took of it. There are no marks on the board around it, but I wonder if it could be the result of whatever component shorted. I also took a picture of the top side of the board oposite it.

It was C510. Not sure what size it might have been as it's SMT.

Thanks,

[tom66]

Re: Vizio E470VL no power, logo not lit

May indicate the TV has been dropped at some point, which can cause some capacitors to short.

Before you trace & repair try this jumper to check screen OK.

Connect 5V standby to PS ON through 100 ohm resistor, and to BL ON through 100 ohm resistor too. Connector should be disconnected from main board. Backlight should light and you will be able to see if panel is OK.