Vizio SV470XVT1A LCD Power Supply Help.

[dolivas27]

I have a Vizio SV470XVT1A 47” LDT TV with a DPS-379AP power board.

The board has the 5VSB and that's it no 12V or 24VI the Vizio logo on the front light orange.

I have removed every Capacitor and tested it with an ESR Meter they all test good.

All diodes, Resistors, MOSFET test good.

I am new to working on the SMPS so kind of need some direction on where to start testing really wish I could find a schematic for the power supply but I don't think they exist.

The main filter cap has around 170v DC on it.

Let me know what else you need and I will provide it ASAP.

Thanks,
Dean

[ammarben]

Re: Vizio SV470XVT1A LCD Power Supply Help.

power supply alone jump PSON to 5VSB

[budm]

Re: Vizio SV470XVT1A LCD Power Supply Help.

Check the DCV on the PS-ON pin to find out if the main board is sending the turn on signal to turn on the PFC and the rest of the power supply or not.

[dolivas27]

Re: Vizio SV470XVT1A LCD Power Supply Help.

There is no DCV on the PS-ON.

I will jump the 5VSB to the PS-ON when I get home later this evening.


Thanks for the help.

[budm]

Re: Vizio SV470XVT1A LCD Power Supply Help.

Make sure you disconnect that PS-ON wire going back to the main board first otherwise you can damage the switched transistor (which is normally ON) on the main board if there is no buffer resistor on the Collector of the transistor on the main board.

[dolivas27]

Re: Vizio SV470XVT1A LCD Power Supply Help.

Ok I jumped the 5VSB to the PS-ON Pin only thing connected to the power supply was the AC line and the power supply now had the 12V & 24V so it looks like the main board is not providing the PS-ON.

I will investigate more this evening.

[dolivas27]

Re: Vizio SV470XVT1A LCD Power Supply Help.

Ok so the power supply look good.

I put it back in the tv and then removed the cover to the main board to check it out. I first check the fuses on the main board and they all tested good. So I plug it in to test the regulators on the board and when I moved one of the wires I here the power supply click on. Hmmmm look at the screen and the TV is now on and working.

So I finish checking the regulators and tried moving the wires again to get it turn off or not turn on again and it seems to be working ok.

So I go to turn it off again and it would not turn off so I pull the power plug and try to turn it back on again and it works fine on and off.

So I left the TV unplugged all night and this morning plug it in and try to turn it on and it will not turn on again.

I am going to pull the main board out this even to look for cold solder joint and check the caps they all look good but that does not mean there not bad.

Does anyone know if there is a common problem with the main board in this TV?

[Agent24]

Re: Vizio SV470XVT1A LCD Power Supply Help.

A common problem with some Vizios seem to be bad\corrupt(not sure which) EEPROMs, but AFAIK the symptoms are not intermittent in that case.

You say it came up when you moved the wire - have you checked the wiring is OK? Maybe the contacts are loose or something.

Did you check the regulators again when it is not working?