Vizio VO320E Bad Power Supply Board?

[tom66]

Re: Vizio VO320E Bad Power Supply Board?

OK, do you wish to repair the PSU or just swap it?

[alja]

Re: Vizio VO320E Bad Power Supply Board?

I'm learning and enjoying it. If you could guide me I'd love to fix it!

[tom66]

Re: Vizio VO320E Bad Power Supply Board?

OK, do you see any output labelled 24V, or another voltage different from 5V or 12V?

[alja]

Re: Vizio VO320E Bad Power Supply Board?

nope, only 5v and 12v

[Kylum]

Re: Vizio VO320E Bad Power Supply Board?

I'm sure that you did but make sure that the PSU is completely isolated from the other boards when testing the voltage output of the PSU not just the main board.

[tom66]

Re: Vizio VO320E Bad Power Supply Board?

Can you check the voltage across this capacitor? Be very careful not to let the probes slip. You are working on the high voltage primary side of the power supply, which carries an electrocution risk.

The voltage should be checked in standby (logo orange) and switched on (logo white) with the other boards connected up.

The only loads connected to this appear to be the main board. The inverter is built in, using high voltage driven design.

[alja]

Re: Vizio VO320E Bad Power Supply Board?

Do I measure this with the meter in DC?

[tom66]

Re: Vizio VO320E Bad Power Supply Board?

Yes, sorry for not clarifying.
Expect 160~170V in standby, and around 400V in operation.

[alja]

Re: Vizio VO320E Bad Power Supply Board?

No problem, I test it with the meter in DC at 1000 and the reading were the same for stand by (amber logo) and on (white logo) at 175v-176v I also had all the board connected

[tom66]

Re: Vizio VO320E Bad Power Supply Board?

OK, this indicates a PFC fault.

Across the red ringed capacitor please measure the voltage across it. Expecting 10V to 25V.

For the blue area, please post a picture of under the heatsink the best you can.

[alja]

Re: Vizio VO320E Bad Power Supply Board?

ok, the measure was 20v standby and 22 ON. About the picture, do I need to remove the heatsink? or the best I can without removing it

[tom66]

Re: Vizio VO320E Bad Power Supply Board?

Is it closed off on both sides? Can you see anything under it?

[alja]

Re: Vizio VO320E Bad Power Supply Board?

well here the pics I could take, I think they cover pretty much everything under it but let me know if you need a specific area.

[tom66]

Re: Vizio VO320E Bad Power Supply Board?

OK, all I need to see was the PFC coil, which is there. So it confirms this board does use PFC.

At this point, can you remove the power board and take a picture of the bottom of it? The green side of the circuit board.

[alja]

Re: Vizio VO320E Bad Power Supply Board?

Here the best I could, I hope is clear enough, if not I could split it to give you more sharpeness

[tom66]

Re: Vizio VO320E Bad Power Supply Board?

Please test this diode.

To test: Power supply UNPLUGGED. Multimeter must be set to diode test mode. Red probe goes on one end, black on the other. Record reading. Then reverse probes, and record the reading.

Expecting: 400~800 one way, open circuit (usually shown as "1") the other way.

[alja]

Re: Vizio VO320E Bad Power Supply Board?

The reading is the same in both ways 0.01. board unplugged from the outlet and other boards

[tom66]

Re: Vizio VO320E Bad Power Supply Board?

Nice! First check and it's a dud. Pull it and test it out of circuit to be sure, but you've probably found the fault. Replace that diode with a new part... read the part # off it and go to digikey.com to find a replacement. (Do not just use one that looks the same size... )

[alja]

Re: Vizio VO320E Bad Power Supply Board?

wait, I measure the other diode that is next to this one the D802 and gave me the same reading both way, .001 starts at 500 but ends at .001, is it bad too? so I need to replace it?

[tom66]

Re: Vizio VO320E Bad Power Supply Board?

That diode being bad will make the other look bad too, because they're effectively in parallel (except one goes through an inductor, forming part of the boost converter circuit.) To be sure you can remove both from the circuit and test them, but it's much rarer for that other diode to fail and it usually only causes slightly higher standby power consumption (and no other bad effects.)

Actually you can also just lift one leg of each so they stay on the board and you know which is which.