Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

[Naturallyk2]

Symptoms: As soon as I plug it into the wall, the TV turns on for 3 seconds and then shuts off. The TV backlights do not come on. The Vizio standby light illuminates orange, but will turn off when the rest of the TV turns off. The TV will not turn itself back on nor will the Vizio Standby light illuminate.

Troubleshooting: I've inspected the PS and found no visible signs of blown caps or damaged components. I've inspected the other boards including the inverter boards and have found nothing visible either. I've disconnected the inverter boards, turned on the TV, and it will do everything mentioned in the symptoms but all within 1 second. I've checked the voltage on the 24v rails and 5vsb and all read 0v. My reference on the cold side was a chassis ground.

[Naturallyk2]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

I also checked the capacitance of the main filter cap which is rated at 390uf, it currently reads 380uf so it looks like it's fine.

[realdealthill]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

Do you have an image on the scree (flash light test)??

[Naturallyk2]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

No. The TV turns on briefly then just dies out. Nothing comes on the screen. I just noticed that the Vizio standy light fades out instead of abruptly shutting off. That kind of hints at a short somewhere or ground out. The when you press the power button, the TV will not turn on. You can't even hear the caps.

[budm]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

So both fuses on the main boards are good?
We need dcv reading of each pin of the connector of the power supply board that goes to the main board when TV is plugged into outlet but not turned on, and when the power switch is activated.
You MUST pin down the pin name and follow by the dcv reading of each pin so we can see what are missing.

[Naturallyk2]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

Both fuses on the main board are good.

All pins on mainboard from PS read 0v across the board with power plugged in. When pressing the power button, all pins read 0v still.

[budm]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

So in the beginning the standby power supply was working and now it is dead, so disconnect the cable between the power supply and the main board to see if you will get the STBY Voltage back.
We also need clear straight shot pictures of the whole power supply board top and the bottom side.

[Naturallyk2]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

After disconnecting main board from PS, the voltages still read 0v on Standby. Here are the pictures as requested. Do you want me to remove the aluminum cover from the PS for better viewing?

[Naturallyk2]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

I noticed something in the photos I've uploaded. The the thermistor (NTC1) Large green looked cracked from its plastic covering. I removed it from the power board and found the resistance at room temperature to be 4 ohms. Any thoughts on this?

[Naturallyk2]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

The printing on the thermistor reads as follows: SCK 0512 746

[Naturallyk2]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

So in the beginning the standby power supply was working and now it is dead, so disconnect the cable between the power supply and the main board to see if you will get the STBY Voltage back.
We also need clear straight shot pictures of the whole power supply board top and the bottom side.

Just a heads up Budm, I've pulled the two main film caps and tested them. Both have met the 22uf capacitance requirements. You had helped me with an issue like this over 1.5 years ago on another TV and I went straight to the Film caps this time only to find that they were good. I guess we'll see what the real problem is with this TV since it seems to be a rare issue.

[dick_barton]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

The printing on the thermistor reads as follows: SCK 0512 746

It's a 5 ohm, 12 Amp device.

[vinceroger69]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

Try heating the whole power supply up with a hair dryer for a few minutes i wonder if it has high esr capacitors maybe the 5v standby one.

[Naturallyk2]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

It's a 5 ohm, 12 Amp device.

Reads 5ohms off the board. Shot in the dark without a schematic. I removed the main filter cap and it reads at 387 uF (390uF cap). I checked the MOSFET underneath the board and the MOSFET works like it should. What on earth would cause this unit to just fast drain out power after 3 seconds? I re-examined the board and saw something a little off. I've seen a few people with this same model that had burned out coils. This board doesn't have it, but there is slight discoloration in the traces around the area.

[dick_barton]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

I also checked the capacitance of the main filter cap which is rated at 390uf, it currently reads 380uf so it looks like it's fine.

Can you measure the DC voltage across the two pins of this capacitor.

[dick_barton]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

There's a Youtube video
https://www.youtube.com/watch?v=jR2UZhoDC2c

[Naturallyk2]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

Can you measure the DC voltage across the two pins of this capacitor.

Mounted on the TV, no. Is it ok to have the board off of the TV on the ground to test it that way?

[budm]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

Btw, are you sure about the STBY pin and the 5Vstby pin? One is the same as PSON, and another is the 5V standby.
Can you give me the pin name of the power supply connector that goes to the main board?

[budm]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

Btw, I cannot read the P/N of the power supply board to get better pictures from shop jimmy.

[Naturallyk2]

Re: Vizio VO47L-FHDTV10A turns on and then off (3 seconds)

Btw, are you sure about the STBY pin and the 5Vstby pin? One is the same as PSON, and another is the 5V standby.
Can you give me the pin name of the power supply connector that goes to the main board?

Holy smokes just made a breakthrough. I guess redoing the soldering work on the ceramic cap on the main filter cap on the PS has now given me the ability to at least turn the TV on. The main cap reads 168 VDC off and 391 VDC on. Problem is, I can't turn the TV off once I press the power button. The backlights or picture does not come on on the TV either.

BUDM, the P/N to the PS is DPS-433bp rev C . Will get you the reading off the main board now that I can actually turn the TV on.