Vizio E470VA - No power

[Duemin]

Greetings. I have the above mentioned TV that shows zero signs of life.

Here is what i have found so far:
Upon plugging it in the front Vizio logo glows white for approx 1 second.
I checked the psu for the +5v standby and nothing. No voltages on any pins going to the mainboard.
If i unplug the mainboard, +5v Standby is indeed there. Plug in the main and the logo lights up, +5v goes away, no relay clicks, Nothing. Just dead.

Would this be considered a faulty main? I really cant afford to replace the entire board so I am looking for any insights on if / how this is repairable.
Thanks!

[budm]

Re: Vizio E470VA - No power

For you to have Vizio logo glow white it means the 5VSTBY must have been present, so leave the meter probes connected to the 5VSTBY pin and the chassis GND and then plug the TV into the AC outlet while keeping an eye on the meter to see if the 5VSTBy goes up to 5V and then drops down or not.

[Duemin]

Re: Vizio E470VA - No power

Thanks for the reply budm,
yes, 5v is present for only a second when connecting ac to the tv. if i leave the main board disconnected from the power supply the 5v standby stays on indefinitely. as soon as i connect the main it folds to 0vdc

[budm]

Re: Vizio E470VA - No power

OK, no power to the TV and have the boards all hooked back up then check the resistance between chassis GND and the 5VSTBY pin to see what kind of resistance you will get.
Can we also see the pictures of the whole backside of the TV so we can see all the board.
You can also try disconnecting all other boards that are connected to the main board and see if the 5VSTBY will be OK or not.

[Duemin]

Re: Vizio E470VA - No power

With everything connected as it should be. The 2 5v lines to ground measure to about 2.6k each.
With everything disconnected from the main it still behaves the same way.

Watching the +5v upon plugging in the set. It goes to 5.05v , 3.60v back to 5.05 then nothing. All within 1 second or so.

[budm]

Re: Vizio E470VA - No power

That unstable STBY can be due bad startup/running caps in the primary side of the circuit. I would check or replace those two small electrolytics caps close to that 7-pin SMPS IC for the standby power supply and see if it will become stable or not.
https://www.badcaps.net/forum/attach...7&d=1518027238

[Duemin]

Re: Vizio E470VA - No power

I will try that shortly. Thanks. It does stay stable as long as there is no load on it from the mainboard. I assume you mean the IC just above the white sticker on the right side of board?

[budm]

Re: Vizio E470VA - No power

I will try that shortly. Thanks. It does stay stable as long as there is no load on it from the mainboard. I assume you mean the IC just above the white sticker on the right side of board?

Yes, that is the STBY SMPS IC.

[Duemin]

Re: Vizio E470VA - No power

I replaced both caps in that area. No change. Same symptoms. =(

[budm]

Re: Vizio E470VA - No power

Then we need to test the 5VSTBY power supply by itself with 10 Ohms 5W resistor first to simulate 0.5A load and see if it can handle that much current or not.
What are the value of those two caps anyway?

[Duemin]

Re: Vizio E470VA - No power

They were 10uf 50v and 100uf 50v. I can make up a 10 ohm 5w real fast. Do i just shunt the 2 5v lines to ground and measure voltage?

[budm]

Re: Vizio E470VA - No power

Just on one of the 5VSTBY pin and GND.

[Duemin]

Re: Vizio E470VA - No power

13 ohms to ground it folds to 1vdc

[budm]

Re: Vizio E470VA - No power

OK, good at least we know it is not the main board that causes the power supply problem.
So for sure the caps and the rectifier on the cold side for this STBY power supply are good?

[Duemin]

Re: Vizio E470VA - No power

Not sure on rectifier. I can check the diodes this afternoon and let you know. Could it be the 5v regulator? (if there is one, i don't know my way around tv power supplies very well)
I see several near the main connector

[budm]

Re: Vizio E470VA - No power

It is just a simple regulated switching power supply that supplies the 5VSTBY Voltage, and also the switched Voltage to run other SMPS IC and the PFC IC.