Vizio sv421xvt

[budm]

Re: Vizio sv421xvt

"Q2 Off 0v On 2.713V" Do you mean Q5?

"Can you tell me againg the DC voltage on the Collector of Q1 and Q5 when the TV is off and when the TV is on?"

[landyboy]

Re: Vizio sv421xvt

Sorry yes Q5

[budm]

Re: Vizio sv421xvt

OK, we can try using the signal at the Collector of Q5 as the PS_ON. You will have to remove that wire on pin1 (PS_ON) from the connector, then solder on 470 Ohms (330 Ohms, 500 Ohms will be fine, or may be 1K) to the that wire, the other end of the resistor will be soldered to the Collector of Q5. Hopefully, Q5 will provide enough current to bias on the transistor on the power supply board enough to turn on the power supply.

[landyboy]

Re: Vizio sv421xvt

Ok I did that and now the set powers on like normal. But.... I do not have any HDMI ports it says no signal on all inputs it also appears that the optical out has no power (lack of light in port)

[budm]

Re: Vizio sv421xvt

But if you force on by connecting the resistor between PS_ON wire and the 5VSTBY, all the function works? We already know that the main board has problem with the PS_ON signal, we do not know if anything else is broken on the main board.

[landyboy]

Re: Vizio sv421xvt

Yes all functions work I can access menu and navigate.

[budm]

Re: Vizio sv421xvt

In that case, we need to find some other spot for toggling the HI/LO signal for PS_ON, may be the 470 Ohms on the Collector is too much load on Q5.

[landyboy]

Re: Vizio sv421xvt

OK I did use a 680ohm resistor it was the closest to 470 i could find.

[budm]

Re: Vizio sv421xvt

Try going higher. Right now we are not sure what the function of Q5 is, you should also monitor if the Collector voltage of Q5 is still able to swing high to 2.7V.

[landyboy]

Re: Vizio sv421xvt

Well this set has a mind of its own. After removing the re-feed to the standby pin and putting it back to normal the set now turns on. Although I still have no HDMI imput.

[budm]

Re: Vizio sv421xvt

Hmmm. Now it is good time to see what voltage of the PS_ON is and also check the Q1, Q2, Q5, Q7 when it is can be turn on.

[landyboy]

Re: Vizio sv421xvt

With set powered on
Q1 0
Q2 .686
Q7 .124
Q5 2.796
Standby Pin 2.753

[budm]

Re: Vizio sv421xvt

It looks like Q5 is the one, I wonder if there is bad connection from Collector of Q5 to the PS_ON resistor R11, R1 (R11 is in series with R1). All we did was soldering the resistor to the Collector of Q5.

[landyboy]

Re: Vizio sv421xvt

Yea thats what I'm thinking. I now have to try to figure out why I don't have HDMI inputs. Maybe firmware?

[budm]

Re: Vizio sv421xvt

I do not know about the HDMI, if you find out if it has firmware up date for this model, you can try. Otherwise it works OK on cable, Component inputs, etc?