Vizio E421VA No picture

[rod30]

No standby light. When testing voltages I find that the power supply puts out a good 5v when the logic board is disconnected. When it's reconnected the voltage drops to 2.7v. Would somebody please send me in the right direction to determine what may causing the voltage drop. Thanks again for your help.

[dick_barton]

Re: Vizio E421VA No picture

What are the symbols alongside the top red connector, from left to right?

[rod30]

Re: Vizio E421VA No picture

See photo

[dick_barton]

Re: Vizio E421VA No picture

Disconnect the power supply from the main board and power up. Hopefully the +5V will come up as you indicate in your initial post. If it does and while still disconnected from the main board use a 1K resistor from +5V to PS ON and then measure the 12, 24V supplies.

[rod30]

Re: Vizio E421VA No picture

Well, that's interesting. When I ran 5v to PS-ON the 12v & 24v terminals showed 2v and 4v volts.

[dick_barton]

Re: Vizio E421VA No picture

What voltage is on PS On before you connect +5V to it?

[rod30]

Re: Vizio E421VA No picture

The PS-ON has no voltage. Only the two 5v show anything. OK, I think I did it incorrectly. 5v to PS-On now gives me 12v and 24v.

[dick_barton]

Re: Vizio E421VA No picture

I did mean the PS_ON Pin. So it's 0v before you connect the 5V with 1K resistor which is fine. Try a 470 Ohm resistor or there about and see if that makes any difference.

When disconnected as described above if neither the 12V & 24V come up then you appear to have a power supply fault.

[rod30]

Re: Vizio E421VA No picture

As you can see, I changed the other reply. I did get both 12 and 24 volts when I put 5v to the PS-ON.

[dick_barton]

Re: Vizio E421VA No picture

Look on the main board for IC regulators. The chances are that one of them has failed. Perhaps you could post a sharp image of the main board so we can see the components.

[rod30]

Re: Vizio E421VA No picture

Let me know it this is OK. If not I will do it again.

[dick_barton]

Re: Vizio E421VA No picture

What's the number on top starting 715G-xxxxx
Any of the 3 pin devices marked as Uxx

[rod30]

Re: Vizio E421VA No picture

715g3715-m01-000-004k

[dick_barton]

Re: Vizio E421VA No picture

I cannot make out the components on the picture but can see what appears to be two of the larger regulators as marked on the photo. There may be some 1117 regulators or similar which are also on the board that would need to be checked. Any capacitors with swollen top caps?

[rod30]

Re: Vizio E421VA No picture

The caps appear to be OK. In the past I have found a few that look good but were not. My next step was going to be to remove and test them. I have never attempted to replace an IC regulator.

[Diah]

Re: Vizio E421VA No picture

diagnose by dick_barton correct ... to be more sure disconnect the load of the Regulator, plug out the socket which go from main board to IR board. and check for 3.3 V and check the 5V go down.

[dick_barton]

Re: Vizio E421VA No picture

There's something pulling down the 5V supply and it could be one of the regulators because it's not quite a short circuit. As Diah suggests they probably obtain the 3.3V from the 5V via one of the regulators.

[rod30]

Re: Vizio E421VA No picture

I have remove all the cables from the main board and the voltage is still at 2.7v. Something on the main board is pulling down the voltage. At this point I will try to find a replacement board. I appreciate your time and effort going thru this with me. Sometimes they show up on Ebay and shopjimmy does have them. Do you know of other places I get a used one?
Thank you again.

[dick_barton]

Re: Vizio E421VA No picture

Shopjimmy does appear to have the market in the US. I buy locally within the UK.
Good luck