Vizio VA320E amber light won't go white

[jakeklem]

Hello all,
I'm having trouble tracking down the problem with this set. As stated in the title, I can't get it past an amber light.

Power board has 5v standby, but nothing happens when power switch is pressed. I measured the voltage running to the power switch from the main board. The yellow wire in the power switch connector picture reads ~230mv and drops to ~50mv when I hold the button in.

When I jump 3v to PS_ON, I get: 24v and 12v on the power board.
I noticed there is a regulator at u708 that has 5v coming in and about 230mv going out. Seems to be the problem, but can't find the part number. ADI911 is marked on the top.

Thanks for any help!

[newtothis]

Re: Vizio VA320E amber light won't go white

Could do with better images, Can you get us a closer picture of the connector on the PSU that goes to main so we can read the voltage legend.

[jakeklem]

Re: Vizio VA320E amber light won't go white

Sure thing. Lets see if this is big enough to read.

[budm]

Re: Vizio VA320E amber light won't go white

Can we see good close up of U708 so I see if it is fixed or adjustable or it is something else?

[jakeklem]

Re: Vizio VA320E amber light won't go white

This would be adjustable, right? Sorry for the blurry pic, it's as good as my phone can do. If need be I can use a microscope to get a better one.

Also, wanted to say thank you Budm, as I've seen some of your posts around the net and they really helped me get started in doing LCD repairs.

[budm]

Re: Vizio VA320E amber light won't go white

Hmm, Looking at the picture with the tab to the left, is that positive leg of small electrolytics cap connected to the big tab?
Is the bottom pin connected to ground (negative leg of that same electrolytic cap)?
If it is regulator, it will be a fixed regulator because it does not have resistor network connected to the bottom pin.
Also check the resistance between tab and GND to see if it also show low resistance.

[jakeklem]

Re: Vizio VA320E amber light won't go white

Yes, the tab is connected to + of the cap.
Bottom pin doesn't look like it's directly connected to negative leg, but it's hard to me to tell if it's in the same circuit with other components in between. I can provide a close up there if that would help.
Resistance between Tab and all pins show ~ 8.75 Mohms and slowly began to drop while reading.

[budm]

Re: Vizio VA320E amber light won't go white

I need Tab and GND (which should be the negative leg of that cap), what I am trying to find out if the output tab is being loaded down by very low resistance or not.

[jakeklem]

Re: Vizio VA320E amber light won't go white

Oh I see. Looks like 400 ohms from tab to gnd on the cap.

[budm]

Re: Vizio VA320E amber light won't go white

OK, the resistance is not low enough to cause problem.
So we need to find out what the Voltage output of this IC should be.
I have no luck finding anything by those numbers.

[jakeklem]

Re: Vizio VA320E amber light won't go white

I haven't been able to find it either. Am I hosed or is there another way?

[jakeklem]

Re: Vizio VA320E amber light won't go white

Did a little more poking around tonight and found another regulator that seems odd. Markings on it are 7LD 1122.

Readings with PS_ON jumped 3v
in: .5v
out: .4mv
tab: .4mv

Datasheet
Any thoughts?

[budm]

Re: Vizio VA320E amber light won't go white

0.5V in put is way too low for it to work, the minimum output Voltage for these LDO regulator is about 1.20V so the input has to be at least 2.5V for it to work.

[jakeklem]

Re: Vizio VA320E amber light won't go white

After messing with this thing a little more, I found that the output voltage for the first regulator at U708 had a 3.2v output. I'm not sure what I did to make it show that voltage, but it only happened in one instance of plugging in/ unplugging the set.

Is it possible this regulator is still good? Could something else be causing the fault?

[budm]

Re: Vizio VA320E amber light won't go white

It is going to be tough without the diagram to find out what circuit feeds the input Voltage to this regulator. It can be bad connections, etc.

[jakeklem]

Re: Vizio VA320E amber light won't go white

Oh I forgot to mention. I bought a main board off ebay that is supposed to be in working order. However, I get the same results with it. I suppose there is a chance that both boards have exactly the same problem, but is there something else I could look at on another board?

[budm]

Re: Vizio VA320E amber light won't go white

In post 1 "The yellow wire in the power switch connector picture reads ~230mv and drops to ~50mv when I hold the button in."
What do you get on the pin of the main board if the switch assembly is not connected?

[jakeklem]

Re: Vizio VA320E amber light won't go white

AHa! You're on to something bud. With the connector off, the pin reads 3.2v. The regulator in question also measured 3.2v. So is this a shorted switch or the circuit board the switch is attached to?

[budm]

Re: Vizio VA320E amber light won't go white

Can you show the pictures of this board? Is it switch assembly and IR combo?

[jakeklem]

Re: Vizio VA320E amber light won't go white

See attached. It's just the switch assembly. IR is separate.

Do you want a close up of any portion of the board?