Vizio SV470M Standby, no power on, troubleshooting trouble

[redheaddiesel]

I picked this TV up from a friend after fixing a panasonic plasma. I have basic electrical troubleshooting skills, and am a teacher who is really good at following directions. Other than that, I'm a Newbie in terms of TV troubleshooting.

Basic symptom is that when plugged in, the Vizio icon lights up, but nothing happens at all when you try to turn the power on. Previous owners said they were watching and it just died.

From what I've been told, the problem is either the main board or the power board. I'm wondering about the procedure to tell which. That alone would be a big help, but if it was also possible to tell what on the board was bad, then I might even be able to fix it and save $100 for the main or $60 for the power board. I did some poking with my multimeter, and here is the data I have:

Vizio light is on, but nothing happens when the power button is pushed.

On the powerboard:
I have standby 5v from the three "ST/+5V" tabs on the powerboard to the main.
I have 12v at the three tabs on the same plug labeled "12v".
I have 2.4 v at the tab on the same plug called "on/off."
All the grounds on this plug are clean to ground.

The plug next to it with Dim, Inv Com, VBR_A, Status, AC Det, are all dead.

There is voltage from the main board to the standby light (of course) as well as 5v to the IR chip on the bottom corner of the TV.

I'm not sure if any of this helps, or if I'm even following the proper procedure.

If nothing else, to know which board to buy would be nice.
If I could figure out which component on the board was bad, and if it was replaceable, that would be even better.

Thanks in advance for any help for the Noob!

Matt.

[retiredcaps]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

On the powerboard:
I have standby 5v from the three "ST/+5V" tabs on the powerboard to the main.
I have 2.4 v at the tab on the same plug called "on/off."

While your TV may not have this problem, Vizios are notorious for bad voltage regulators. They are easy to test. See sig file below.

The main board is responsible for generating on/off. At 2.4V, it may not be enough to turn on the TV? On some TVs, it needs to be > 3V.

Also post clear picture as my sig file below.

[redheaddiesel]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

This article is REALLY helpful. I'm going to pick up a digital multimeter today and check those readings. That would be really great if were a regulator problem. Are these easily available and solder on and off like anything else?

Thanks again.

[redheaddiesel]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

Retired Caps,

I have some data to report. I think you're idea was for me to find the data sheets online, but I'm having some trouble with the 1117's. I'll post the data and if any one has a minute to look maybe it will mean something to them.

First, there are four 1117 regs.

Line one looks like "backwards C", 11gld or something like that. It is really hard to read.
Line two is simply "1117"

U7
"backwards C", 11gld
1117
2.05
3.30
5.15

U4
"backwards C", 11gld
1117
0
1.26
3.30

U2
"backwards C", 11gld
1117
2.06
3.31
5.16

U6
"backwards C", 11gld
1117
6.91
8.16
12.19

U3
L501
G1084
2.05
3.30
5.14

U5
L501
G1084
2.04
3.29
5.15

U9
L501
G1084
.55
1.80
3.29

U8
7805CT
RAD949G
12.18
.01
5.04

I think this is all of them.
The eight legged spider squares are not regs, neither are the two on one side and one on the other (like a tricycle) right?

Thanks!

Matt.

[redheaddiesel]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

Attached is a picture of another main board. My kids lost my camera charger. This is identical, though.

mm

[budm]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

Can I see the pictures of the whole back side of the TV so I can see how all the boards are connected. Also good pictures of the power supply board.

[redheaddiesel]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

Attached are the actual pics of the TV.

[redheaddiesel]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

One more pic that didn't make it.

mm

[tom66]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

Your regulators all look good.

There are some white fuses near the power connector on the main board, verify if these are good using an ohm meter.

[redheaddiesel]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

Thanks Tom! I'll check and post.

Matt.

[redheaddiesel]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

Tested the main fuse (like an automotive cylinder fuse), five grey axial fuses, and a strange dual cylinder on end (like a silo) with an orange bridge. All of these had continuity.

There is a used but working main board on ebay now for $45. Normally these go for around $100. If I knew the problem was the main board on this one I'd be tempted. Would you guys recommend a used board?

Finally, I keep going back to the 2.4v at the on/off tab (this is a wire between the main and power board). Seems like everything should be either 3.3, 5, 12, or 24 volts, right? Should this 2.74v send flags? If that voltage is off, would it prevent the TV from powering on?

If my thinking is right, is it ludicrous to think of jumping 5v to that tab and seeing if it would power on?

OK, venting aside, there is probably a systematic next step I should follow. Thanks again for all the help so far.

Matt.

[budm]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

Can I see closed up pictures of the white connectors (top left of the board) on the power supply/inverter board so I can see the label on the connector?

[redheaddiesel]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

Pics attached.

[redheaddiesel]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

Two others

[redheaddiesel]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

Not sure why it only uploaded one picture at a time.

[budm]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

OK, 2.4vdc for the ON/OFF of the 12v power supply control is OK otherwise you will not have the 12VDC output.
"The plug next to it with Dim, Inv Com, VBR_A, Status, AC Det, are all dead. "
the pin INV Com is actually is INV ON which is the receiving pin for the signal from the main board to turn on the backlights. So the main board is not sending the on signal for the backlights. To verify if the backlights circuit is OK or not, you will have to remove that INV ON cable from that pin (we do not want to back feed the signal from the resistor to the main board), then use 1K resistor connected between the 5VSTBY and the INV ON, that should turn on the backlights when you turn on the TV.
Also check the AC Detect signal pin when TV is off to see what you get.

[redheaddiesel]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

Bud,

Your message is very helpful and clear. The one part I don't understand, because of my own ignorance, is

"then use 1K resistor connected between the 5VSTBY and the INV ON"

Is this a setting on my multimeter that I run between them? A jumper wire? Once I know I can check tonight. I'll also look at the AC Detect.

Also, If the TV is plugged in, does nothing else but light up the Vizio icon orange. So, to test the AC Detect with the TV off, does that mean plugged in in standby mode as I'm describing? I think the only other option is to unplug it.

Thanks Bud!

Matt.

[budm]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

The 1K resistor will be connected between the 5VSTY PIN and the INV ON pin, you are basically feeding the output of the 5VSTBY to the INV ON pin through the 1K resistor to force the inverter to turn on.
As I noted in post 16: you will have to remove that INV ON cable from that pin (we do not want to back feed the signal from the resistor to the main board).

The AC DET pin, check the DC voltage with the TV is plugged in but in the off setting, take the reading, then hit the power switch and take the reading (black probe of the meter to the chassis, red probe on the AC DET pin.

[redheaddiesel]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

One thing to add just in case it is significant. Even in standby mode (which it doesn't come out of) the heat sink on the microprocessor gets pretty warm. Is this normal?

[tom66]

Re: Vizio SV470M Standby, no power on, troubleshooting trouble

That sounds abnormal -- like it is locking up. It should normally be cool when in standby. It is supposed to use less than one watt in standby.