Vizio M502i-B1 Issues

[roundbox52]

My Vizio M502i-B1 (serial #LTYWRLAQ...) failed to turn completely on yesterday. Pressing power on the remote made the white light appear briefly however nothing showed on the tv. The tv was then unresponsive to the remote or the power button on the back side.

If I plug the tv in the white light now stays on. There is no screen image or backlight.

Some previous history:
I did have the main board replaced under warranty in 2015.
The sound stopped working 6 months ago so I rigged the tv speakers directly to an external receiver (wasn't a problem with the speakers themselves)

I only have a multimeter to check things with and I am not an electrical engineer although I would love to be. Hoping we can diagnose this together, but please take it easy on me as I don't know much, but will try my hardest .

FYI my mutlimeter is a Craftsman 82351, not sure how effective it will be for all the diagnostics I need.

Thanks!

[dick_barton]

Re: Vizio M502i-B1 Issues

Can you provide the voltages at the two connectors alongside the pin number, name, and voltage on each, for example.

Pin number, Pin, Name, Pin voltage
Pin 1, 12V, 11.9V
Pin 2, SW, 3.5V

[roundbox52]

Re: Vizio M502i-B1 Issues

I'm assuming I do this with power supplied to the tv and doesn't matter if I press the manual on/off button.

Connector cn9102
Pin #/Name/Pin Voltage
1/24v/20.04v
2/24v/20.04v
3/24v/20.04v
4/24v/20.04v
5/NC/runs to -400mv then starts over at 0 (no wire is connected to this terminal)
6/NC/runs to -400mv then starts over at 0 (no wire is connected to this terminal)
7/GND/-1.3mv
8/GND/-1.3mv
9/GND/-1.3mv
10/GND/-1.3mv
11/12v/11.67v (no wire is connected to this terminal)
12/OFF-ON/runs to -400mv then starts over at 0 (no wire is connected to this terminal)
13/DIM/4.37v (no wire is connected to this terminal)
14/NC/runs to -400mv then starts over at 0 (no wire is connected to this terminal)

Connector cn9101
Pin#/Name/Pin Voltage
15/5v/5.15v
13/12v/11.66v
11/12v/11.66v (no wire is connected to this terminal)
9/24v/20.04v
7/GND/-9.6mv
5/GND/-9.6mv
3/PS-ON/3.07v
1/DIM/4.4v

I cannot get to the right side of pins unless I take the connector out. Those readings are as follows:
16/5v/5.17v
14/12v/slowly drops to 0.3mv
12/12v/slowly drops to 0.3mv (no wire is connected to this terminal)
10/24v/4.8mv
8/GND/0
6/GND/0
4/NC/runs to +400 mv then starts over at 0 (no wire is connected to this terminal)
2/ON-OFF/runs to +400 mv then starts over at 0

[budm]

Re: Vizio M502i-B1 Issues

You need to press the power button On and Off to see if the PS-ON and the ON/OFF (BL-ON) will toggle High (>2.5V) and LOW (<1V) or not to know if the main board is active or not.
You can probe the connector pins at the wires entrance of the connector.

[roundbox52]

Re: Vizio M502i-B1 Issues

I originally thought my probes were too fat to not ruin the connector when probing from the entrance of the wire. I though wrong. Here are the corrected values for the right side of cn9101 in bold:

16/5v/5.17v
14/12v/11.66v
12/12v/slowly builds to 400mv then starts over at 0 (no wire is connected to this terminal)
10/24v/20.03v
8/GND/7.1mv
6/GND/7.1mv
4/NC/runs to +400 mv then starts over at 0 (no wire is connected to this terminal)
2/ON-OFF/1.342v

When pressing the power button On and Off I see no difference in the readings. #3/PS-ON stays at 3.07v and #2/ ON-OFF stays at 1.342v

[roundbox52]

Re: Vizio M502i-B1 Issues

Well looks like I'm just going to buy a new tv. Not sure what board is an issue so rather than guess and buy and guess again, I'd rather just put down another $200 and get a new tv, which will also have issues in a few years!

Isn't anything made with quality parts anymore?

[tvtimmy]

Re: Vizio M502i-B1 Issues

In a word.........no.
Find an older "bullitproof" tv and keep it running.

[roundbox52]

Re: Vizio M502i-B1 Issues

Interestingly when I plugged the tv in tonight I can see some led's are on, just the left top. I can't see anything on the tv though other than the lights. The power button still does not change voltages on the power supply board.

Any chance we think this can be narrowed down?

I took readings on the led driver board for the two connectors which work their way directly to the tv, I'm assuming these are for all the led's. For the connector for the left side of the tv I had (4) 30v readings and quite a few 11v readings however there were 4 or 5 that were only 3-6v. Perhaps these low readings are the led's that are on?

The right side connector had (4) 30v readings and all the others were 11v, I'm assuming they are all the same because none of the led's are on at that side.

Does this help any?

Is the main board not telling the power supply board to turn on?

Why are some of the led's on at the left side?

How can I diagnose this further?

Sorry for all the questions, just not ready to throw in the towel.

[roundbox52]

Re: Vizio M502i-B1 Issues

Well I ordered a main board and the initial issue seems to be fixed. I do however have a back light issue where I either have dark areas or bright areas. I've started a new thread about this specific issue.

Any help in diagnosing would be greatly appreciated.

https://www.badcaps.net/forum/showthread.php?p=767526#