Vizio M502i-B1 won't turn on

[Misterfixit]

I have a Vizio model M502I-B1 which doesn't turn on. No led back kites, no sound, nothing. I have tried power cycling and checked all Vizio related you tube videos but nothing seems to have tacked this issue. Overall, this set has 4 circuit boards as follows: power supply, led driver, main board and t-conn board. I have noticed a small(tiny) led that lights up on the main circuit board. At this point, I am trying to identify which board is bad.

I have taken voltages on the power supply board (715G6100-P03-003-002h) at the two connectors.
CN9101
Suppose to be. Measured
5 volts. 5.11 volts
12 volts. 11.58 volts
12 volts. 11.58 v
24 volts. 19.58 volts

CN9102
Suppose to be. Measured
12 volts. 11.58 volts
24 volts. 19.58. Volts

In this particular set, I do not see any markings on the power supply board near the cables that say standby power. I am assuming that the power supply board is energized all the time. I am of the opinion that something is dragging the 12 volt and 24 volt voltages down and perhaps the power supply board is ok. I would appreciate any assistance that can assist me in my trouble shooting.

[Misterfixit]

Re: Vizio M502i-B1 won't turn on

Here is a picture of the power supply board

[Misterfixit]

Re: Vizio M502i-B1 won't turn on

Here is a picture of the back of the set showing all of the circuit boards.

[dskall]

Re: Vizio M502i-B1 won't turn on

12v seems okay. Don't know how this tv works. If you unplug connector to led board does 24v come up? What is voltage across main caps?

[dick_barton]

Re: Vizio M502i-B1 won't turn on

Can you post a photo showing the legends and connector clearly.

[Misterfixit]

Re: Vizio M502i-B1 won't turn on

Thanks for replying. When I disconnect the top power supply connector (Cn9102) to the led driver board, the voltages at the power supply do not change at all. I have attached a closeup picture of the two connectors. One of the connectors (Cn9101) goes from the power supply board to the main circuit board. The other connector (CN9102)goes from the top of the power supply board to the led driver board. This is the connector in which I temporary removed to check voltages(which had no effect).
Incidentally, there is a cable that runs between the Led driver board to the main circuit board that I didn't do anything with.

[Misterfixit]

Re: Vizio M502i-B1 won't turn on

Here is a picture of the other connector located towards the top of the tv (CN9102) which goes to the led driver board. I will next try and measure some voltages on the power supply caps

[Misterfixit]

Re: Vizio M502i-B1 won't turn on

Also, there are two main capacitors on the power supply board. I measured 393 volts on each of them separately. These caps have a 450 volt dc rating on both of them. No bulges on any of the capacitors in the power supply board that I can observe. Let me know what else I can do

[dick_barton]

Re: Vizio M502i-B1 won't turn on

The focus is poor and hard to read. The 393V across the capacitor I think would be correct or at least close to the value expected.

With the mainboard connected, what voltage do you have on PS_ON and ON/OFF with the set in standby and then when you try to switch it out of standby

[budm]

Re: Vizio M502i-B1 won't turn on

Pput meter probe on the two legs of C820 then turn on the TV and watch and see how high the Voltage goes up to and how low it drops down to after 5 seconds, turn off the TV and then move the probes to the two legs of C821 and repeat the same test. You must keep the probes on the cap BEFORE TURNING ON THE TV.
Vizio LNTVEV24XUAA8 LED Driver
http://www.shopjimmy.com/vizio-lntve...led-driver.htm

Vizio ADTVD3613XA7 Power Supply
Pictures provided by shopjimmy

[Misterfixit]

Re: Vizio M502i-B1 won't turn on

On c820, the voltage rises to 19.41 and falls to 17.7 volts after 5 seconds
On c821, the voltage rises to 19.41 and falls to 17.8 volts after 5 seconds

[Misterfixit]

Re: Vizio M502i-B1 won't turn on

Reply to Dick Barton: the remote control doesn't seem to have any affect when the remote power button is pressed. So when I plug in the power, I measure 3.23 volts on the ps_on and 3.31 volts on the dim on/off connections on power supply board connector CN9101. When I attempt to switch the remote power button on, the voltages are unchanged. Incidentally, on the legend of this connector, it has a N/C in the column next to PS_on. I am assuming that this means that it is not connected.

[dick_barton]

Re: Vizio M502i-B1 won't turn on

There are two parallel sets of pins (9 x 2) so 18 pins in total. The NC and the PS_On are two separate pins. The Dim ON/OFF again are two separate pins. One pin is Dim and the second pin is ON/OFF
The legend alongside shows the pin layout of the connector.

[Misterfixit]

Re: Vizio M502i-B1 won't turn on

Reply to Dick Barton: sir, you are correct in your observation of the connector. There, indeed, is two sets of 8 pin (not 2 X 9) connections. I was able to measure the "on/off" pin of connector cn9101, it measured 1.14 volts. The remote control power button has no effect on this voltage. Please advise what else I can check

[budm]

Re: Vizio M502i-B1 won't turn on

FYI: as you can see the connector of the power supply that goes to the LED driver board only has red wires for the +24V, and Black wire for the GND return to feed the LED driver board with 24V, the ON/OFF PIN, DIM PIN are not used and now wires attached, see picture: https://www.badcaps.net/forum/attach...0&d=1493318280
The connector on the right side of the driver board that goes to the main board contain the BL-ON and dim control signals, but the connector on the LED driver board does not show the pin function. Right now you are not getting the Boost Voltage so it may mean that the LED driver board is bad or it is not getting the BL-ON from the main board.

[Misterfixit]

Re: Vizio M502i-B1 won't turn on

Thanks budm: I have a couple of questions as follows: 1. Is the boast voltage derived on the led driver board? 2. I measured the voltage capacitors c820 and c821. The capacitor values and voltage rating cannot be seen unless I pull the caps off of the board to view the underside. What is voltage suppose to be on the capacitors c820 and c821? I measured only 19 volts. Is it suppose to be higher? Is this the boast voltage that you referred to?

I assume that the led driver board contains a switch mode power supply that derives the boast voltage. What do you propose should be my next steps? Still something is dragging down my 24 volt supply voltage.thanks for all your help.

[budm]

Re: Vizio M502i-B1 won't turn on

"1. Is the boast voltage derived on the led driver board?" Yes, the yellow inductor is part of the boost converter circuit.
"2. I measured the voltage capacitors c820 and c821. The capacitor values and voltage rating cannot be seen unless I pull the caps off of the board to view the underside. What is voltage suppose to be on the capacitors c820 and c821? I measured only 19 volts. Is it suppose to be higher?" When the booster circuit is not turned on you will only see the feeding Voltage, in this case it is the 19V, those two should be rated at over 100VDC when it is running, the Voltage depends on how many LEDs there are in the LED string + Vdrops on the PWM controlled MOSFET and the current sensing resistor. Right now we do no know if the driver board is getting the BL-ON signal to turn on the boost converter circuit and the LED driver circuit or not, that is problem we need to find out.
You can spend $15 dollars on the driver board to find out if it is the board or something else.
http://www.shopjimmy.com/vizio-lntve...led-driver.htm
BTW, lately in the Vizio TVs we have found that what the Voltage printing the board does not really match what it is putting out.

[Misterfixit]

Re: Vizio M502i-B1 won't turn on

One other thing that is on my mind: the remote control doesn't seem to have any effect on the set when I push the power button on. I assume that the IR sensor is located on the lower right side of the set. I have replaced the batteries on the remote control and try to point it at the sensor while the tv is overhanging the table in which I am working on. (Set is screen facing down, but overhanging table so remote control hopefully will send signal to IR sensor). I have seen a You-tube video where a faulty IR sensor caused the set from turning on. The tech. Unplugged the IR sensor which caused the set to turn on. I also temporarily unplugged IR sensor cable and nothing happened. Is there something I can measure to assure that the remote control operation is working. When the remote control is operated, I don't even hear a click (from a relay) or anything went it is operated. Also, the TV set power button doesn't seem to function either. To engerize and shut off the set, I been plugging in the power cord. One other observation I noticed is, when the set is plugged in, there is a tiny led light that is on (it shines) located on the main circuit board

[dskall]

Re: Vizio M502i-B1 won't turn on

You have a connector from your buttons, ir sensor etc. to mainboard. One or more pins should change voltage when you press buttons. Usually several pins will have around 3.3v check with voltmeter

[Misterfixit]

Re: Vizio M502i-B1 won't turn on

On the IR sensor board, I have a connector that gas five wires. First wire(black) is 3.3 volts , second wire (black) is 0 volts, third wire (green) is 0 volts, fourth wire (white) is 0 volts and fifth wire (red) has 5.1 volts. Nothing changes (voltages stay the same) when I press the remote control on button. I am measuring these pins one at a time with the ground on the power supply ground connection at connector cn9101. Is there somewhere else I should be connecting my volt ohm meter Ground to or across to verify the if sensor board works?