Vizio xvt553sv not turning on

[chandan7]

My Vizio xvt553sv is not turning on. When it is plugged into the power the logo lights up with amber and then dims a bit after a few seconds. Pressing on the remote power button or the jog wheel button on the TV does not do anything. When it was working, the logo would start out amber and then go into blinking white and amber after a few seconds on plugging in power.

Not sure if this is a power board or main board issue. Any help will be very much appreciated. I check the output on CN201, CN202 and CN203 with the following results (the value in parentheses are the expected values as printed on the board):

CN201
1 0 (PWM)
2 0 (GND)
3 0 (GND)
4 5V (5V)
5 5V (5V)


CN202
1 5V (5V)
2 5V (5V)
3 5V (5V)
4 0 (GND)
5 0 (GND)
6 0 (GND)
7 0 (GND)
8 0 (12V)
9 0 (12V)
10 0 (12V)
11 0 (REMOTE_ON_OFF)
12 0 (BL_ON_OFF)
13 0 (NC)
14 0 (PWM)


CN203
1 0 (GND)
2 0 (GND)
3 0 (18V)
4 0 (18V)


I guess the 12V and 18V only turn on when REMOTE_ON_OFF is high, is that correct? I checked the voltage of pin 11 and 12 on CN202 with and without the power button pressed, but both times the reading was 0V on both pins.

I checked the voltage across 450v capacitors and all three read 292 VDC, not sure if that is correct. I can check again if needed.

I checked all the fuses on the power board (1), main board (3) and t-con (2) and none of them are open (~0 Ohm across them when unplugged).

I checked the bottom right regulator (U24) on the main board and all the pins read 0V. On the t-con the top right regulator (U6) is showing 2.2V, 3.3V and 5V for ADJ, OUT and IN and the bottom regulator (TU5) reads 0V an all the pin.

Happy to take more readings if that helps and I can take close up shots if you need specific ones.

Thanks in advance!

[budm]

Re: Vizio xvt553sv not turning on

The main board is not working, it is not sending PS_ON (REMOTE_ON_OFF), BL_ON (BL_ON_OFF), or Dimming (PWM) signals when power switch is activated.
Please locate all the 3-pin Voltage regulator ICs and report all the readings of all 3 pins and also provide the name as printed on the body of the ICs so we will know what they are.
Also try disconnecting the cable between the main board and the T-CON to see if it makes any difference.

"I checked the voltage across 450v capacitors and all three read 292 VDC" What is your AC line Voltage, 230V? If it is, then it should have about 325VDC (230 x 1.414) right at the two legs of the cap.

[chandan7]

Re: Vizio xvt553sv not turning on

Thank you for the quick response!

I could only locate 2 of the voltage regulators on the main board. Will take a closer look at it again when I get back home.

Regarding voltage, you are right the line voltage is 230V, will check the caps again later today.

[chandan7]

Re: Vizio xvt553sv not turning on

I could only locate 3 voltage regulators on the main board and t-con

U24 -> PCB designation
7805C02T -> line 1 of IC
RAN031G -> line 2 of IC
pin 1 = 0.00
pin 2 = 0.00
pin 3 = 0.00

TU5 -> PCB designation
M162 -> line 1 of IC
G1084 -> line 2 of IC
pin 1 = 0.00
pin 2 = 0.00
pin 3 = 0.00

U6 -> PCB designation
inverted C1100g -> line 1 of IC
1117 -> line 2 of IC
pin 1 = 2.06
pin 2 = 3.31
pin 3 = 5.10

I found a few more regulator looking things on the power board but I was not sure. I took some readings, but the readings were so high that I decided not to take any more since it might destroy my multimeter (which can only read up to 500 VDC). Here are the ones that I took

Q801A -> PCB designation
K3797 -> line 2 of IC
pin 1 = -110
pin 2 = 168
pin 3 = -110

Q801B -> PCB designation
K3797 -> line 2 of IC
pin 1 = -110
pin 2 = 168
pin 3 = -110

Q905 -> PCB designation
K3532 -> line 2 of IC
pin 1 = -110
pin 2 = 550
pin 3 = -110

I checked the voltage across the caps again and the reading is a steady 285 V. The mains read 210 VAC, so that may be the reason?

Removing the cable between main board and t-con does not help.

[budm]

Re: Vizio xvt553sv not turning on

U = IC
Q = Transistor

U24 is 5V regulator which will not be getting any input Voltage from the power supply until the man board sends out the PS_ON o turn on the main power supply.

U6 is correct.
U5 has no input Voltage so there will be no output.

[chandan7]

Re: Vizio xvt553sv not turning on

So main board is the problem? Is there some way to force it to send PS_ON?

I will see if I can find a replacement for the main board. Hope that is the problem . I already replaced it once a couple of years ago. Unfortunate that it keeps dying even with a voltage stabilizer.

[budm]

Re: Vizio xvt553sv not turning on

You can force on the power supply by connecting 100~500 Ohms resistor between the PS_ON pin on the power supply board and the 5VSTBY pin BUT YOU MUST disconnect the PS_ON wire that goes back to the main board otherwise you can damage the transistor on the main board.
To force the backlights on you will use another 100~500 Ohms between the BL_ON and 5VSTBY, YOU MUST disconnect the BL_ON wire going back to the main board also. You will force on the backlights AFTER FORCING ON the PS_ON pin.

[chandan7]

Re: Vizio xvt553sv not turning on

Thanks for the help Bud, but I guess even if I get the TV to turn on, it will probably not be very useful given that the mainboard thinks that it did not turn on the TV and hence I assume none of the HDMI or other inputs will work?

[Mrperezzzzz]

Re: Vizio xvt553sv not turning on

Were you able to replace the main board and successfully get the tv to work? 8 have the same model tv and the same issues I believe. The logo stay orange when plugged to power but does nothing more.

Thanks
Josh

[Nick's Tvs]

Re: Vizio xvt553sv not turning on

The failure on the main board is due to the BGA chip aka your CPU chip. The solder joints between the chip and the board have cracked/separated and will need to be fixed. Very time consuming and difficult unless you have the proper equipment. You can either remove the chip using both top and bottom heat and re-ball it with the help of a stencil or purchase a pre-balled chip. I really wouldn't suggest performing the repair unless you have done it many times in the past and are very familiar with your BGA rework station and all the heat profiles on your station.
Here is a link to our repair service for this board.

http://www.nickstvs.com/store/p1175/3655-0122-0150

feel free to contact us with any questions