VIZIO SV470M orange to white logo, Version 2

[lbairn]

This is my first post, so please let me know if I don't follow protocol.

I friend was going to trash this TV, so I decided to try to get it going again. Others on your site have posted a similar problem, so I just called this "Version 2".

When AC power is applied, the Vizio logo is orange, but there's no response to pressing ON/OFF. On the power supply board, there's +5 present but no +12 at the connector to the processor board. I disconnected the power cable to the processor board and used 1K resistors to apply +5 volts to DIM, INV_ON, and ON_OFF. (I did not apply +5 to ACDET.) The result was that now there's +12, the backlight comes on, and the logo turns white. I left the jumpers in place and reconnected the cable to the processor board. I measured voltages at the regulators and the results were the same as others have reported:
U9
556mV
1.8V
3.29V

U5
2.04V
3.2V
5.07V

U3
2.04V
3.29V
5.03V

U7
2.03V
3.28V
5.07V

U6
6.96V
8.21V
12.13V

U2
2.05V
3.29V
5.10V

U4
1.46mV
1.25V
3.29V

I've applied an audio signal at the inputs below the computer RGB connector and cycled through the inputs by holding down the INPUT button for three seconds each time, but I get no audio. I press the MENU button, but I get no video.

Also, with the +5 jumpers in place and the power applied to the processor board, the Power Supply board has several components that are way too hot. Q707 and C701 are running above 140F; C608 and FB601 are above 130F.
Here are my questions:
1. Does the basic problem seem to be the Processor board?
2. Are those caps, JFETS, and regulator on the Power board running way too hot, and if so, would you replace the caps first to see if that problem is resolved. I've posted pictures of the caps, but I need help figuring out the value of the box-shaped one (C701, sitting in front of Q707).

[CapLeaker]

Re: VIZIO SV470M orange to white logo, Version 2

PSon and BLon are generated on the main board. So if your main board is not sending PSon, the PSU won't turn on. You can try reflowing the main CPU, or try a new main board.
Maybe the main board is drawing too much current and that's why the PSU gets hot. I would concentrate on the main board first, as the PSU is responding to you forcing it on and all voltage rails are up and running.

[budm]

Re: VIZIO SV470M orange to white logo, Version 2

What did you use to check the temperature?
FB601 is the Ferrite bead inductor and has very low DCR so for it to get hot lots of current must be flowing.
You have main board problem.
https://www.badcaps.net/forum/attach...6&d=1487101359
Those 4 MOSFETs (Q707 is one of them) and C701 look to be for the backlights inverter circuit which should not on unless you are getting BL-ON.
There are stuff that need verification such as the DCV at the connector of the power supply that goes to the main board.
Q707 on the power supply board will still get hot if the cable between the power supply and the main board not connected, etc?

[lbairn]

Re: VIZIO SV470M orange to white logo, Version 2

Good points...thanks.

I'm using an infrared food thermometer.

Under no load (no back lights, no processor board), all PS components are at the same temperature (about 80F).

With only the backlight as a load, Q706 and FB402 are at 130F. All other components are below 120F.

With backlights and processor board as the load, Q701 and C701 heat to over 140F. C608 and FB601 heat to over 130F.

I'll concentrate on the main processor board first.

Thanks again, guys.