VF550M - orange logo only; power supply appears good

[jim92128]

Vizio VF550M 55" TV
Power Supply: 0500-0507-0740
Main board: 0171-2272-2964 or 3655-0062-0150(4C)

When plugged in, the Vizio logo on the front is illuminated orange. There is no response from the unit when the on button is pressed via the remote or the manual on/off button on the side of the unit is pressed. The Vizio logo does not glow white and there is no other response from the unit.

I first checked the power supply board:

It looks like there is a single fuse on the power supply board. I tested it with a multimeter (in circuit) and I measured 0.1 ohms. It looked like I might have to unsolder it from the board to test it out of circuit, and I did not want to remove the board from the chassis at this time. I placed a jumper across it and turned the TV on. The effect was the same. The Vizio logo was illuminated orange but the TV would not turn on either via the IR remote or the manual button on the side of the unit. I then removed the jumper.

The power supply board appears to be on as there are output voltages. It also appears that the PSON signal is active. I took some measurements with a multimeter:

CN5 connector: measured 5V standby, 12V, and the PSON measures 3.16V
CN4: measured 18V where indicated
CN3: measured 24V where indicated
CN2: measured 24V where indicated

The PSON voltage remains at 3.16V when I depress the manual on/off button on the side of the unit. It appears that the PSON signal is active and the board is on. I have read that PSON is active at approximately 3.2V.

I have seen a YouTube video which says that there is a secondary enable which goes from one of the inverter boards, to the power supply board, which tells the power supply to turn on fully. Is this correct? What pin is would I check on the Power Supply board for that signal and what would be the voltage?

I also checked the three small fuses on the main board. I checked them in-circuit. They all measured 0.1 ohms. I have not checked any LDOs.

I am wondering where to go from here. Suggestions? Thanks for any assistance. I will attempt to upload some photos of the unit with this post.

[jim92128]

Re: VF550M - orange logo only; power supply appears good

Hi all,

I just watched this YouTube video again. Since the power supply has the 24V signals active, I guess I am receiving the second enable, or feedback signal, from the inverter board to the power supply. This second signal is needed to turn on the 24V.

VIZIO VF550M Misdiagnosis and repair

https://www.youtube.com/watch?v=khSAoTAC3iM

[dskall]

Re: VF550M - orange logo only; power supply appears good

Do you have back lights? Might want to try reset. Go to factory reset listings on this site

[budm]

Re: VF550M - orange logo only; power supply appears good

You probably not getting the BL-ON to turn on inverter backlights circuit, right now the problem is on the min board because the logo does not turn white.
What did you check so far on the main board?
BTW, history of this TV?
There are lots of threads fir this model, bad eeprom?
https://www.badcaps.net/forum/search...archid=8066669

[jim92128]

Re: VF550M - orange logo only; power supply appears good

Thanks for the assistance so far folks. All suggestions are appreciated.

To respond to dskall, no, there are no backlights. The front Vizio logo remains orange. It never turns white as it normally would once the unit is fully turned "on".

It appears that this model TV must be on in order to perform a factory reset, since "Menu" and a numeric code must be entered.

[jim92128]

Re: VF550M - orange logo only; power supply appears good

To respond to budm,

Here is what I have tested on the main board:

I checked the fuses; F1, F2, and F3, in-circuit, with no power applied. Each read 0.1 ohms.

I then checked what look to be voltage regulators. I measured the voltages of each pin to chassis ground.

U8 (7805CT / RAD949G)
IN: 11.96V
GND: 0V
OUT: 5.04V

U3 (1084 / 0931gL)
GND: 2.06
VO: 3.31V
VI: 5.08V

U5 (1084 / 0931gL)
GND: 2.05
VO: 3.31V
VI: 5.08V

U9 (1084 / 0931gL)
GND: 0.55V
VO: 1.8V
VI: 3.30V

The values on U9 look somewhat suspicious.

Regarding the history of the TV, I am the original owner. The unit was purchased in 2010. Two years ago, the HDMI1 input ceased to function. I had the inputs assigned as follows:

HDMI1 : DirecTV
HDMI2 : Chromecast
HDMI3 : DVD Player
HDMI4 : open
HDMI5 : open

Once HDMI1 failed, I moved the DirecTV box to HDMI4. I have had no problems since this was done.

Friday night, I tried to watch a DVD and noticed there was no signal on HDMI2. I took the DVD player and cable and tested them with a second TV. They worked fine. I then tried plugging the DVD player into HDMI4, but there was no signal. This was very strange since the DirecTV box was using this input just minutes before, and it was working fine. I unplugged the DVD from HDMI4 and plugged in the DirecTV box again. I had a signal on HDMI4 as expected. Each time I unplugged/plugged a source in, I would power down the TV and source, unplug/plug the source unit in, and power on the TV and source.

I then plugged the DVD player into HDMI2 once again, but this time the TV was on, as was the DVD player. Once I did this, the TV shut off, and it's never been on again. I guess the "hot swap" I did with the DVD player and TV both being turned on was not a good thing. As I noted though, there were some strange things going on with the TV prior anyway.

[ecking767]

Re: VF550M - orange logo only; power supply appears good

you didn't measure u2 and u6. u6 shouldn't be active in standby mode

[jim92128]

Re: Vizio VF550M - orange logo only; power supply appears good

It appears I missed some of the regulators on the main board. Here are the voltages measured with respect to chassis ground.

U2 (9ub / 1117)
ADJ : 2.06V
OUT : 3.31V
IN : 5.11V

U4 (9ub / 1117)
ADJ : 0V
OUT : 1.24V
IN : 3.31V

U6 (9ub / 1117)
ADJ : 6.85V
OUT : 8.09V
IN : 11.97V

U7 (9ub / 1117)
ADJ : 2.05V
OUT : 3.30V
IN : 5.08V

U45 (9ub / 1117)
ADJ : 2.06V
OUT : 3.31V
IN : 5.08V

[budm]

Re: VF550M - orange logo only; power supply appears good

Those Voltage readings are correct, the output Voltage of the adjustable regulator = 1.25Vref + Vadj
I.E.
U2 (9ub / 1117)
ADJ : 2.06V
OUT : 3.31V
IN : 5.11V

1.25Vref + 2.06V (Adj) = 3.31 Vout
I suspect something is going on in the HDMI section that is stopping the main board to function properly.

[ecking767]

Re: VF550M - orange logo only; power supply appears good

Those volt measure are good but, in standby mode all of the regulators shouldn't be active, U9 shouldn't be active.

so you could a bad eeprom or a CPU related problem

[jim92128]

Re: VF550M - orange logo only; power supply appears good

Thanks for the assistance guys. I think what I will do is keep my eye out for a main board on eBay with my exact part number (none listed right now), install it, and cross my fingers.