Vizio E500i-B1 Backlight

[0S1R1S]

Re: Vizio E500i-B1 Backlight

Well, lightning can do odd things. A friend of mine is going to help me look at it tonight, he has a better meter that may give more accurate readings.
Is there anything else I can check in the meanwhile?

[CapLeaker]

Re: Vizio E500i-B1 Backlight

The 12V and the 24V is doubled up. Each transformer has one 12V and one 24V rail. Then they parallel the 2x 12V and the 2x 24V together. How about you are taking one diode on the 24V rail out let her run. See what gives. Then do the same thing with the other diode on that rail.

Something else: Unhook everything from the PSU and force the PSU on without the main board.
Take two 1k resistors and jump STBY 5V to PSon and the other resistor from STBY 5V to on/off. Plug the PSU in and it should be fully turned on.
If the 24V rail is up as it supposed to be, unplug the PSU, plug in the inverter board, then plug the PSU back in and see if the backlights are on.

[budm]

Re: Vizio E500i-B1 Backlight

The 12V and the 24V is doubled up. Each transformer has one 12V and one 24V rail. Then they parallel the 2x 12V and the 2x 24V together. How about you are taking one diode on the 24V rail out let her run. See what gives. Then do the same thing with the other diode on that rail.

Something else: Unhook everything from the PSU and force the PSU on without the main board.
Take two 1k resistors and jump STBY 5V to PSon and the other resistor from STBY 5V to on/off. Plug the PSU in and it should be fully turned on.
If the 24V rail is up as it supposed to be, unplug the PSU, plug in the inverter board, then plug the PSU back in and see if the backlights are on.

Something is amiss in that section, it is just simple rectification. I wish I have the board in front of me to do the test myself.

[CapLeaker]

Re: Vizio E500i-B1 Backlight

Something is amiss in that section, it is just simple rectification. I wish I have the board in front of me to do the test myself.

Yes, I know exactly how you feel. I wish too that I had some of these boards we try to help with, to have in front of me.

I did notice that the 24V also goes to the main board. Maybe it is loading it down?

[budm]

Re: Vizio E500i-B1 Backlight

That 24V goes to the LED Backlights booster circuit on the main board. I did tell him to disconnect that connector to see if the Voltage will go up to 24VDC again, but it did per his report.
It has two transformers that have the output after the rectifier connected in parallel, so it can not be that the 24V winding of both transformer are bad when the 12V is OK.

[CapLeaker]

Re: Vizio E500i-B1 Backlight

Sure about that? I can't find anything about the two 24V pins disconnected that go to the main board on CN9101.

[budm]

Re: Vizio E500i-B1 Backlight

I asked him in post 10~12, and he indicated the reading is still about 15V in post 11.

[0S1R1S]

Re: Vizio E500i-B1 Backlight

Yes, no matter what I do, the 24V on each connector is always reading at 15.5V.

[CapLeaker]

Re: Vizio E500i-B1 Backlight

Yes, no matter what I do, the 24V on each connector is always reading at 15.5V.

So you took out the two 24V pins off the connector (9101) that goes between the PSU and the main board, while the rest of the connector was plugged into the 9101 socket, and connector 9102 unplugged from the PSU? Posts 10 to 12 do not indicate this.

[0S1R1S]

Re: Vizio E500i-B1 Backlight

So you took out the two 24V pins off the connector (9101) that goes between the PSU and the main board, while the rest of the connector was plugged into the 9101 socket, and connector 9102 unplugged from the PSU? Posts 10 to 12 do not indicate this.

Okay, I removed connector C9101 from the power supply board. Plugged in to AC power. Forced on the TV and still only got 15.5V on the 24V rail feeding the LED driver.

[budm]

Re: Vizio E500i-B1 Backlight

Here is the marking to show how 12V and the 24V are generated.
As you can see, it is very simple, so it has to be something is being overlooked or measurement error.

[CapLeaker]

Re: Vizio E500i-B1 Backlight

If there would be something bad on the feedback circuit, I'd expect the 12V to be low too.
what if c9116 is shorted from 24v to GND, it should get a bit toasty.

[budm]

Re: Vizio E500i-B1 Backlight

If there would be something bad on the feedback circuit, I'd expect the 12V to be low too.
That is correct, something is fishy here.

[dick_barton]

Re: Vizio E500i-B1 Backlight

Lift out the jumper J9113 (lift on end) and measure the Cathode voltage of D9103 and of D9016 for 24V at each point

[budm]

Re: Vizio E500i-B1 Backlight

Oops, wrong thread.

[0S1R1S]

Re: Vizio E500i-B1 Backlight

Here's an update. The owner of the TV was impatient and told me to just order a power board. It arrived today (quick shipping) after ordering Friday. Plugged it in, plugged in AC power, and boom, it was working.

HOWEVER. The LEDs were flickering. Then steady. Then a little flicker. Then, now, they're gone. Completely. And we're back to 15.5V on the 24V rail on this new power board.

My only guess is something on the main board is back feeding to the power board and killing it.

[0S1R1S]

Re: Vizio E500i-B1 Backlight

Lift out the jumper J9113 (lift on end) and measure the Cathode voltage of D9103 and of D9016 for 24V at each point

I tried this and the voltages were still 15.5V on the center legs. On the outer legs, it showed 0V.

[0S1R1S]

Re: Vizio E500i-B1 Backlight

Also, I tested voltages as I was powering up, and the 24V rail would hit 16.8V, then drop.

[CapLeaker]

Re: Vizio E500i-B1 Backlight

Here's an update. The owner of the TV was impatient and told me to just order a power board. It arrived today (quick shipping) after ordering Friday. Plugged it in, plugged in AC power, and boom, it was working.

HOWEVER. The LEDs were flickering. Then steady. Then a little flicker. Then, now, they're gone. Completely. And we're back to 15.5V on the 24V rail on this new power board.

My only guess is something on the main board is back feeding to the power board and killing it.

Should have made measurements and compared the old board to the new board to see what's going on... too late for that now...
I am thinking too that there is something not right with the LED driver to start with, or even a bad LED. That doesn't fix the 24V rail on the PSU yet.

[0S1R1S]

Re: Vizio E500i-B1 Backlight

Should have made measurements and compared the old board to the new board to see what's going on... too late for that now...
I am thinking too that there is something not right with the LED driver to start with, or even a bad LED. That doesn't fix the 24V rail on the PSU yet.

Yeah, I made the assumption it was only a power board issue.
I'm giving up and I'm just going to wire in an internal/external 24V power supply to the LEDs and see how that works.