Vizio e400i-b2 turns on backlights flash

[nwcs]

I verified via time lapse video that all of the backlights light up when turned on. Voltage to the backlights are 37v at turn on then down to 32v. If I unplug the backlights from the backlight power board above the power supply then the voltages stay at 37v. I did notice that the tv turns itself off after a few seconds, or at least appears to. The voltages from the ps to the main are all correct when turned on but then all but pin2 5vsb and pin 3 pson 3v go to either 0v or 1v. I believe it is the main board that is causing the issue. Does anyone have any other Idea or agree?

[dick_barton]

Re: Vizio e400i-b2 turns on backlights flash

Have you measure the voltages going to the leds? Could you spply more pictures of individual boards which would be of help.

[nwcs]

Re: Vizio e400i-b2 turns on backlights flash

Yes when the led are plugged in I get 32v if I unplug them I get 37v. The correct voltage is 37V.

[nwcs]

Re: Vizio e400i-b2 turns on backlights flash

I am not at my store right now but there are only 3 boards, main, ps and tcon which is part of the lcd panel.

[budm]

Re: Vizio e400i-b2 turns on backlights flash

What DCV do you have on CN1 connector of the LED driver board?
http://www.shopjimmy.com/vizio-55-76...ed-driver.htm#

Vizio 55.76N04.A01 (48.76N09.01M) LED Driver
Pictures provided by shopjimmy.

[nwcs]

Re: Vizio e400i-b2 turns on backlights flash

i am not at my store right now but will check on monday.

[SLK001]

Re: Vizio e400i-b2 turns on backlights flash

That's the LED controller going into protect mode. You have bad LEDs in your panel.

[nwcs]

Re: Vizio e400i-b2 turns on backlights flash

that is what I would normally think but I can see thru time lapse video that all LED's are lit up.

[budm]

Re: Vizio e400i-b2 turns on backlights flash

It looks like Q5~9 are the PWM controlled power MOSFET's, the big tab should be the Cathode return of each LED string.
Put the black probe on the chassis GND, red probe on Q5 big tab, turn the TV on and watch to see how high the DCV goes up too, then wait and see how low it will go down to, record those readings.
Then turn the TV off and then do the same thing again on big tab of Q6, same thing for the Q7~9.

[nwcs]

Re: Vizio e400i-b2 turns on backlights flash

connector CN1 when led's are connected to led driver board I get 25V then the led's flash then drops down to 0v. When disconnected I get 25V then when it shuts down I get a drop to 0v. Q5 big tab goes to 9.5v when turned on the back down to 0v. Q6 thru Q9 9.44v then down to 0v.

[budm]

Re: Vizio e400i-b2 turns on backlights flash

That CN1 is the input Voltage to feed that LED driver board Boost converter circuit (L1, Q1, D3, TC2~4), I do not expect that input Voltage to drop out. The BL-ON control signals is usually used to turn the Boost converter ON or OFF not the Voltage feeding the boost converter circuit.
I need to look further on how that 25V is generated by the main power supply and see if there is protection shutdown circuit for that 25V power supply.

[budm]

Re: Vizio e400i-b2 turns on backlights flash

BTW, which one of the power supply board do you have?
http://www.shopjimmy.com/catalogsear...Vizio+e400i-b2

Vizio 56.04115.002?
Vizio 56.04115.003 (OPVP-0217)?
BTW: what is the dcv rating of the caps TC2~4?

[nwcs]

Re: Vizio e400i-b2 turns on backlights flash

Just saw your post so I took a picture of of the power supply label. A lot more information that way.

[nwcs]

Re: Vizio e400i-b2 turns on backlights flash

I forgot to post the voltages of tc2~tc4, 32v with led's disconnected and if connected drops down to 0v. The ps pn is 56.04115.041. I am hoping it is the led drive board since that would be a cheap fix.

[SLK001]

Re: Vizio e400i-b2 turns on backlights flash

Check the connection between the PS and the LED drive board. On the PS side, they have a tendency to fracture the solder joints. If so, remove all the lead-free crap and put down some 60-40.

[nwcs]

Re: Vizio e400i-b2 turns on backlights flash

The solder looks good but I put new solder in anyway and no change.

[budm]

Re: Vizio e400i-b2 turns on backlights flash

Vizio 56.04115.041 (OPVP-0217) Power Supply Unit

http://www.shopjimmy.com/vizio-56-04...pply-unit.htm#

So you have indicated that the switched 24V on CN202 that goes to the CN1 of the LED driver board drops down to 0V. How about the switched 12VDC on CN201, does it drop out also?
If trace out the board you can see that the Main power transformer T101 generates the 5VSTBY, switched 12V output (MOSFET Q202 is the switch), switched 24v (MOSFET Q207 is the switch).
Both Q202, Q207 Gates are driven by Q205, this Q205 gets the turn on signal at the PS-ON pin from the main board.
The 12V is fed to linear regulator Q206 to produce the the 5VSTBY.
So see if the 12V is still present when the 24V drops down to 0V.
For the switched 12V and the switched 24V to drop out, the PS-ON has to drop to <1VDC, and since we know that the 5VSTBY does not drop out then we know that it is not in the T101 drive circuit is the problem otherwise the 5VSTBY will shutdown also and kill the whole circuits.
Pictures provided by shopjimmy.

[nwcs]

Re: Vizio e400i-b2 turns on backlights flash

Yes the 12v on cn201 does drop to 0v with the led's connected.

[budm]

Re: Vizio e400i-b2 turns on backlights flash

So look to see if the PS-ON also drops too then? as indicated in post 1?
BTW, I do not any error out signal pin on the power supply board to tell the main board to shutdown the PS-ON signal if there is problem with backlights circuit, the only one I see is the AC-DET pin that you may want to check and see.

[nwcs]

Re: Vizio e400i-b2 turns on backlights flash

No, the ps-on does not drop but ac-det does drop