Vizio D55U-D1 No Picture

[macair1]

I am trying to troubleshoot a TV for a friend to save it from the landfill. When I turn on the TV, the screen is black. No LED backlighting. Tried the flashlight test but no picture. The front led indicator comes on.
Here are the voltages on the 16 pin connector on the power supply board.

TV plugged in but OFF:
+5V +12V +12V +12VA 3D_ON ON/OFF
5.17 19.10 19.10 19.10 0.00 0.00
5.17 19.10 19.10 19.10 0.00 0.00
+5V +12V +12V +12VA PS_ON DIM

TV plugged in and ON:
+5V +12V +12V +12VA 3D_ON ON/OFF
5.17 19.10 19.10 19.10 0.00 0.10
5.17 19.10 19.10 19.10 3.70 3.32
+5V +12V +12V +12VA PS_ON DIM

The voltage on the connector that powers the LED driver board and is marked on the power supply board as +24V reads as 22.1V when the TV is on (and 0 volts when it is off). On the Main board when the TV is off, LED401 is solid red. When the TV is turned on, LED 401 has both the blue and red LEDs on solid.

I do not see any bulging caps. The boards seem clean but the Main board has some fine powdery residue across much of it (but not on the back of the plastic housing). I was able to wipe the residue off with a pad with some isopropyl. The electrolytic caps on the main board are not blown or bulging.
The fuses on the power supply board are all okay. Cannot figure out if it is the power supply board (because I read 22.1V instead of 24V where it powers the LED driver board) or if it is something on the Main board. What do both the blue and red LEDs being on solid on the main board indicate?

Any suggestions on how to troubleshoot further?

Thanks.

[nomoresonys]

Re: Vizio D55U-D1 No Picture

Maybe unplug that connector then see if you have 24v.

[dick_barton]

Re: Vizio D55U-D1 No Picture

It would make for easier reading if you could give the connector number followed by the pin number, pin name and pin voltage
Eg

CN9101
Pin1 ON/OFF = ww
Pin 2 Dim = xx
Pin 3 Gnd = yy
Etc.

[macair1]

Re: Vizio D55U-D1 No Picture

Here are the voltages listed in a hopefully easier to read format.


CN9101: DC voltages when TV is plugged in but is OFF:
Pin1 ON/OFF = 0.00
Pin 2 DIM = 0.00
Pin 3 3D_ON = 0.00
Pin 4 PS_ON = 0.00
Pin 5 GND = 0.00
Pin 6 GND = 0.00
Pin 7 GND = 0.00
Pin 8 GND = 0.00
Pin 9 +12VA = 19.10
Pin 10 +12VA = 19.10
Pin 11 +12V = 19.10
Pin 12 +12V = 19.10
Pin 13 +12V = 19.10
Pin 14 +12V = 19.10
Pin 15 +5V = 5.17
Pin 16 +5V = 5.17

CN9101: DC voltages when TV is plugged in and is ON:
Pin1 ON/OFF = 0.10
Pin 2 DIM = 3.32
Pin 3 3D_ON = 0.00
Pin 4 PS_ON = 3.70
Pin 5 GND = 0.00
Pin 6 GND = 0.00
Pin 7 GND = 0.00
Pin 8 GND = 0.00
Pin 9 +12VA = 19.10
Pin 10 +12VA = 19.10
Pin 11 +12V = 19.10
Pin 12 +12V = 19.10
Pin 13 +12V = 19.10
Pin 14 +12V = 19.10
Pin 15 +5V = 5.17
Pin 16 +5V = 5.17


On the other connector that feeds the LED driver board, the voltage is 22.1V regardless of whether the cable is plugged in or not (whether there is a load or not).

Would it be worth trying my connecting a 24VDC to this cable using a separate 24VDC power supply just to see if the backlight comes on (the ground reference of this separate power supply would be different than everything else which is why I am not sure if its safe to try or not).

[dick_barton]

Re: Vizio D55U-D1 No Picture

Much easier to read and make sense of thanks.

It looks as though the ON/OFF (backlight control signal) is not being switched on by the mainboard .

It's 0.0V when TV is off and 0.01V when out of standby.

Disconnect the power supply from the mainboard and using a 1K resistor connect +5V to PS_ON and using a second 1K resistor connect +5V to ON/OFF. Switch on the power to the set and check if your backlights now come on.

[macair1]

Re: Vizio D55U-D1 No Picture

Thanks. If I disconnect the 16 pin cable from CN9101 (on the power supply board) that supplies power to the main board as instructed then I do not have +5V on pins 15 and 16 of CN9101 and hence do not have a 5V source to connect to PS_ON and ON/OFF via 1k resistors.

Are you suggesting that I use an external 5V supply for this test? As it appears to me that the 5V that I see on CN9101 pins 15 and 16 comes from the main board rather than the power supply board unless I am missing something.

[nomoresonys]

Re: Vizio D55U-D1 No Picture

Seems like something is wrong there, you should have the standby voltage on powerboard even with nothing else connected.

[macair1]

Re: Vizio D55U-D1 No Picture

Is the standby voltage +5VDC on pins 15 and 16 of CN9101? If that is the case, then any suggestions on how to troubleshoot the power supply board?

Thanks.

[nomoresonys]

Re: Vizio D55U-D1 No Picture

Not sure, this condition of only having the standby voltage with mainboard plugged is new to me, is it a different design maybe??

[budm]

Re: Vizio D55U-D1 No Picture

The Backligts controls is done directly between main board and the LED driver board, see the connector CN805 on the left side of the LED driver board that goes to the main board.
BTW, Do you get 12VDC on the T-CON fuse when TV is turned on?
What happen if you disconnect WiFi card?

[nomoresonys]

Re: Vizio D55U-D1 No Picture

Ah I see, thanks Bud, that will teach me to look at the pictures first. lol.

[macair1]

Re: Vizio D55U-D1 No Picture

Thanks budm. Disconnecting the WiFi card makes no difference. I have no voltage on the 5A T-CON fuse F1 when the TV is turned on and I checked and the fuse is good.

[budm]

Re: Vizio D55U-D1 No Picture

Main board problem, probably EEPROM.
https://www.shopjimmy.com/vizio-756t...eprom-only.htm
Notes from Shopjimmy:
IMPORTANT:
These main boards can have multiple failures, in addition to the EEPROM.
If EEPROM replacement does not repair your board, there are likely additional problems.

Symptoms EEPROM replacement MAY fix:
- TV turns on but there is no backlight

[neilc6]

Re: Vizio D55U-D1 No Picture

ON/OFF signal not coming from processor. Bad BGA connections. Common problem in Vizios. Not a eeprom problem. Shopjimmy is wrong.

https://www.badcaps.net/forum/showthread.php?t=76708

[budm]

Re: Vizio D55U-D1 No Picture

Pin1 ON/OFF = 0.00
The ON/OFF for this model is not routed through the power supply board, the backlights controsl are routed directly from the main board to the LED driver board.
And since the MICOM also not sending the control signal to turn on the switched 12V for T-CON either, so it may not be just EEPROM problem that is why the Notes form SJ shows:
IMPORTANT:
These main boards can have multiple failures, in addition to the EEPROM.
If EEPROM replacement does not repair your board, there are likely additional problems.

[macair1]

Re: Vizio D55U-D1 No Picture

Thanks Neilc6 very much for your very helpful input. I used the suggestions from the link you provided. Used a hot air station first to try and heat up both the BGAs on the main board at 800 deg F for 45 sec each from about an inch away (did not want to overdo it the first time!). That did not help.

Then used a heavier duty regular heat gun cranked to 980 deg F and just heated up the top BGA area on the heatsink for 45 sec. Had missed the note in the link about just doing the north which I assume meant the top BGA chip the first time around. Tried to power it up, and the backlight came on and the TV functions fine (for now!). So the problem is definitely the main board and the BGA connections.

I then checked the voltages in case it helps someone else with the same problem. All voltages match my original documented voltages except for the ON/OFF on CN9101 which is now 3.178V instead of 0.10. Fuse F1 on the TCON now has 12VDC on it as Budm indicated it needs to be. Incidentally, the voltage going to the LED driver board is still 22.1V. So even though that is labeled on the board as being 24V, in reality it is just 22.1V.

Thanks again everyone for helping.

[budm]

Re: Vizio D55U-D1 No Picture

Thanks for the follow-up, it may or may not last with heating method due to thermal cycle, you may want to add cooling fan to keep BGA cool.
BTW, regarding the ON/OFF signal on power supply connector CN9101, that on/ff and the dim signals are not routed to the power supply connector CN9201/0203 that goes to the LED driver board, as you can see there are no wires for those two pins.

[nomoresonys]

Re: Vizio D55U-D1 No Picture

Thanks for the follow-up, it may or may not last with heating method due to thermal cycle, you may want to add cooling fan to keep BGA cool.
BTW, regarding the ON/OFF signal on power supply connector CN9101, that on/ff and the dim signals are not routed to the power supply connector CN9201/0203 that goes to the LED driver board, as you can see there are no wires for those two pins.

+100 on the fan for sure.

[macair1]

Re: Vizio D55U-D1 No Picture

Thanks Budm and Nomoresonys. Any suggestions on how to install the fan as there does not seem to be much clearance between the heatsink and the back housing for a fan to be installed on the heatsink?

Would you advice powering the fan from an external power source or inside the tv?

Thanks again.

[nomoresonys]

Re: Vizio D55U-D1 No Picture

A few ways to do it, one is make a hole in the back cover where the bga is located and add a fan to the cover, another is add 2 fans one pulling air into bottom another blowing hot air out at top, there's some videos on youtube if you can hunt them down, example there at amazon of a 2 fan solution: https://www.amazon.com/Plasma-Vertic.../dp/B011LYNCYO