Vizio V505-G9 PS ok, voltage disappears near power connector on Main Board

[DXseekerMO]

Hello everyone. I picked up a Vizio V505-G9 the other day. There's no status indicator light action at all and it will not turn on.

As it appears this is the first thread on this model I have uploaded a real good set of pix so we can see how everything is laid out.

I tested the power supply and it does have the appropriate voltages where they should be, but no PSon voltage was found and pressing the power button made no difference.

So I started tracing the 12V circuits upon the Main Board that come from the Power Supply only to find these voltages seem to "disappear" quickly. Furthermore there's no output power to the IR board, button board and only .2V to the Wi-Fi module. No power at EEPROM UL1 either.

As I continued I ran across an IC bearing the marks "KCI04e 4459" and located a datasheet for a 30V P-channel MOSFET. Upon testing the item the voltages were as follows:

All Source pins: 12.03V
Gate pin: 11.97V
All drain pins: 0V

So guys if I'm seeing this right, this MOSFET looks like it's internally shorted to GATE, or something in-circuit with this MOSFET is short causing it to look shorted? What do you think?

[R_J]

Re: Vizio V505-G9 PS ok, voltage disappears near power connector on Main Board

That mosfet looks like it supplies the voltage for the t-con/panel try disconnecting that cable and see if the tv turns on (without video)
Does the modfet get warm?

[DXseekerMO]

Re: Vizio V505-G9 PS ok, voltage disappears near power connector on Main Board

That mosfet looks like it supplies the voltage for the t-con/panel try disconnecting that cable and see if the tv turns on (without video)
Does the modfet get warm?

Disconnect LVDS, no change in status.

The MOSFET does not appear to be getting hot. It does not check short between source and gate with a meter.

[R_J]

Re: Vizio V505-G9 PS ok, voltage disappears near power connector on Main Board

On the back of the main board, there should be 5V_STB and 3V3_STP test points

[dick_barton]

Re: Vizio V505-G9 PS ok, voltage disappears near power connector on Main Board

The mosfet is a P channel mosfet and I believe that if the gate voltage is at the same level as the source then it is in the OFF state. Hope i've got that right.

[budm]

Re: Vizio V505-G9 PS ok, voltage disappears near power connector on Main Board

The mosfet is a P channel mosfet and I believe that if the gate voltage is at the same level as the source then it is in the OFF state. Hope i've got that right.

+1
The Gate Voltage of that P-CH MOSFET has to about 3~4 V less than Source pin Voltage for the MOSFET to be on.

[DXseekerMO]

Re: Vizio V505-G9 PS ok, voltage disappears near power connector on Main Board

On the back of the main board, there should be 5V_STB and 3V3_STP test points

Thanks R_J, no voltage is present at the stand-by voltage test poiint

The mosfet is a P channel mosfet and I believe that if the gate voltage is at the same level as the source then it is in the OFF state. Hope i've got that right.

+1
The Gate Voltage of that P-CH MOSFET has to about 3~4 V less than Source pin Voltage for the MOSFET to be on.

Thanks dick_barton and budm! Looks like that MOSFET is likely working then.

[R_J]

Re: Vizio V505-G9 PS ok, voltage disappears near power connector on Main Board

Those standby regulators get input voltage from somewhere, and the only source is the 12v input to the board, so there must be something open.
That 4459 mosfet seems to be the switch for VCC_PANEL (panel supply voltage)

[R_J]

Re: Vizio V505-G9 PS ok, voltage disappears near power connector on Main Board

Next to the 220µf/16v, closest to CN4, there is a black smd (ED1). Could this be a fuse or 0Ω resistor? There is another one near the 8 pin smd. They seem to have one end on the 12v trace, does the other end connect to the input of the ldo ic's ? or go to ground?

[DXseekerMO]

Re: Vizio V505-G9 PS ok, voltage disappears near power connector on Main Board

I found a Main Board for $7.48. If the problem wasn't this MOSFET I was going to replace the board. A time vs money issue.

I will report back after I install the board and let you know how it turns out!

[DXseekerMO]

Re: Vizio V505-G9 PS ok, voltage disappears near power connector on Main Board

The mosfet is a P channel mosfet and I believe that if the gate voltage is at the same level as the source then it is in the OFF state. Hope i've got that right.

+1
The Gate Voltage of that P-CH MOSFET has to about 3~4 V less than Source pin Voltage for the MOSFET to be on.

Next to the 220µf/16v, closest to CN4, there is a black smd (ED1). Could this be a fuse or 0Ω resistor? There is another one near the 8 pin smd. They seem to have one end on the 12v trace, does the other end connect to the input of the ldo ic's ? or go to ground?

Ok so the replacement Main Board showed up. The TV now turns on and the screen is intact. Unfortunately the left side of the screen from just to the right of center is significantly darker than the right side. The on-screen display on that side also has image retention and much less definition than the right side.

Ordinarily I'd start checking the screen at this point, but as I was going through the set-up I noticed upon the right lower part of the screen a version number LINIXUKV. This crosses to a model# D50x-G9. According to Encompass.com the main board for that model is a different part number than my V505-G9 serial LINIXXKV. That could mean this Main Board is incompatible with my LCD. Furthermore after set-up the progress circle spins without ceasing upon the screen so it looks like a bust anyhow.

At any rate I'm trying to reach the seller who hasn't responded to my message in 36hrs. It is the weekend. We'll see what happens tirdmorrow.

[nomoresonys]

Re: Vizio V505-G9 PS ok, voltage disappears near power connector on Main Board

Wonder if it's a bad/loose tab bond.

[DXseekerMO]

Re: Vizio V505-G9 PS ok, voltage disappears near power connector on Main Board

Well finally this TV decided to stop getting "spun" and I finally got a picture after the factory reset. The left side was still "slim shady".

End game: The display panel part number from both TVs are identical, and unfortunately the left lower corner of the LCD is just barely damaged, causing the Marshall Mathers appearance on that side.

So the real slim shady finally stood up. Will someone please let Eminem know?