BN44-00496B A5V only have 2.2V

[dick_barton]

Re: BN44-00496B A5V only have 2.2V

Use your meter in diode mode and check between Source/Drain of the FDD7N25LZ. You should be able to measure the diode across the internal package. High one way, low reading when leads reversed.

[jeremykum]

Re: BN44-00496B A5V only have 2.2V

Use your meter in diode mode and check between Source/Drain of the FDD7N25LZ. You should be able to measure the diode across the internal package. High one way, low reading when leads reversed.

Black = drain
red = source
0.480v

reverse it, 0v

[jeremykum]

Re: BN44-00496B A5V only have 2.2V

BTW I did some test.

I remove 3 diodes in red circle, and I get 190VDC at LED socket D1/DI
Checked these 3, all ok, diode test same reading.

Soldered it back, I get 50VDC

Means anything to you guys?

[dick_barton]

Re: BN44-00496B A5V only have 2.2V

Black = drain
red = source
0.480v

reverse it, 0v

That looks fine except "0V" is probably "OL" = meaning no voltage reading not 0V reading.

[jeremykum]

Re: BN44-00496B A5V only have 2.2V

That looks fine except "0V" is probably "OL" = meaning no voltage reading not 0V reading.

I am not sure totally sure, but so far this didn't give indication of total failure though.

[budm]

Re: BN44-00496B A5V only have 2.2V

On this board, this L shoud be L9801. Removed. Still 2.2V at A5V
The filter cap for 13V register 0v. Circuit checked, not grounded.

Q9101, should be the big N-Chan mosfet FDD7N25LZ, measured with DCA meter, seems working. Source and drain, one way register 11.2Mohm, the other way 0 (if continuity mode, no beeping).

That 13V is generated by the same transformer that generate the 5V and other Voltages, and the cap I suggested to test the Voltage is right after the rectifiers for the 13V BEFORE the switch so it cannot be 0V unless the schematic does not match the board, that schematic looks to be made by reverse engineering so it i may not be accurate.

[jeremykum]

Re: BN44-00496B A5V only have 2.2V

I ordered a replacement board. Same codes, but rev number is 1.1 instead of 1.2 on the problematic psu board.

All voltage is alive and within limits. However the power button on the tv would not fire up the tv. No backlight, nothing. I notice the main chip on the motherboard is slightly warm, I assume nothing is wrong.

I tried disconnecting the mother ribbon connection to psu board. Switch on the mains, the led light up. Connect it back, and cannot power on.

Any ideas?
Is it firmware related?
Anyway, the remote is not with me at the moment, already inform the owner to send it to me asap.

[jeremykum]

Re: BN44-00496B A5V only have 2.2V

some updates

At this connector, those with voltage symbols all have the respective volt.

and...

Power On/Off - 3.50v
Pwm Dim - 0
BLU on/off - 4.85v

[budm]

Re: BN44-00496B A5V only have 2.2V

"Pwm Dim - 0" You will not get the backlights to be on with Dimming control at 0 V.
Turn the TV off, then put black probe on the chassis, Red probe on the Dim pin, then turn on the TV to see if there is any activity with the Dim control signal or not.
We also need the pictures of the whole back side of the TV showing all the boards.
BTW: These Voltages below, do they change state when power switch is toggle on and off?
Power On/Off - 3.50v
BLU on/off - 4.85v

[jeremykum]

Re: BN44-00496B A5V only have 2.2V

"Pwm Dim - 0" You will not get the backlights to be on with Dimming control at 0 V.
Turn the TV off, then put black probe on the chassis, Red probe on the Dim pin, then turn on the TV to see if there is any activity with the Dim control signal or not.
We also need the pictures of the whole back side of the TV showing all the boards.
BTW: These Voltages below, do they change state when power switch is toggle on and off?
Power On/Off - 3.50v
BLU on/off - 4.85v

Those 3 voltages doesn't change when pressing the power on button.

[HABIBOU11]

Re: BN44-00496B A5V only have 2.2V

Thank you