No power Benq G922HDAL

[srbax]

Re: No power Benq G922HDAL

I removed voltage regulator on logic board and it's not shorted.
Between 3.3 V pins and I pad is 0.9 ohms and 3.3 V pins and G pad is 8.8 ohms.
Other boards are detached.
Is this normal results or I have shorted logic board and it's time to give up on this monitor?

[srbax]

Re: No power Benq G922HDAL

I made it to find voltage regulator and replaced bad one on power board.
I replaced it with lm3940imp-3.3. Now there is 3.3 V out of power board.
When I connected all boards and monitor to pc it won't work.
I measured voltages on connectors for other two boards:
CN701
pin1=3.28V
pin2=3.28V
pin3=5V
pin4=5V
pin5=0
pin6=0
pin7=0
pin8=0
pin9=0
pin10=0

CN702
pin1=16.76V
pin2=16.76V
pin3=0
pin4=0
pin5=0
pin6=0

Voltages on voltage regulator on logic board:
I=3.23V
G=0V
O=1.83V

PC recognizes monitor but power led is not working at all, and backlight too.
There is no reaction when I'm pressing power button.
Voltage on power button is 3.19V.

Any ideas?

[selldoor]

Re: No power Benq G922HDAL

Have we got a picture of the board the led backlights connect to?
In Pic 3 there is a white fuse 3A - have you tested this, please post result in ohms.

[srbax]

Re: No power Benq G922HDAL

Yes, it is picture 3.
I tested it before: 0,8 ohm.

[srbax]

Re: No power Benq G922HDAL

I also measured 16,7 V on testing points near connector for backlight on that board

[selldoor]

Re: No power Benq G922HDAL

I would guess that on the connector on that board and cn702 the reds are connected together and are the V+ The two black wires are both ground - can you check that.
The green and white one will probably be back lights (leds) on/off and the other will be dim. I am wondering if you can apply an external 3v to the on/off if the lights will come on?

[srbax]

Re: No power Benq G922HDAL

You are right about red and black wires.
I don't have external 3V power to apply.
Something else to check?

[srbax]

Re: No power Benq G922HDAL

Can I try it with Fluke?
It gives 2,4V in diode test.
When I tried to test power leds with Fluke they turned on and fluke was on beep.
I don't know what voltage is applied in that case.

[selldoor]

Re: No power Benq G922HDAL

Sorry - no idea either- dont own a fluke.
Perhaps 2 x1.5 batteries or a 3v cr2032?

On another tack have you tested what I think is the buttonboard cable a flat ribbon 7 connectors on the main board- Clean the connection - make sure it is in the right way and check the traces for continuity - also find which pin/s are the on/off and perhaps a pic of the button board?

[srbax]

Re: No power Benq G922HDAL

I checked cable for continuity and connectors are clean and on right way on their place.
Also power button looks fine. I checked it with beep sound and there was beep when I pres the button.
All resistors has good values on button board.
On picture of logic board I wrote values of voltages.
On third pin there is variation of voltage from 0.4-0.8V.
I assume that is on/off pin. Are those variations normal?
It looks like that pin is connected to transistor below that pin.
On other two pins is stable 5V.
Are those two transistors maybe start-up transistors and could one of them be bad?

[srbax]

Re: No power Benq G922HDAL

I was pushing all the buttons and something strange happened.
After pressing 'menu' button monitor powered up!?
There was a message 'no cable connected'. After connecting vga cable there was a message 'no signal'.
After that monitor goes to sleep mode. I can awake it with enter, auto and menu button.
On pin with variable voltage after powering up there is 1.2V and pin below on picture there is 2V.
In sleep mode is vice versa, only 1.2V is now 0.8V.
I want to mention that is still 9 ohm between 3.3V and gnd.
Backlight is working.
Any ideas?

[selldoor]

Re: No power Benq G922HDAL

If you have it come on again try in the menu to find a factory reset option.
That may help sort itself out. - maybe the data on the eprom is corrupt.