Acer Emachine 625 no display

[mohamed mm]

Hello everyone, I hope you all doing good,

I have Acer Emachine 625, working in good condition on external monitor (via vga port) but the internal display doesn't work, I tried it on other laptop and it worked fine but on the main laptop nothing.

after I checked I have found this:

Hall sensor

3.3v input, 3.3v output.

s i/o

3.3v on pin 105 (bkoff#)

dispoff#

0.25v I have checked this signal in similar laptop and it was 3.3v but in this laptop it's 0.25v, I have changed resistor but nothing happened, so I removed (diode) and the signal worked good 3.3v, but when I connect the internal display it blinked and show nothing.

I don't know what else I have to do.

help me If you can, I upload photo for diode and laptop schematic

Thank you.

[mcplslg123]

Re: Acer Emachine 625 no display

Whats about INVT_PWM/LCDVDD? The LID Switch is working ok and Disploff# should be 3.3V and you're right in your observation. Are you getting a dimm display on internal screen or no display at all??

[mohamed mm]

Re: Acer Emachine 625 no display

Thank you for help

INVT_PWM/LCDVDD? both are 0.0v

and there is no display at all

I have a question can s i/o work good at others function but bad in display section? like half good / half bad? or it's not related?

[mcplslg123]

Re: Acer Emachine 625 no display

Q22/23/25 voltage on all pins?? These models use LCD display perhaps with a inverter card for backlit. Does your model have this? If yes, then remove the card and see if you get dimm display. If yours is a LED display,ignore this part.

Sio can be partially bad. have seen that on many occasions when only one pin of sio is bad. However, in your case, its too early to judge a bad SIO.

[mohamed mm]

Re: Acer Emachine 625 no display

on Q22: there are 3.3v on two pins.

Q23: 3.3v on one pin.

Q 25: 3.3v on one pin.

I will attach photo to show you which pins has volts.

inverter card it is inside the LCD and it's working fine because I have tried the LCD on other laptop and worked fine.

Thank you.

[mcplslg123]

Re: Acer Emachine 625 no display

ENVDD is the gate for Q25 and seems present. Since this is N channel, high voltage at gate will allow the Source to pass on to drain-in simpler words, the ground from source will travel to drain. This in turn will not allow R348 to pullup 3V. This will pull gate of Q23 low,allowing Source to travel to drain(since its a p channel mosfet, gate should be low). So measurements indicates that you have LCDVDD present. However, you stated its not present.

can you clarify.

[mohamed mm]

Re: Acer Emachine 625 no display

I have measured (lcdvdd) from display jack and it read 0.0v.

and I have did that when monitor is connected and disconnected and in both gives 0.0v.

lcdvdd: 0.0v

INVT_PWM: 0.0v

DISPOFF# : 0.0v

what you are saying is correct there is power but for some reason the 3.3v is missing from ( lcdvdd, invt_pwm, and dispoff)

[Sephir0th]

Re: Acer Emachine 625 no display

There is pretty sure a measurement issue which lead us in circles right now. You can't have 3.3V at two pins of Q22 (one Pin is GND) and at Q25 only one pin with 3.3V. If Q25 Drain is pulled low, it should be the same at Q22 Gate. Repeat yxour measurements and share the correct values here.

[mohamed mm]

Re: Acer Emachine 625 no display

Thank you for your replay,

I am sorry I have made mistake,

Q23: two pins = 3.3v

Q22: one pin = 3.3v

Q25: one pin = 3.3v

lcdvdd = 0.0v

INVT_PWM: 0.0v

DISPOFF# : 0.0v

I have attached a picture and put green circles on the 3.3V output.

Thank you again