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Can I ask about an Alienware in here?

daxxone

daxxone

Member
M18x R2 that isn't turning on the LCD backlight. Tried switching GPUs, LCDs, LVDS cables. Found schematics with a search of 'Compal LA-8321P' and found page 24-25 cover LCD baclight, LVDS connector. This doesn't have signs of damage. System functions normal besides this one problem. Any help would be great. What do you need me to test?
 
2informaticos

2informaticos

Administrator
Staff member
Do you get image, only missing backlight?
Backlight enable and adjust (PWM) come out from U7 multiplexer.
Check some voltages for U7, like pins 16, 7, 9, 2, 14.
Also check +INVPWR_B+ presence at JLVDS.
Need to check signals and voltages with LCD connected, of course.

Some components, marked with @, are optional.
Depending of which ones you have on the board, you should follow corresponding signals and voltages...
 
daxxone

daxxone

Member
Testing Q45 again.
Pin 1: 0.05 climes to 1.15
Pin 2: 0.05 climes to 1.15
Pin 3: 19.00
Pin 4: 19.56
Pin 5: 0.05 climes to 1.15
Pin 6: 0.05 climes to 1.15

R423:
Pin 1: 19.00v
Pin 2: 0.0v

Q44: (Data sheet has different pin numbers than the laptop schematic so I just labeled the source, gate, and drain)
Pin G: 3.3v
Pin S: 0.0
Pin D: 0.0
 
daxxone

daxxone

Member
Diode mode test +INVPWR_B+ (LCD connected) gave me nothing.

Gate to source has low resistance at .758
R423 is at 48k
I tested this same P MOSFET on a scrap Alienware 17 Ranger I have ( used the same circuit design according to the schematics for it 'compal LA-9331P' ) Gate to source resistance should give no response in diode mode?
I'm still pretty green when it comes to circuit toubleshooting, but if I've understood this right so far, I can swap this Q45 tonight and have this board ready to go back into this system.

Thanks for taking time to help me with this.
 
B

Biggtechman

Member
Had this exact same issue on an LA-8321P also, this thread helped me fix it! Replacment also taken from a scrap Alienware 17 Ranger. Thanks. :-)
 
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