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820-00138-05, no backlight

H

Hardwood T/S

Member
Hey guys! New forum style, neat. Haven't been here in a while lol.

So I've been dealing with this guy for a while--original problem had no backlight, had some liquid damage around backlight chips/lvds connector, cleaned 'em up and resoldered new connector. Have image, but still no backlight.

Noticed pin 3 of Q7706 (LCDBKLT_EN_L) wasn't low enough (12.93v), but resistance showed good between pin 3/4 of Q7706 and of R7701 (80.6K) and had 3.3v on BKLT_EN_R. Ran wire from BKLT_SD to ground to see if I'd get backlight, still nothing but now LCDBKLT_EN_L is proper 5.5v and 1/2/5/6 Q7706 (PPBUS_SW_BKL) is 13.06v, passing thru PPBUS_G3H. PPBUS_S0_LCDBKLT_PWR_SW and PPVOUT_S0_LCDBKLT are ditto, 13.06v.

I believe I read that this is due to something with Q7701 being off? But that thread referenced a situation where BKLT_SD didn't have to be manually shorted, and I couldn't find much else, so I offer this to you guys. :)
 
2informaticos

2informaticos

Administrator
Staff member
First, remove the ground wire from BKLT_SD.
Post BKLT_SCL/SDA voltage and diode mode to ground.
Did you try another compatible LCD assembly?
 
H

Hardwood T/S

Member
PRAM reset had what looked like a small flash on the screen right after the first or second reset, but nothing afterwards.

LCD_BKLT_PWM_R - 3.2v
 
H

Hardwood T/S

Member
Got it working :) resoldered L7710 and Q7701, we have backlight.

Unfortunately, after a while of the board being turned on and functioning totally normally, the system hung for a moment and fans went up, and now the fans blare shortly after turning the computer on--classic PFM006, NDC001, PPN001. It's probably the I/O board cable as I saw it had some corrosion on one end--will replace and update with if it fixed.
 
H

Hardwood T/S

Member
New update: not sure if this is related or just a quirk of the issue, but the computer runs fine with only one fan installed. No slowdowns, no fan blurs, nothing. With both fans plugged in, however, the computer quickly picks up their speed and runs very slowly.

edit - now it's slow with one fan plugged in again. Confused as to why it's working differently some times rather than others.
 
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H

Hardwood T/S

Member
Does this indicate anything specifically? From what lines I see that are associated, none are shorted--though I didn't test their voltages yet. Will give a more detailed update when flatcable comes in.
 
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