3662 no bklt

[Rford]

Have a 3662 with display, but no backlight. U7701 has bklt_en_r u7750 has no voltage on bklt_en_r_jerry... Display works on exterior monitor, soup was spilled on device, but shop sent it through USC, so no evidence of corrosion. Looks clean. have 5 v at L8300 too

 

[larossmann]

What voltage is SMC_LID?

What is backlight output on pin 1 of LCD connector? 0v, 12.6v, or 50v?

What is voltage on pin 3, 4, and 5 of Q7706?

 

[Rford]

Q7706
p3:10.14
p4:10.5
p5: 0

j8300:
p1: 0v

smc_lid:0

 

[larossmann]

Well there you go it thinks the lid is closed. When closed, no backlight!

SMC_LID is 3.42v or so when the machine is open, and 0-0.5v when the lid is closed. So if SMC_LID is 0v, there are a few possibilities I will list in order of likelihood.

1) J5250 area has corrosion on it, around PP3V42_G3H this is where lid sensor attaches that detects the magnet in the screen assembly to tell the machine it is closed. Remove and check.
2) R5250 is bad or corroded
3) R5171 is bad or corroded
4) Q4801 is bad(highly unlikely but happened once)
5) You are measuring the machine closed, so it is giving 0v on SMC_LID for good reason(please tell me you weren't doing this).

 

[Rford]

Alright man, here's the thing, I have theboard out of the machine. Lid is of course open according to that Hall effects switch. However I did have a neo-d magnet that was next to it. It's for holding screws. I don't think I could replicate it again if I tried. Smc_lid is 3.42 now. (Palms face). R5250 and r5271 are fine... so 0v on p1 of LCD connector, smc_lid=3.42, q7706 p3:10.14, p4 10.5 and pin 5: 0v.

 

[Alan.L]

you need to have a screen connected in order to measure voltages.

 

[Rford]

Yep there was

 

[Rford]

Does it sound like it could be the display? I will be getting a test screen soon, but I wonder if U7750 not being energized would cause the issue. larossmann dukefawks

 

[dukefawks]

Is there an image on the LCD? Hold flashlight to the Apple logo.

 

[Rford]

Yes, well it's the folder with a question mark

 

[dukefawks]

Check for corrosion around U7701/7750. Replace them if no corrosion present.