#2452 BLOC CTest: backlight doesn't turn off (B4-14 SHF72050046B)

[Zarro Boogs per Child]

#2452: backlight doesn't turn off (B4-14 SHF72050046B)
-----------------------+----------------------------------------------------
  Reporter:  Quozl     |       Owner:  wad     
      Type:  defect    |      Status:  assigned
  Priority:  blocker   |   Milestone:  CTest   
 Component:  hardware  |     Version:          
Resolution:            |    Keywords:          
  Verified:  0         |  
-----------------------+----------------------------------------------------
Changes (by wad):

  * status:  new => assigned

Comment:

 I'm checking to make sure that the fix to #1578 was included in 406_14,
 although if you only see this on one machine such an easy fix is unlikely.
 BTW, I recommend updating to 406_15 so that audio will work correctly.

 The B3 and B4 machines changed how the backlight was controlled.  In those
 machines we have to both turn off the brightness PWM (which is low pass
 filtered into a voltage, measurable across C599 --- unfortunately on the
 back of the motherboard, near the backlight connector CN28) and disable
 the power supply (by deasserting pin 4 of U9).

 Can you verify that pin 4 of U9 (located near the lower mesh antenna
 connector) is really being deasserted (low) when the backlight doesn't
 turn off ?

-- 
Ticket URL: <http://dev.laptop.org/ticket/2452#comment:3>
One Laptop Per Child <http://laptop.org/>