Logic Board Test Points

Some test points are accessible on the logic board when the LCD panel is removed. The test points are defined below.

Logic Board Test Point

Function

 

 

Pin 1

Ground

 

 

Pin 3

5V power for Hard Drive(s). Note: If present, the 12V power will

 

come directly from the Power Supply to the Hard Drive thru the

 

power harness cable.

Pin 4

Standby 12V power (permanent power coming from power

 

supply and present as long as AC cable is connected, even if

 

computer is off); corresponds to LED #1

 

 

Pin 6

Backlight Control pulse width modulated signal (from logic board

 

to LED backlight board, to adjust the backlight level setting

 

according to user setup)

 

 

Pin 11

12V Run-Mode power to logic board (coming from power supply,

 

present as long as system is on or asleep); corresponds to LED #2

 

 

Pin12

Power On Request signal (from logic board to power supply

 

when power button is pressed)

 

 

Pin 13

Backlight Enable (signal from logic board to Backlight Controller

 

board, to enable backlight

 

 

2010-09-09

iMac (27-inch, Mid 2010) — General Troubleshooting 32

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Image 32
Apple MD094LL/A manual Logic Board Test Points, Function, According to user setup, Pin, Board, to enable backlight