Apple iMac A1419 27" Retina 5K MID 2015

[mferna14]

Hi all, working on an Apple iMac A1419 27" Retina 5K MID 2015 Logic board 820-01134-A. No Display, power supply turns on fine. There are 5 diagnostic LED on the logic board. Only 2 are lit now & no display. Power is fine. Does anyone konw the diagnostic status on these LEDs. & anyone can help sharing the Shematics & Boardview for this model 820-01134-A. Much appreciate anyone help. Thanks

[andyapple]

Re: Apple iMac A1419 27" Retina 5K MID 2015

LED 1
Indicates that the trickle voltage from the power supply has been detected by the main logic board. This LED will turn
on when you connect the iMac to a working AC power source. The LED will remain on as long as the computer is on or
asleep.
When the computer has been shut down correctly, LED 1 behavior may differ:
If a startup event is scheduled in System Preferences/Energy Saver, then LED 1 will stay on after a correct
shutdown.
If no startup event is scheduled in System Preferences/Energy Saver, then LED 1 will turn off and will stay off as
long as the power cord is kept connected and an AC power source is present. Disconnecting the power cord and
plugging it back in will turn this LED back on, even if the computer is still off.
After disconnecting and reconnecting the AC power source, this LED could remain off:
If the AC power source is missing or disconnected.
If the logic board is disconnected from the power supply or the AC receptacle.
If the power supply board is faulty.

LED 2
Indicates that the computer is turned on. This LED will be on as long as the computer is turned on (but is not asleep)
and the power supply and voltage regulators are working correctly.

LED 3
Indicates that the logic board and GPU are communicating. This LED will be on when the CPU is communicating
properly with the GPU. If LEDs 1 and 2 are on and LED 3 is off, then the backup battery (on the back of the logic
board) may need to be reseated or the logic board may need replacement.

LED 4
Indicates that the logic board and LCD panel are communicating. This LED will be on when the computer is turned on
and a video signal is being generated. If LED 4 is on and there is no image on the display, then the LCD panel or the
cables between the LCD and logic board might be installed incorrectly or need replacement.

LED 5
Indicates the logic board and LCD panel are communicating. This LED is on when the computer is turned on, a video
signal is being generated, and the LCD Panel is signaling to turn on the backlight. If LED 5 is ON and there is no image
on the display, then the LCD backlight or circuitry on the logic board may be malfunctioning. The LCD panel or the
cables or the logic board may need replacement.

[mferna14]

Re: Apple iMac A1419 27" Retina 5K MID 2015

Thank you so much for all this added knowledge., really appreciate your help in all this research.

[Katz993]

Re: Apple iMac A1419 27" Retina 5K MID 2015

Having a similar issue, did you ever have any luck?