iMac (27-inch, Mid 2010) Symptom Charts — Startup and Power 35
2010-09-09
Symptom Charts
Follow steps in the order indicated below. If an action resolves the issue, retest system to verify.

Startup and Power

No Power, Dead Unit

Unlikely cause: speakers
Quick Check
Symptoms Quick Check
No Power, Dead Unit
• No power
• No fan spin
• No startup chime
• No image on external display
• No hard drive or optical drive
activity
• Caps Lock LED on wired
keyboard doesn’t light when
pressed.
1. Verify power source.
2. Verify power cable.
3. Listen closely for signs of activity from system
including: rotating fans, hard drive or optical drive
activity, startup chime, etc.
Deep Dive
Check Result Action Code
1. Power ON system. Verify if
there is any indication that the
system has powered up (fan
rotation, hard drive or optical
drive noise, backlight turns on).
Yes The symptom is powering
up. Go to Won’t Start Up
symptom ow.
No Go to step 2.
2. Locate the diagnostic LEDs
in bottom case vents. Plug
AC cord into system. Verify if
diagnostic LED #1 turns ON.
You may alternately check for
presence of a 12V DC signal
between pin 4 and pin 1 of the
logic board.
Yes Standby power voltage being
supplied by power supply.
Go to step 3.
No Go to step 4