iMac (21.5-inch, Late 2009) Symptom Charts — Display 45
2010-11-18
Noise / Unstable Flickering
Unlikely cause: camera, microphone
Quick Check
Symptoms Quick Check
Noise / Unstable Flickering
• Unstable image
• Flickering image
• Humming noise from display
• High frequency noise from
display
1. Verify that intake vent on bottom of computer is
not obstructed.
2. Inspect system for third party software that is
being used to set fan speeds to a higher than
normal RPM. Some users may install this software
to monitor and control internal temperatures,
potentially causing higher fan speeds to generate
higher than expected noise levels.
Deep Dive
Check Result Action Code
1. Verify if user issue is due to
ickering, or to an unstable
video image on the LCD.
Yes Suspected ickering issue, go
to step 2
No For audible noise issues go to
step 8. All other issues go to
appropriate symptom ow.
2. Connect a supported external
display to the mini DisplayPort
on rear of computer. Verify
if issue occurs with external
display.
Yes Suspect issue with video
circuitry. Go to Corrupted
Video symptom ow.
No Video circuitry OK.
Go to step 3.
3. Disconnect and carefully
inspect all four cables on
back of LCD panel for signs of
damage, corrosion, or pinched
wires.
Yes Replace damaged cable(s)
where needed, otherwise
reattach connectors. Retest.
X03
No Go to step 4.
4. Power ON computer and verify
if issue still occurs.
Yes If connections are secure and
display is still ickering, go to
step 5.
No Issue resolved.
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