Q: The bottom half of my display is dimmer than the top. Are the displays back lit with florescent lights?
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Jul 18, 2015 1:59 AMby K Shaffer,Depending on the build model series and sales identifier information for the year of manufacture
there could be one of a few different technologies involved in the display backlight and support
circuitry behind the display as well as inside the main computer, that may affect output visually.
Even an LCD with LED backlight may have a partial failure. Liquid crystal units with backlight cool
fluorescent may exhibits certain patterns that differ from those of failed 'light emitting diode' backlight.
By what you've mentioned, per visual effect, you may be in for a service interval at an AASP.
To identify your computing product would be helpful in order to proceed.
• How to identify iMac models - Apple Support
In any event...
Good luck & happy computing!
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Jul 18, 2015 10:10 AMby K Shaffer,HelpfulFrom what the iFixit repair guide shows for the intel-based iMac of that series, there
are three groups, yours appears to be second one, in this section:
https://www.ifixit.com/Device/iMac_Intel_20%22_EMC_2133_and_2210
Once the cause of the symptom you observe is determined by testing & troubleshooting
there are a few different sections of the repair guide to include accessing the Display.
There are other parts of the guide, for your model, that have parts that affect the display.
This only shows front access where the glass can be removed, to access & replace the panel, etc.
While this similar guide section suggests when replacing a hard drive, to just move the panel:
https://www.ifixit.com/Guide/iMac+Intel+20-Inch+EMC+2133+and+2210+Display+Panel+ Replacement/998
Removing CCFL from iMac 20-inch LCD CCFL assembly:
{The CCFL are soldered to the wires so not a simple plug in replacement}
https://www.ifixit.com/Guide/Removing+CCFL+from+iMac+20in+LCD+CCFL+assembly/5865
There are circuitry components which support the function of the display, on/near the logic board, that
may act up and could be the cause of some symptoms. They should not mimmick a partial backlight failure.
However when actually troubleshooting, some methods may invite inspection or testing to a greater degree
to sort out these kinds of other items which may (or may not) be a problem unto themselves.
The power supply for LCD panel, the cabling to the panel for data, and other bits should be inspected
and may be suspect. Either before you actually begin a repair, or once you've accessed the interior.
A weak cable may break, or not be capable of withstanding anything but the kindest handling.
Hopefully you can either do the troubleshooting to isolate the exact cause, or find a suitable mechanic
with the necessary familiarity with skills, tools, and correct replacement parts to perform the task(s).
Good luck & happy computing!
