Now, how difficult is it to replace/repair/work around. Are the components available at my local ham electronics dealer?
The components you need to buy are two resistors (or a trimpot), but the trouble is identifying where to put them and how to disable whatever is performing the function in-circuit right now. The temp compensation may be integrated onto the LCD, or found on the inverter board, or found further away in the power supply. Reverse-engineering the product enough to do this hack is not a simple task. First step would be to obtain the datasheet for the LCD, if possible. You can work back from the Vee pin on the LCD through whatever drives it, and determine where to disconnect the old circuit and install your new one. If the datasheet can't be found, then scoping the LCD connector for a signal around -18 to -21V will probably identify it. Sometimes there is a -30V rail from the PSU (or a small switchmode power supply on the backlight inverter board) run through a digital pot, sometimes it's a purely analog circuit with a thermistor, sometimes there is a dedicated Vee supply IC with programmable voltage control... there are no simple heuristics I can offer, I'm afraid.
However, before attempting to troubleshoot this further, you should disconnect any external monitor, reset PRAM and boot off a MacOS CD. Leave the unit a couple of hours. If there are no problems, then you have a software issue. This isn't very likely but it should be investigated before trying a complex repair.
-- Lewin A.R.W. Edwards http://www.zws.com/ Learn how to build high-performance embedded systems on a budget! http://www.amazon.com/exec/obidos/ASIN/0750676094/zws-20
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