This is solved. Turns out the WLED display driver chip was internally shorted to ground. That in turn blew the 2A fuse that fed the P channel FET that drives the power to the boost circuit. Replaced the LP8543 device and then the 2A fuse (tiny 0402 package) but still did not have a backlight. Started probing around and discovered that the enable pin for the LP8543 was low. They use a 300K / 100K resistor divider network to get the 3V enable. My 300K resistor was open. Replaced that and BOOM I have a backlight. And that missing device is a capacitor on the output of the boost. Considering the hours I put into this it hardly seems worth it but I rescued this board from the landfill anyways :-) Soooo there you have it.
You have one of the original 2006 Macbook Core Duo (i.e. NOT Core 2 Duo)? As far as I know the LCD panel itself is the same between 2006 to 2008. There are at least 3 makers of the screens (I think Samsung, LG, and someone else) but they are interchangeable. I buy new displays from a company in BC and I usually end up getting Samsung displays. The processs to change them is a bit involved... probably not for those who have never worked on Macbooks before.
Found it! Although I had examined and cleaned the top side of the logic board I had not done a complete job (slap wrist). I removed the logic board and there was corrosion on the bottom side of the power connector. I cleaned it up with IPA (Isopropyl Alcohol that is... not India Pale Ale since that is for internal cleaning :-) After cleaning, reassembled and everything is tickety boo. Note to self... never do a half job.
When it dims do you see the screen display the dimming logo (the one that hows the brightness sun logo and the bars decreasing below it? The reason I ask is if the key on the keyboard that controls brightness is "stuck" then it would continuously dim the display. You could verify by disconnecting the built in keyboard and using an external keyboard. Just a thought...
You can also reset your power management. Remove the battery and unplug the charger. Then hold down the power button for 5 to 10 seconds. This resets power information and might be related to your sleep issue. It is also possible that you have a bad battery/sleep cable assembly. This would give these symptoms as well.
I would recommend a great utility called iStat Menus. Version 2 is free. Version 3 costs. When you install this it gives you all sorts of info along the top of the screen but the one you are interested in is the temperature of your CPU. Sounds like you may be running hot. You can also add the fan RPM (revolutions per minute) to the display and this will tell you how fast your fans are spinning for a given temperature. Sounds like you want to blow out the dust from the heatsink (as already stated) and, if you are comfortable, remove the heatsink and reapply with new thermal interface material (TIM).
I find that the MBP fans default to only 1000 rpm until it gets insanely hot. First thing thing I would do (after blowing out the dust... well OK, the second thing :-) is to install iStat Menus (version 2 is free, version 3 costs). Then see what your actual temps are while running different tasks. iStat can also display your fan RPM's and you will see them both at 1000rpm. Next, install fan control. This is a great utility that can adjust the fan profile to something a little more agressive that will substantially reduce temps. Play around with it and find the right balance of temps and fan noise. It is very easy to use. Linked below. http://www.macupdate.com/info.php/id/231...-control At least at the end of these steps you will be able to tell exactly how hot your Macbook is getting. Cheers