I'm writing this using a recently repaired Gateway 900g. You may be correct about the power supply, as that was the problem on this unit. There was absolutely no response with this unit. No blue LED, no dim display. Nothing.
WARNING: BE SURE TO UNPLUG THE AC LINE CORD. THE POWER SUPPLY HAS DANGEROUS 120 VAC PRESENT IF LEFT PLUGGED IN. If you don't know what you're doing, it's best not to attempt a repair!!!
is a bit tricky, and there's a variety of different sized screws used; so keep track as you go. First you remove the front bezel (be careful as the two control boards on the lower right need to be disconnected). There are two screws (lower left and lower right) that secure the shell, the rest of the frame is just a snap fit around the perimeter.
Then remove the 6 screws that hold the LCD frame to the rear plastic shell. Careful here as well, as you must disconnect the back light cables AND the signal cable to separate the LCD from the Power Supply / Signal Processing board.
The Power Supply board mates to the Signal Processing board thru
a 2x5 pin header. This contains convenient points to check the +12V and +5V supplies. In my case the +12V was OK, but the +5V was reading about +2.5V...not good! THIS IS REALLY DANGEROUS TO CHECK AS THE 120VAC IS ONLY AN INCH AWAY.
Here was the key symptom on my unit. Your's may not be the same. If I disconnect the Power Supply from the Signal Processing board, then the +12V and +5V read correctly (as well as the +16V that goes to the Backlight
However, once I connect the Signal Processing board, the +5V drops to +2.5V. However, the Signal Processing board seems to run correctly off of an external supply drawing about 300mA.
On closer inspection of the Power Supply board, I notice that 4 capacitors had buldging
tops (domed). This indicated some stress. These were capacitors C205, C206 (470uF/25V) in the +16V section; and C210 (470uF/25V) and C209 (220uF/25V) both in the +5V section. I didn't have a Capacitance
Meter handy, so it was simpler to just replace all four parts with similar values. (There's a lot of latitude in making these substitutions.) But be sure you have voltages a *least* greated than those needed; i.e. 16V or 5V. They used 25V to have plenty of headroom.
After replacing the 4 Capacitors, the Voltages and Blue LED responded normally. After reconnecting to the LCD assembly, all was well. Reverse the disassembly
process, and you are ready to go.