I'm working on a headless iMac G3, but I'm having a problem with the video out. The output is very fuzzy (both on a CRT and LCD) and has purple streaks coming off of images going towards the left side of the screen. I read here that this problem could possibly be the lack of -10v to the video card. This makes sense to me as as far as I've heard, there is a significant difference in the motherboard layout of the 500MHz and above SL iMacs. My question is, how do I get -10v? The forum posting I saw said to use 2 or 3 diodes, but I don't understand how I could pull that off. A couple of people I asked said to just use a resistor. Thanks.

Okay, so you need to pick up that uA79L10 OR get the correct diodes. The correct diode(s) will downstep the current much like a resistor will. You can use a resistor, though you don't need gate control plus the diodes job is to only allow current to flow in one direction, so it would be pointless.

The diode will knock down the -12V enough so that it's actually a -10V connection by the time it reaches your video card.

If you want to make sure this will actually work, get an older ATX power supply from another computer and use the -12V connection from that power supply. Once you have that, add the diodes to that -12V and then connect it into you video cable harness. That won't make you mess up your existing cable and will actually provide the power to your card and act as a less messy way of testing if that was the culprit.

Ok, so I need to find a diode with a 2 volt voltage drop. What would be the harm of supplying the -10v? The original harness supplies the -10v, so if it's supplied an it's not needed, no matter.

Got it. Adding 5 IN4006 diodes in series to the -12v line dropped it down to -9.9 volts. Cleared up the video problem.

That's awesome! Glad to see you got it all fixed up. What are your plans with the machine now?