This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
Okay; here is your very own A2-2000 On-Line Power Supply Mods Kit! Swapping-in fat leads is, technically speaking, a pretty simple job. You pop out the power supply, open it, unsolder old +5, +12, and Ground leads, solder in the new leads, close and replace the power supply. The tricky part is what hackers call the "mechanics". First, #12 or #14 gauge wire is not very flexible. Getting stranded wire (instead of solid) helps. Probably, #14 gauge is more than fat enough for all three leads. One case where #12 or #10 gauge may be worth the extra trouble is the +5V lead. Use wires colored the same as those you replace. On the standard connector, the first two leads are Ground. Almost always, these are black. Next, there is a space, then, in order +5, +12, -12, -5. Depending on the bother involved, you can unwedge the wire bundle where it passes through the supply case and remove the three old wires (+5V, +12V, and one Ground wire). Or, you can just cut away each old lead. Leave the -5V and - 12V leads and one Ground lead alone. Getting to the PS circuit board involves some work. After removing the mounting bolts, you will have to scooch up the board in order to get to the bottom side. This will be easier if the wire bundle has been unwedged. Another hurdle is soldering to the circuit board. Once the old leads and excess solder are removed, you will probably find that the holes are too small! A jeweler's screwdriver makes a good hand drill for enlarging holes. (Drill from the circuit side. Be careful not to tear or dislodge the printed circuit.) The new leads should be routed through the unused fan slots. (If a fan is attached, remove it. It's in the wrong place to do much good in cooling your GS.) Note: If you have a fan mounted to the PS and you wish to keep it, then, it will be necessary to enlarge the original cable exit hole. A sheet metal "munching" tool should let you do this without having to entirely remove the PS circuit board. (Just be sure to catch all of the munched pieces!) When routing the leads be careful not to place a twisting force on a lead where it is soldered to the circuit board. To get to each spronger (contact) in the plug, press on it through the slot on the side near the wire end. This pushes up a small retaining tab so that pulling on the attached lead will pull out the spronger. Cut off the old lead, clean the end, and solder on the new lead. Press the spronger back into the plug. To avoid mixups, it's best to complete the process for each lead before doing the next. When plugging in the power supply, take time to shape and arrange the wires to minimize stress on the motherboard. Motherboard Mod Fatter +5, +12, and Ground leads should protect you power supply and reduce circuit noise. If audio noise in your stereo card output and/or system bombing due to noise glitches were problems, they may be eliminated. A lot depends upon which cards you've installed, which slots they are in, and whether your IIgs is a ROM-01 or ROM-03. The motherboard circuit traces supplying power to each Slot are fairly skimpy, especially on ROM-01 boards. A heavy power user in Slot 7 can produce significant noise up and down the entire Slot 'backplane'. The cure is to remove the motherboard and run leads to a couple Slots ... First, flip over the motherboard and get oriented. Below is a quickie sketch showing the Power Connector points as well as key power pins for a Slot. The view is from the Bottom with the Back of the motherboard facing you: Bottom of MotherboardPower Connector Socket Slot X GND +12V (pin 50) X X (pin 1) X GND X X . X +5V . X +12V . X -12V X -5V X X GND (pin 26) X X (pin 25) +5V.... Ground Plane Area (plug shields, etc. connected here) .... | |______________ Back Edge of Motherboard _________________________ A good way to make sure you know what's where is to use an Ohm meter to check Resistance from pin 26 (GND) to a metal plug shield near the back of the motherboard. (Set your meter to Ohms X1. Touch one meter lead to pin 26 and the other to a metal plug shield. Resistance should read nearly zero. Reverse the leads and repeat the check. Again, Resistance should read nearly zero.) Repeat the check for R between pin 26 and the GND points on the Power Connector socket. R should be nearly zero. Using a marker pen or white-out, mark pin 26 (GND) on Slots 3 and 7. Also mark the GND points of the Power Connector socket. GND: On the bottom side of the motherboard, connect a Black #16 gauge wire from one of the Ground points of the Power Connector socket to the Ground plane area near the back of the motherboard. Run a short Black #16 gauge wire from pin 26 of Slot 3 to the Ground plane; run a short Black #16 gauge wire from pin 26 of Slot 7 to the Ground plane. (You may need to scrape through green insulating lacquer to solder to the Ground plane area.) +5V: On the bottom side of the motherboard, connect two #16 gauge Red wires to the +5V point of the Power Connector socket. Connect the other end of one +5V Red wire to pin 25 of Slot 3; connect the other end of the second +5V Red wire to pin 25 of Slot 7. +12V: If you have any cards which are likely to draw heavily on the +12V line, then, on the bottom side of the motherboard, run a #18 gauge White wire from the +12V point of the Power Connector socket to pin 50 of the Slot in which the card is normally located. Otherwise, just run an #18 gauge White wire from the +12V point of the Power Connector socket to pin 50 of Slot 7. Check your connections. One quick check is that the GND and +5V wiring to Slots 3 and 7 should be Black, Red (moving left to right) and Slots 3 and 7 should 'look the same'. Any +12V wire should be on the same side of the Slot (i.e. the same column of pins) as GND. None of the wires should be connected to a middle pin on any Slot. Notes: 1. All wires are insulated. 2. When cutting wires, allow enough slack to permit routing each wire. You want to avoid having a wire rest against pointy connections on the motherboard. Route wires away from motherboard mounting holes and around places where the bottom of the case supports the motherboard. 3. The case's bottom and back metal shields are something of a shorting hazard. Replacing the motherboard is much easier if these shields are popped out and ditched. Once everything checks out, replace the motherboard taking care that no wires are caught between a support point and the motherboard.