This shows the removable top with the heatsinks, and power resistors mounted underneath. I ran out of room inside the enclosure, and also felt better if the major heat source was somewhat removed from the electronics inside. I mounted it on top because the heatsinks fit better there. There are several holes drilled in the top, to allow the forced air from the muffin fan to escape underneath the resistors, thereby providing additional cooling. The plug is partially shown on the right. I can leave the top in place, and simply plug in a light bulb(s) instead, if desired. A couple of left over resistors and capacitor are on the right. This type of capacitor has four values in one "can" ; 4, 20, 100, and 120 Mfd. The 4, 20, and 120 are rated at 450 volts. The 100 Mfd is rated at 150 volts. All have substantial safety margin over the 78 volt peak from the 56 volt transformers.
This looks like a real mess, but I really do have a wiring diagram around here someplace . . . . . Actually everything fits OK, and the muffin fan would probably not be required. I have noticed a moderate warming of the discharge capacitors, when running for a long time with two values from each selected. This will probably not be the case normally. At most, only one value, or one from each will be needed. Power is brought into the box via a connector from an old computer (male plug on the input side) It was available from the scrap box, and was easy to install. I used pieces of Aluminum angle to join the front and sides. They do not go all the way to the top, allowing the 1/4" thick top with the heatsinks to just recess into the box. The two large transformers are 56 volts, wired in parallel to increase the output current. The small one is 12 volts for the electronics and stepper motor. I have two 2,200 Mfd, 300 volt caps in parallel before the load resistors, for a pretty good "reservoir". I used 14 ga wire for all of the spark power circuits.
