update 2021/02/15: Added pictures of a Rev B power supply
The Atari Jaguar has no protection against reversed polarity power supplies, so if a center-positive PSU is mistakenly connected it will destroy several components in the console rendering it dead*. It is common knowledge that you can add a diode to protect against this, but I searched for proper instructions without luck. ElectronAsh was kind enough to guide me through the fix, which I detail below. I have a guide for the Jaguar CD as well.
If you are already inside a Jaguar doing other work like a recap, you might as well add the diode because it only takes a minute to install. Once complete, your Jag is protected, but you should still avoid connecting a center-positive PSU.
1 Rectifier Diode – 1N5400 (protection up to 3A) – you can also use a higher voltage rated diode
1. Desolder the wire that connects a ferrite filter to the positive pin on the side of power supply terminal. Some Jaguar revisions have different wire colors, so the wire may be be black, red, or white. Pay close attention to the location of the wire in the photo above, not its color!
2. Solder a diode to the (now empty) trace where the filter wire connected. The bar or line on your diode denoting the cathode (negative) side should face up and the anode (positive) side should be soldered to the PCB.
3. Solder the filter wire to the cathode side of the diode with the bar. Clean any flux left on the PCB with isopropyl alcohol. You’re done.
*If your system was killed due to a positive-center PSU, you’ll need to replace a power regulator, the two caps near it which likely exploded, and a nearby resistor that probably caught on fire.
– If you solder the diode backwards, the console won’t power on.
– Do not attempt this modification without a complete and total understanding of what you are doing. RetroRGB is not responsible for any consequences of your mistakes.
– While you have the Jag open, consider replacing cap C150 (2200uF 16V), which causes a common screeching sound when it goes bad.