I got a non-working Amiga 600 from the UK. The computer looked to be in good physical condition, it included the mouse, power supply and some other cables. However the computer was listed as broken, it seemed to be one of those very frequent cases of "it was working years ago when I put it in storage, but it is not working now."

Amiga-600 in very nice condition. The keyboard shows initial signs of yellowing.

Repair

The most common problem with non-working Amiga 600 is capacitor failure. The SMD electrolytic capacitors used in 1990's electronics usually fail after near 30-years, and when they fail, they often leak corrosive fluid that destroys the motherboard by slowly corroding traces and even getting into integrated circuits and other components.

While I did not see signs of capacitor leakage in the motherboard, I proceeded to replace the SMD electrolytic capacitors.

Extreme care is necessary to remove these capacitor, because it is easy to lift pads and traces from the board. The best technique is to use hot-air to melt both terminals of the capacitor, then carefully lift it with tweezers. Another technique, that is faster but riskier, is to horizontally twist the capacitor with long nose pliers, avoiding puling on it, until it breaks, leaving behind its terminals still attached to the board. The terminals can then be easily removed one at a time.

Replacement thru hole capacitors on the left of the board.

I did not have SMD electrolytic capacitor in my parts bin, so I used thru hole capacitors modified with some wire origami to match the SMD pads. This is a temporary measure while I wait for proper replacements to arrive in the mail.

Example of wire origami for fitting a thru hole capacitor to SMD pads.

My plan was replacing capacitors a few at a time, stopping in between to test the computer.

After replacing the first batch, C612, C303, C304, on the left side, the computer came to live. I believe that capacitor C612, which is used in the reset circuit, was preventing the CPU from starting. There was also some leakage under it that I promptly cleaned with a Q-tip soaked with white vinegar (to neutralize the caustic liquid) and then with 91% Alcohol to clean the vinegar residue.

Microscope view of capacitor fluid visible after removing C612.

At this point, I stopped recapping with thru hole capacitors until the proper SMD capacitors arrive. There is no point in stressing the motherboard twice. These thru hole capacitors are not mechanically stable and may rip the pads if something bumps into them.

It is alive!

Keyboard Retrobrighting

While the computer was in very good conditions some keys were starting to yellow. I bleached those keys by sous-viding then in a plastic bag with regular Oxygen Peroxide (3%) at 70C (160F) degrees immersed in water. After a few hours, the keys looked much better. It is necessary to monitor this process to prevent over bleaching.

Contrary to what is often suggested, the retrobrighting process does not reverse plastic yellowing, it only bleaches it, and does not, in general, restore the exact original color. Still, it can make the computer look much better.

Floppy Emulator

Floppies are expensive and hard to find these days. I usually replace floppy drives with a floppy emulator such as the Gotek. Floppy emulators allow you to use a flash drive containing floppy image files directly in your old computer. Flash drives are so cheap and large that they can easily store all the software ever made for most old computers. The Gotek emulator is the most popular one and it is cheap, around 20 dollars for a basic model. I recommend flashing it with Keirf's FlashFloppy firmware that adds support for many more old computer image formats, and can be improved with hardware mods such as an OLED display, rotary buttons, speakers, etc. I like adding the OLED display, as it makes it easier to browse the floppy image files. Some folks sell modified versions of the Gotek hardware already flashed and with hardware mods. These sell for more than 40 dollars/euros depending on the vendor and hardware mods.

Homemade Gotek

A long time ago, I bought 2 Goteks that I modded and installed in my Amiga-500 and Atari 1040ST. Then I realized that I was going to need many more for all my old computers. I love open source hardware that I can assemble myself. So I looked for open source alternatives, and I saw that some enthusiasts had created versions of the Gotek PCB and had made designs freely available. The variant designed by Sundby is particularly nice: its size is under 100mm x 100mm meaning that it costs about 1 dollar per PCB to be professionally made; it adds support for 3-inch floppy connectors, as used in Amstrad computers; its mounting holes match the original Gotek; and it directly supports the OLED display, rotary button, and piezzo speaker mods. Furthermore, Sundby made his design available in EasyEDA.com so that it can be easily modified. When I first tried to order PCBs, some trace spacings violated manufacturing constraints of my PCB vendor, making it much more expensive to fabricate (over 20 dollars, instead of 5 for a batch of 5 PCBs). Thanks to Sundby's open design, I easily rerouted the PCB to correct the problem.

If you are looking for a nice Gotek, consider buying directly from Sundby's website.

I used one of those PCBs to assemble a Gotek for the Amiga-600.

My version of Sundby's Enhanced Gotek. I rerouted the board to make it cheaper to manufacture. I am using some thru hole components (2 capacitors, crystal, and USB socket) instead of SMD to use parts I already had.

To mount the Gotek in the Amiga-600, I 3D printed a bracket and a display housing, both designed by CrazyBob and available on Thingiverse.