Replacing the Caps
Your Aquarius computer was probably manufactured between 1982 and 1983, so best-case scenario, the electrolytic capacitors inside are about 35 years old. Replacement ("re-capping") is a good way to ensure the non-replaceable components in your Aquarius don't get damaged from failing electrolytic capacitors.
I got back into the retro computers of my youth in the Summer of 2018, working first with Commodore 64 computers, and then the Aquarius (my first personal computer). In nearly every forum, collectors recommend replacing electrolytic capacitors that are over 30 years old, as is the case with the Aquarius. Due to the analog nature of the power circuitry of the Aquarius, the board-level voltages of +5v, +12v, and -12v are created through a collection of about 16 components, five of which are electrolytic capacitors, and two of which have "oddball" ratings that are rarely used in the modern world of switched power.
This kit is available from ArcadeShopper.com.
1 @ 10000uF - 16v, AXIAL
1 @ 1000uF - 25v, RADIAL
3 @ 10uF - 25v RADIAL (one of these three capacitors is rated at 16v, but for simplicity I've spec'd them at 25v... it's okay to use a capacitor with higher voltage, but don't change the capacitance)
1 @ 2.2uF - 50v, RADIAL
1 @ 1uF - 50v, RADIAL
1 @ 47uF - 10v, RADIAL
You'll also need the usual soldering/de-soldering supplies and tools
Below are the steps to replacement of the capacitors in video format:
1. motherboard removal
First, you have to remove the Aquarius motherboard from it's case.
2. RF Shield removal
Next, you need to remove the RF shield that encases the motherboard.
3. replacing the capacitors
Finally, you have to replace the electrolytic capacitors.
I don't go through re-assembly or testing, but, you know, duh.
optional: removing the power regulator
While you're at it, you can remove the 7805 power regulator so it can be replaced with a modern switching equivalent.
The first half of this video is removal of the RF modulator, which is not necessary for the re-cap process.
optional: replacing the power regulator
Second half of the optional process of replacing the 7805 power regulator with an OKI-78SR-5/1.5-W36H-C switching regulator.