C64 Light Scanner
2 April 2025
Commodore 128 black screen
24 April 2025
I find myself in front of this very unusual and almost unknown computer.
The Mattel Aquarius was designed by a company called Radofin, based in Hong Kong, and marketed by Mattel, the company famous for Barbie and the Intellivision consoles. They too wanted to break into the growing home computer market, which at the time was dominated by Commodore, Sinclair and others.
Launched in 1983, the computer is compact, with a membrane keyboard like the ZX Spectrum but with 4KB of RAM and a Z80 processor.
Its graphics couldn’t compete with others in the same market. It also had no joystick ports and could only be used with a dedicated expansion that allowed two pads to be connected. The result? A big FLOP!
This repair starts well but ends badly, why? Look at the problem on screen: the signal is there, the computer responds to commands, but there are strange squares on the screen. At first I thought of a problem with a RAM bank, and now let’s see how it went.
Here are the two RAM banks removed and under test.
Unfortunately we need to open a parenthesis here: faulty chips don’t always have a fault so serious that it always shows up. There are memory chips that go short circuit and others that don’t hold data; these are easily spotted by any tester. Unfortunately there are faults that only show up under certain conditions, such as read speed or resistance on the data pins. In my case I found a RAM chip that passed the tests perfectly but in the circuit couldn’t drive the shared output on the bus. This problem led me astray, because I immediately took the memory to be good and carried on with the other chips, like the RGB encoder, the video processor etc..
The result? Everything good and a huge amount of time wasted!
The Glitch Solution
Find out how I solved the problem
I decided to write this article not so much for the repair itself, but to stop others falling into the same trap. To be sure a component is good, you need to test it on another machine too, or try fitting a known-good component in the one you are testing; testers are a great help but they can’t test everything 100%
