AX-990 Regulator Replacement

As I was testing the new switch on my second AX-990 (with the cover removed) I happened to touch the heatsink and was surprised to find it was very hot. It's a piece of hardware literally designed to absorb and re-radiate heat, so perhaps I shouldn't have been too shocked at this. But it was very hot — almost untouchably so. That got me thinking: is it possible to replace the linear regulators with a modern equivalent that emits less heat? After all less heat is better, right? And electricity turned into heat is basically wasted energy.

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AX-990 Switch Replacement

One problem that's been apparent on both my AX-990s was the incredibly poor video quality. Colours would be distorted and sometimes the TV would lose the video signal entirely. The culprit is the toggle switch on the rear that changes between MSX and Sega modes. Often just touching it lightly was enough to make the video signal dance and flicker. With only a small amount of work this can be fixed and perfect composite video is the result!

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Sakhr AX-990

The AX-990 was an MSX1 computer released around 1992 for the Arabic market under the Sakhr brand by the Al-Alamiah company. It was a dual-mode machine: both an MSX1 home computer and a Sega Mega Drive games console. The two modes could be switched between using a push button on the rear of the case.

The two halves of the machine were not capable of interacting with each other (as in the Sega Teradrive). The power supply, composite video encoder, and joypad/joystick ports were shared; while the MSX and Mega Drive circuits were switched on and off as required.

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First Post

Going to give this blogging thing a go again.