Beta Disk 128X:
Beta Disk 128X is a controller for 1 to 4 floppy disk drives for ZX Spectrum, ZX Nucleon and compatible computers. It comes from the original interface of the same name from British company named Technology Research Ltd, with which it is fully compatible. The design is virtually unchanged from the original wiring, with just a few changes, the description of which will go further. This ensures compatibility with the original interface. "128" in the interface name indicates that it is a version of the ZX Spectrum operating with both 48KB and 128KB RAM. "X" indicates ZX Nucleon 512KB compatibity.
• Optional to connect 1 to 4 floppy drives 3.5" or 5.25"
• Fully compatible with the ZX Nucleon 512KB, ZX Spectrum 48KB, 128KB "toast rack" and 128K +2 Amstrad gray box. It is also compatible with other ZX Spectrum clones with a standard system connector and ROM compatible with ZX Spectrum 48KB or 128KB, for example Didaktik M. Didaktik Gama can be connected after additional fixing, see next description. Interface is incompatible with the ZX Spectrum +2A, +2B and +3, these have non-standard signals ROMCS (2x) on the edge connector and incompatible ROM.
• The device is realized on two printed circuit boards vertically connected by connectors
• Fully through bus on the bottom board
• Used original FDC1793 floppy disk controller or analog
• Integrated voltage converter from +5V to +12V for controller FDC1793
• Four different versions of the system TR-DOS selectable by switches, 5.03, 5.04T, 5.041 and 5.05cz (5.04T and 5.041 contains TURBO Format of diskettes)
• LED power-on indication (green LED) and TR-DOS system activation (red LED)
• Board is powered by external source 7,5-9V/300mA max. via the rounded DC power source connector 3,5/1,4mm (positive pole center)
Because the schematic is largely taken from the original interface, is directly compatible with these computers without any further modifications:
• ZX Nucleon 512KB
• ZX Spectrum 48KB
• ZX Spectrum 128KB "toast rack" with radiator to the right
• ZX Spectrum 128KB +2 Amstrad gray box
• Didaktik M
Compatibility depends on whether your computer is equipped with a system connector with a standard distribution of the appropriate signals, which the Beta Disk 128C interface uses.
ZX Spectrum 128KB +2A, +2B and +3: This computers is incompatible in terms of the ROMCS signal (25B), which is doubled with them. In addition, they also contain incompatible BASIC ROM. Therefore, the Beta Disk 128C interface can not be used with them!
Didaktik Gama 80KB, 192KB: Didaktik Gama computers of all versions meets the compatibility of the system connector, but they have an internal 8255A parallel interface using the same port addresses (31, 63, 95, 127), as Beta Disk controller, you can not use this computer without any modifications with the Beta Disk! Otherwise, there will be a collision of the 8255A parallel interface with the controller 1793 on the bus, and they could be damaged!