Thiseldo

Blog

  • QM2000 ROMs

    I’m looking at getting this QM2000 up and running and as a software task, dissasembly of the ROMs is the fist stage. Looking around, the ROM images don’t appear to exist on-line due to the QM2000 being a rare beast. The EPROMs on the GM813 Z80 board and the GM812 Intelligent Video Controller were dumped. Using Claude-Code to perform analysis on the disassembled code, it was able to produce a comprehensive description when combined with the available hardware and software documentation available for the boards. Existing versions of the monitor code were compared to verify the disassembly and analysis was correct.

    The monitor ROM for the GM813 was found to be an early version of the SIMON Monitor specifically coded to use the GM829 Disk controller.

    The output from the disassembly is available in my QM2000 Github repository.

  • QM2000 Power Supply

    It needed a little bit of dismantling to get to the power supply and upon opening it up, first impression was that it looked ok. On closer inspection a number of the capacitors were in need of replacement. New capacitors are on order.

    The main power switch was replaced and a new VDU socket was added as I didn’t have a plug for the original.

    Power switch and VDU socket
    Replacement power switch and updated VDU socket.
    PSU voltages
    Capacitor looking like it had seen better days.

  • Apple II Europlus

    After a retro computer event run by NADHack in 2025, I was approached and asked if I would be interested in an old Apple II computer. After a quick inspection, a deal was done. I acquired an Apple II Europlus, which is the European market version of the Apple II Plus. This example was made in Ireland in 1979, according to labels inside and on the case. The system arrived in a pair of what can only be described as custom made, foam lined carrying cases. One case for the base unit and floppy drives, the second for the monitor. The monitor is not an Apple branded monitor. Also included were a number books and a collection of 5 1/4″ floppy disks.

    Apple II with twin disk drives

    The power supply was re-capped, especially the RIFA capacitor which was showing signs of degrading. After this it was powered up and found to be mostly working. The keyboard had problems that were not resolved by cleaning and it looks like the keyboard encoder chip is no longer working correctly.

    I was able, with careful typing to be able to boot one of the many floppy disks that was included.

    A HDMI video card was purchased rather than trying to feed the existing video out into a suitable convertor.

    The keyboard encoder fix is still a work-in-progress.

  • Quantum QM2000

    I recently acquired a Quantum Computers QM2000 at a local auction. Having never seen one before I was interested to see what it was like. It was listed as not working due to having failed a PAT test and therefore the power leads were not included. One of the few sites I found showing the computer in magazine advert from 1983 They QM2000 is based on the Nascom-2 bus with cards made by and sold under the Gemini name. There is some limited information on the QM2000, but more information and schematics for the Gemini cards. At this time it has not been powered up as it would need the mains electrical sockets replacing and the Power supply capacitors replacing.

    Triple floppy drives, which are unusual
    Original Green CRT monitor
    Original green CRT monitor
    Chunky keyboard with missing keycap

    It has a selection of connectors on the rear that connect to various peripherals.

    Rear connectors: Power in, Monitor Power, keyboard, RS232, Centronics, Video, Cassette and lightpen.

    Inside of the QM2000.

    Lots of space inside
    Rear connectors form the inside
    Inside of monitor

    The main boards can be removed.

    GM813 Z80 CPU and 64K RAM card
    GM812 Intelligent Video Controller (IVC)
    GM829 Disk controller card