Randomvariations

4/8MB 72-pin SIMM adapter I recently purchased a ROM 01 Apple IIgs with the intention of using it to further my disk image explorations. While it came with an Apple 1MB expansion card, I quickly realized that it would be useful to have more memory install

Assembly of the OSI-300 Mini is fairly straightforward. I typically start with the shortest height parts, and work up to the tallest. 1N4148/1N914 diodes D1-D20, D41, D42, and D43 The black bar on each diode matches the bar on the silkscreen. 220 ohm resi

As part of my project to run Zork on the Tandy WP-2, I found it useful to dump the ROM and take a peek at what it was doing. While the Service Manual (available online from Club 100, the Internet Archive, and other places) contains a wealth of information

Z80 Membership Card (Front) While at VCFMW last year, I spent some time talking with Lee Hart about his ELF Membership Card. He showed me a new project that he had been working on with some others called the Z80 Membership Card. Z80 Membership Card (Back)

The final tally of parts is: 1x R6502 NMOS 6502 CPU 1x 6264 8k x 8 SRAM 4x 7417 Hex Open Collector Buffer 1x 7402 Quad NOR Gate 21x 3mm red LED 23x 1N914/1N4148 diode 1x 1N4001 diode 1x 100 ohm 1/4W resistor 34x 220 ohm 1/4W resistor (I used 1/8W) 1x 2.2k

Switches with logos Switch backs While working on my mini OSI-300 Trainer, I encountered issues with the switches that I had purchased. The seller advertised them as SS12D07 switches, which according to the data sheets that I had found, were non-shorting,

As indicated in my previous posting, I had issues with the switches that I purchased and their usage in the OSI-300 mini. I took apart one of the switches in order to get a closer look at how it worked and if the switch could be adjusted to work properly

Prototype mini-trainer I recently received the boards I designed from the manufacturer. They were very well done, even with the tight tolerances required to line up the various components. Additionally, the parts I ordered to assemble the board arrived as

After playing with Kicad, and particularly with pcbnew, I have worked out a PCB design for a "mini" version of the OSI-300 trainer. Only a few changes have been made to the original design. The primary adjustment is to swap a 6264 SRAM for the original 12