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TSU Meeting MONDAY — May 5, 2025

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David Anderson, Jeff Burrell, Greg Harter, Ryan Gray, Adam Trionfo, Carl Miles, Rich J, James Martin, John Stroebel, Chris, Paul Holmgren

The Monday session opened with introductions from several new members — Chris (UK-raised, now Bay Area, started on a 16K ZX Spectrum and now a deep Sinclair/Timex/Eastern-European-clone collector), James Martin in Logan, Ohio (recently gifted a TS2068 in original packaging and nervous about powering it up), and John Stroebel from Minneapolis (long-time ZX81 user, Medtronic implantable-device engineer, and a collaborator with Paul Farrow on the EightyOne emulator's recent sound/speech updates). The group walked James through TS2068 power-supply safety: Sinclair/Timex bricks are center-negative (opposite of most modern adapters), so check polarity with a meter before plugging anything else in. They covered the 2068's switching regulator, the marginal 78L12 that runs the AY sound chip, and the recommendation to run modern regulated supplies at ~15 V to keep heat down; Rich offered James a spare brick. Display options were also covered — composite into a cheap multi-input LCD, or Jeff Burrell's PicoVideo board for VGA out.

Jeff Burrell did show-and-tell with the first prototype of his 2060 board — a modern recreation of Timex's never-shipped Bus Expansion Unit for the TS2068. The board bundles Pico-storage and Pico-video functionality and adds a slot for user-defined expansion boards; Jeff is mid-troubleshoot but said the PCB has been mostly clean. He gave background on the historical 2060 — long rumored, only weakly evidenced until Lon Hildreth's box of saved Timex documents surfaced a spec sheet — and traced the Burroughs-to-Timex talent pipeline (Luke Ailey, Scott McCork, Lon, Will Colum, Dave) that produced the 1500 ROM revisions and the cartridge support.

Greg Harter previewed the next version of his ZX81 Wordle, now being rebuilt in z88dk for multi-platform release (ZX81/TS1000, ZX Spectrum, TS2068, and a Chroma-color ZX81 build). To fit a >16 KB dictionary into 16 KB, he bit-packs each letter into 5 bits (8 letters per 5 bytes), uses binary search over the packed data, and encodes plural/-ed endings as alternate terminator codes so they can be filtered. Dictionary was built by grepping a Unix word list, stripping proper nouns, and hand-curating endings. He expects to release within a few weeks, in time for VCF Midwest.

Ryan Gray demoed his revived Load Runner-inspired game Thief (originally written in 1990). The breakthrough was applying the DEFADD trick — exploiting Sinclair BASIC's DEF FN system variable to do fast block memory copies — to blast pre-computed color attributes into screen memory, getting color into the game without dropping to machine code. He's added a level editor, joystick support, and emulator-friendly start-up; the remaining bottleneck is the level-scan for treasures. The group lined him up to demo at VCF Midwest (Chicago, second weekend of September), with Adam to design new levels. Other items: Carl Miles reported his enhanced TS1000 ("1068") prototype is now working — the culprit was a flaky Z80 (likely a bad M1) — and he'll cover it on Sunday May 18; Rich J described downgrading three of his TS2068 BASIC programs (hangman, scramble) to run on the TS1500 and building four ZX81NU clones that drop into TS1000/TS1500 cases. Distribution of Carl's TS1510 cartridge clones came up — plan is to sell them through David's site alongside Ryan's TAP-to-DCK converter and a downloadable library of pre-converted cartridge images. Next meeting: Sunday May 18 at 2 PM Eastern.

Highlights

  • Jeff Burrell unveiled the first prototype of his 2060 board — a modern take on Timex's never-shipped TS2068 Bus Expansion Unit, integrating Pico storage/video plus a user expansion slot.
  • Greg Harter previewed a multi-platform Wordle (ZX81/Spectrum/2068, plus Chroma color) built in z88dk with a 5-bit-per-letter packed dictionary >16 KB.
  • Ryan Gray demoed Thief, using the DEF FN / DEFADD trick to fast-copy color attribute data and add color to a BASIC game without machine code; targeted for VCF Midwest.
  • Carl Miles reported his enhanced TS1000 ("1068") prototype is finally working after isolating a faulty Z80 (suspect bad M1).
  • Plan agreed: distribute Carl's TS1510 cartridge clones via David's site, paired with the TAP-to-Cart converter and a download library of pre-converted cartridge images.

Projects discussed: TS1510 Cartridge Interface Clone · TAP-to-Cart — TS2068 Cartridge Conversion · TS-Pico · "1068" — Enhanced TS1000 · DEF FN & BASIC Technique Deep-Dives Topics: Hardware projects & new boards · TS2068 / TC2068 · TS1000 / ZX81 / TS1500 · BASIC programming · Prototypes & rarities · Pico / modern interfaces (UnoDos, etc.)

Summary generated from the meeting recording; the full transcript is kept in the group's private archive.