Video upgrades (composite, RGB, HDMI)
Video output and upgrades — composite, RGB, S-video, VGA, HDMI mods, monitors, PAL/NTSC issues.
143 threads · 1339 messages · 2002-08-05 → 2026-04-29
The TS2068's video output has been the group's longest-running engineering frustration, and the diagnosis is the same in both eras: the on-die switching power supply that feeds the SCLD injects pulses into the +5V rail, smearing the composite picture. Vsevolod posted the canonical Yahoo-era fix in 2009 — disconnect the jumper to U3 pin 43 and drive it from a dedicated 7805 — and that same recipe (now usually with an R-78E5 buck regulator drop-in, per David Anderson's blog/YouTube write-up) is exactly what newcomers are still being walked through on groups.io in 2022–2023. The audio hiss is a sibling problem from the same shared-die layout, not the AY chip.
BRIGHT preservation is the other thread that spans both eras. Yahoo-era posters noted that the US TS2068 throws BRIGHT away on its RGB pads — unlike the Portuguese TC2068, which exposes full RGBI on the edge connector — and that BRIGHT on the TS even mis-affects black (visible in Manic Miner / Jet Set Willy). A 2021 groups.io Zoom-meeting thread between Eduardo Fuentes, Richard Atkinson, and David Anderson nailed down the theory (TS2068's Y signal differs from the Spectrum's, BRIGHT is multiplicative on Spectrum but additive/quirky on TS), and concluded the cleanest path is YUV→RGB conversion rather than tapping the SCLD's lossy RGB outs. That insight produced two concrete builds: the adapted tms-rgb.com YUV→RGB board (originally for TI VDPs, which share YUV out with the SCLD) and David's Pera-Putnik-based YUV→RGB PCB driving a Sega Genesis HDMI converter — both preserve BRIGHT through HDMI.
The modern era added two paths the Yahoo group never had. Jeff Burrell's FPGA video-upgrade board (2021–22) snoops the expansion connector, mirrors writes to video RAM into FPGA memory, and outputs VGA — and grew into a broader board concept hosting AROS/LROS-compliant boot ROMs and even CP/M-3. In parallel, Alvaro Lopes at the Load ZX Museum reverse-engineered the SCLD onto a Xilinx CPLD as a drop-in replacement (announced 2023), with Claudius cataloguing the three SCLD variants (TS2068 PAL, TS2000, TC2068) and explaining why only the Portuguese parts expose Intensity — work that's foundational for any future clone or repair.
For analog completeness, the 2009 NTSC Spectrum thread remains the reference for PAL/NTSC mechanics on Timex-Portugal hardware (Paulo Leite documented the TC2068 jumpers and 14.112 MHz crystal swap for 60 Hz), and Luis Antoniosi's 2015 S-video driver amp showed a middle-ground option before the modern era converged on RGB/HDMI. Across two decades the recipe has been remarkably stable: fix the SCLD's power first, then pick a video path — composite, S-video, RGB+HDMI, YUV→RGB+HDMI, or FPGA VGA — that fits the user's tolerance for soldering.
Key threads
- Video Blurry; was: TS 2068 - Sound/Hissing Problem (archive.org) — Yahoo-era root-cause diagnosis (2008–09): Vsevolod traces the noisy composite to switching pulses on +5V from the SCLD's on-die supply and posts the original 7805-on-U3 fix that the group still recommends today.
- NTSC Spectrum (archive.org) — Yahoo-era reference for PAL/NTSC mechanics: Paulo Leite documents the TC2068's jumpers and 14.112 MHz crystal swap for 60 Hz operation, with Portuguese-vs-US SCLD differences.
- S-video on TS2068 / Twister w/ ROM (archive.org) — Yahoo-era practical S-video driver amp by Luis Antoniosi (2015) — a middle ground between composite and full RGB that the group experimented with before HDMI converters became common.
- Topics for Next Timex Sinclair Zoom Meeting (End-of-July?) (#242 on groups.io) — groups.io 2021 deep-dive between Eduardo Fuentes, Richard Atkinson, and David Anderson on why preserving BRIGHT requires YUV→RGB conversion, with the Spectrum-vs-TS2068 Y-signal math that grounds later builds.
- Potential full color video solution (#386 on groups.io) — David Anderson surfaces tms-rgb.com (originally a TI VDP YUV→RGB board) as a candidate for the TS2068's SCLD YUV outputs — the first concrete modern path to RGB+BRIGHT.
- Video Upgrade Board for TS2068 (#306 on groups.io) — Jeff Burrell's FPGA bus-snooping board that mirrors video RAM writes and outputs VGA, eventually broadened to host AROS/LROS ROMs and CP/M-3 — a fundamentally new digital-path option the Yahoo era did not have.
- Regarding Improving Stock Video (#1953 on groups.io) — groups.io 2022 hands-on walkthrough of the R-78E5 + 7812 power-supply mod from David's blog (the same Vsevolod fix repackaged) — answers the practical 'where do I cut and solder' questions.
- Interesting announcements from last night's Load ZX Museum livestream (#4623 on groups.io) — Alvaro Lopes' reverse-engineering of the SCLD onto a Xilinx CPLD as a drop-in replacement, with Claudius's authoritative breakdown of TS2068 / TS2000 / TC2068 SCLD pinout differences and which exposes BRIGHT.
- YUV to RGB conversion PCB from David (#5594 on groups.io) — Working hardware prototype of the Pera-Putnik YUV→RGB circuit feeding a Sega Genesis HDMI adapter — preserves BRIGHT all the way to HDMI, the practical payoff of the 2021 BRIGHT-theory discussion.
All threads (143)
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