Video upgrades (composite, RGB, HDMI)
Video output and upgrades — composite, RGB, S-video, VGA, HDMI mods, monitors, PAL/NTSC issues.
150 threads · 1383 messages · 2002-08-05 → 2026-10-15
The TS2068's composite and RF output has a bad reputation in the group, and the cause is well established. In the Yahoo era Adam Trionfo found his display hard to read and Bill Loguidice said every unit he had owned was noisy. In 2009 Vsevolod (vbtinfo) traced the problem to the internal 5V switching supply: small switching pulses on the +5V line disturb the SCLD (U3), so he fed U3 from its own 7805 regulator on the pad near pin 43. That became the standard power-supply/video mod. David Anderson documented it on timexsinclair.com and in a YouTube video, with an R-78E5 switching regulator as a drop-in option. In "Regarding Improving Stock Video", Frederic Freakazoid worked through which 7812 to buy, where to cut the trace, 15V still reaching pin 5 and a 4.82V rail. David also traced the audio hiss to the op amp sharing a die with the switching supply. The composite colour pots matter too: Eduardo Fuentes talked Adam through adjusting them, and pointed out that the 2068's SCLD lets BRIGHT affect black, which the Spectrum's ULA does not.
The modern route is RGB. David sells an RGB monitor adapter that feeds a Hyperkin Sega Genesis HDMI cable. Adam and Carl Miles reported a rock-stable picture with accurate colours (checked with Eduardo's colortest.tzx), but the SCLD's RGB pins carry no intensity bit, so BRIGHT colours are lost. Eduardo weighed ways to recover BRIGHT, and Richard Atkinson explained how the Spectrum and 2068 Y signals differ. David built a prototype YUV-to-RGB board based on Pera Putnik's MSX-derived schematic and the LM1889 inputs. Carl finished it in 2024 to keep BRIGHT through HDMI conversion, though it needs soldering inside the machine. Jeff Burrell proposed an FPGA board on the expansion bus that mirrors video RAM writes and outputs VGA. Members also pointed to ZX-VGA-JOY, ZX-HD and ULAplus. The FPGA video board that later shipped is VGA-only with eight colours, and the PicoVideo adds a 3.5mm audio out. Adam found it made OS-64 usable.
The hardware context came from the Portuguese side. Claudius explained that the TC2068 exposes all four RGBI signals on the edge connector, while the US TS2068 SCLD has no I line and cannot produce component video. Paulo Leite converted a black TC2068 to NTSC/60Hz by moving two jumpers and changing the crystal. Alvaro Lopes of the LOAD ZX Museum recreated the TC2068/TC2048 SCLD as a drop-in CPLD board. Smaller threads covered Luis Antoniosi's S-video amp, a dead ZX8-CCB composite mod in Adam's TS1000, and finding a ZX80's UHF channel. Several threads in this set only drifted into video: the ZX Spectrum ROM and NTSC Spectrum discussions, the 64-column/OS-64 documents, Charlie Day's alpha ROM (ULAplus testing in patched FUSE), the TS1000-to-TS1500 conversion and the switchable-ROM mod.
Key threads
- Video Blurry; was: TS 2068 - Sound/Hissing Problem (#1831 on groups.io) — Where vbtinfo traced the noisy picture to the 5V switching supply and fixed it by feeding the SCLD from its own 7805.
- Regarding Improving Stock Video (#1168 on groups.io) — Walk-through of the power-supply/video mod from David's article: 7812 and R-78E5 parts, the trace cut, pin 5 voltages, plus the origin of the audio hiss.
- My New 2068 Toys/RGB Monitor Adapter Works - Hooray! (#651 on groups.io) — David's RGB adapter with a Sega Genesis HDMI cable in practice, colortest.tzx comparisons, and monitor choices such as the EM12A.
- A sad day... (#1503 on groups.io) — Branches into the HDMI converter test, where Carl confirms a clean picture but no BRIGHT colours over RGB.
- Topics for Next Timex Sinclair Zoom Meeting (End-of-July?) (#1529 on groups.io) — Eduardo's options for adding BRIGHT to RGB and Richard Atkinson's explanation of how the Spectrum and 2068 Y signals differ.
- YUV to RGB conversion PCB from David... (#776 on groups.io) — Prototype YUV-to-RGB board that keeps BRIGHT through HDMI, with its schematic sources and the trade-off of soldering inside the machine.
- Video Upgrade Board for TS2068 (#1345 on groups.io) — Jeff Burrell's FPGA VGA board proposal, plus pointers to ZX-VGA-JOY, ZX-HD and ULAplus.
- Interesting announcements from last night's Load ZX Museum livestream (#874 on groups.io) — Alvaro Lopes's CPLD SCLD replacement and Claudius's breakdown of RGBI on the TC2068 versus RGB on the TS2068.
- Inspired to Play the 2068 (#1585 on groups.io) — Adjusting the composite colour pots, and the 2068's BRIGHT-black difference from the Spectrum.
- NTSC Spectrum (#1849 on groups.io) — PAL/NTSC background, including Paulo Leite's two-jumper-and-crystal NTSC conversion of a TC2068.
All threads (150)
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