Repair & restoration
Repair and restoration — power supplies, capacitors, keyboard membranes, dead machines, diagnostics, recapping.
185 threads · 1388 messages · 2002-11-12 → 2026-06-08
Repair and restoration is one of the most active threads on the list across both eras, but the cast and tooling changed dramatically. In the Yahoo era (2001–2019) the resident diagnostician was Eduardo Fuentes in Argentina, and the entire fault tree the group still uses for a dead 2068 was first laid out by him: suspect a faulty UA78L12 regulator near the video modulator or a bad LM1889 in the modulator box for missing video; piggy-back a known-good 4416 onto U12/U13 (8000–BFFF) or U17/U18 (C000–FFFF) to isolate bad upper RAM; turn the machine on and feel each lower-RAM chip with a fingertip — the hot one is the culprit. The other defining Yahoo-era contribution came from vbtinfo (Vsevolod) in 2008–2009: scoping the +5V rail he found small switching pulses leaking from the internal SMPS into U3 (the SCLD), proved it was a design flaw rather than a fault, and published the mod that adds a Radio Shack 7805 to power the SCLD directly off the pad near pin 43 (lifting the original jumper to C67). That mod is the direct ancestor of every modern 'clean up the 2068 video' recipe.
In the groups.io era (2020→) the bench work moved to Carl Miles in New Mexico, who functions as the group's de-facto repair shop — diagnosing and reviving dead machines mailed in by Ryan Gray, Ian, the Bill Miller collection, and others, and posting step-by-step narratives. Carl's flagship 2023–24 thread on Ian's and Ryan's two TS2068s walks the standard fault tree at length: a working 'parts' TS2068 painted up; Ryan's original 1983 machine getting all six memory chips and the Z80 replaced; the long-dead 30-year donor unit rebuilt into a working test mule, with Carl bodge-wiring sockets onto all the chip positions for future swap-testing. The parallel ZX Spectrum 48K thread treats Bill Miller's A&J-Microdrive-converted Spectrum as a separate exercise: Carl maps every electrolytic, hands the table back for sign-off before recapping, accidentally shorts the -5V rail while probing, and ends up with a noticeably-cleaner-than-stock video — plus a vDrive ZX demo where CATalog timing turns out to match a real Microdrive.
Power supplies are the single most-discussed failure mode in both eras. The Yahoo archive carries the reprinted UPDATE Jan. '89 warning blaming voltage-regulator failures for roughly 150,000 abandoned TS-2068s, and the groups.io consensus is built on top of it: move to a modern switching brick, replace the original 5V switching regulator with an R-78E5 drop-in (which also kills the audio hiss Vsevolod first traced to SMPS noise), and use Jameco #191652 (15VDC 1A) as the canonical replacement adapter. A live caution in both eras: peripherals like the ZX Printer, Interface 1 and Microdrives pull the unregulated 9V line directly, and the internal DC-DC converter derives +12V/-12V/-5V from it, so higher unloaded voltage from a modern adapter matters. The TS1500/TS1000 ULA story closed a long-running gap with vretrodesign's VLA81 drop-in replacement (Patrick Leclerc surfaces the link in Carlos Nunez's TS1000-help thread).
Carl's TS1000→TS1500 conversion project sits adjacent to repair: RAM upgrade to 16K, 7805 swap for a switching regulator, composite mod on the TV output, TS1500 ROM in the existing socket (optional unless you want TS1510 cart auto-run), and the silver/gray paint scheme to match the TS1500/TS2068 family — Krylon Short Cuts from Hobby Lobby, masking carefully around the white jack lettering and FCC label. Frederic Freakazoid's recap-and-improve-video project on four TS2068s ('Regarding Improving Stock Video') walks through David's blog recipe and Carl's TS2050 painting thread runs the same paint-and-rebadge playbook on a cracked-in-two modem case. Still-open hard problems carried forward: sourcing the custom TS2068 SCLD (no modern equivalent; the CATS newsletter lead on ~100 spares via Mark Fisher is the current best hope, found while Carl was researching the TS2050-to-RS232 conversion); the lack of a dedicated 2068 diagnostic cartridge (a TS-Pico autoboot diag is the workaround Jeff K suggested); and the open question from Josef Jelinek's 'Any TS2068 PCB updates?' thread of whether a faithful 2068 clone (Claudius's WiP board, Don Dindang's Harlequin-2048) should match the TC2048/2068 /INT timing — shifted 15 T-states from Spectrum, which is what makes top-border demos crash on real Portuguese hardware. A characteristic groups.io-era detail: repair has become social. The ABQ in-person meetings double as a repair bench (Carl examines Adam's ZX8-CCB composite mod live on May 13, 2023 and finds the NAND gates 'too hot to touch' / dead), and Carl's narrative posts effectively serve as the documentation the machines never had when they were new.
Key threads
- Video Blurry / Video fix for TS2068 (archive.org) — Vsevolod scopes the +5V rail, proves SMPS noise into the SCLD is a design flaw not a fault, and publishes the Radio Shack 7805 mod that powers the SCLD directly off the pad near pin 43 — the direct ancestor of every later 'clean up 2068 video' recipe.
- TS2068 Repairs Dec 2023 -- Ian's and Ryan's TS2068s (#5242 on groups.io) — Carl's flagship repair narrative — sockets on every position, six memory chips and the Z80 replaced in Ryan's original 1983 machine, the 30-year dead donor rebuilt into a working test mule. The canonical groups.io-era repair thread.
- ZX Spectrum 48K Repair (Bill Miller Collection) (#5525 on groups.io) — Carl recaps an A&J-Microdrive-converted Spectrum, accidentally shorts the -5V rail while probing, and ends up with measurably cleaner video — plus a vDrive ZX demo where the SD-card CATalog turns out to match a real Microdrive's timing.
- Regarding Improving Stock Video (#1953 on groups.io) — Frederic Freakazoid recaps four TS2068s following David's blog recipe — the canonical 'I have a working 2068 and want to make it better' workflow, with David debugging the 15V-into-pin-5 trace question over weeks.
- T/S 2068 Power Supply Replacement (#773 on groups.io) — Adam asks for a beefier supply after his divMMC hangs the 2068 mid-boot; Richard Burt names Jameco #191652 (15VDC 1A) as the TTSUG-blessed answer; Carl explains the original SMPS topology so newcomers can understand why a 'bigger cap' isn't the fix.
- TS1000 -> TS1500 Conversion Project (#5664 on groups.io) — Carl's recipe in one place: 16K RAM upgrade, 7805→switching, composite mod, TS1500 ROM, silver/gray Krylon Short Cuts paint with masking around the white jack lettering and FCC label. The community 'modernize a TS1000' canon.
- Potential source for the TS2068 SCLD Chip? (#5478 on groups.io) — Carl finds a CATS newsletter mention of ~100 SCLD spares purchased for future repair while researching the TS2050-to-RS232 conversion — the still-open SCLD-sourcing problem and its best current lead.
- Any TS 2068 main PCB updates? (#6932 on groups.io) — Josef Jelinek's question opens the modern-clone-board debate — Claudius's WiP redesign, Don Dindang's Timex-Harlequin-2048 fork that adds TS2068 home/ext ROM but no DOCK yet, and Claudius flagging the /INT timing 15 T-state shift that crashes top-border demos on real Portuguese hardware.
- Slightly off topic… TS1000 Help (#6651 on groups.io) — Carlos Nunez can't tell if his TS1000 works; Patrick Leclerc surfaces vretrodesign's VLA81 ZX81 ULA drop-in replacement — closes a long-running ZX81-family ULA-sourcing gap.
- I Got My Spectrum divMMC Today! (#639 on groups.io) — Drift-into-repair: Adam's divMMC boots intermittently, and Neil C. surfaces the 1989 UPDATE article warning that 5V 1A regulators were speced for 2040 printer + dock carts, not modern peripherals — explains exactly why every modern interface pushes the original supply over the edge.
All threads (185)
↳ marks a thread where this topic begins mid-conversation — the link jumps to the message where it starts.