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Sharp X1 & MZ

Sharp's Z80 lines in Japan, before the X68000: the MZ series ("clean computer", BASIC loaded from cassette) from 1978, and the X1 series (1982) marketed as "pasokon + TV". Good JP game library, a demoscene presence. Standard JP 8-bit repair: recap, drive, keyboard.

Sharp MZ-700

Sharp MZ-700 — photo by Bilby, CC BY 3.0 (Wikimedia Commons).

Identification

Line Years CPU Note
MZ-80K / 700 / 1500 1978-84 Z80 "clean computer", all-in-one (screen + cassette/QD)
MZ-2000 / 2500 1982-85 Z80 high-end, improved graphics
X1 / X1 turbo 1982-84 Z80 TV overlay, text/PCG cards, optional FM

Sound: PSG (AY/SN) + FM (YM2151) on X1 turbo/high-end; cassette / Quick Disk / floppy media.

Clocks & frequencies ✅

Component Frequency Role / scope
Zilog Z80 4 MHz X1 (modèles améliorés — la vitesse d'horloge est restée à 4 MHz)
Zilog Z80B 6 MHz MZ-2500 (SuperMZ), à partir de 1985

Careful not to mix the two lines: X1 and MZ are two distinct Sharp families with different clock rates.

Why this matters in repair

A clock that is missing or off-value on a frequency counter points straight at the crystal, its divider chain or the component it feeds — the fastest starting point on a machine that will not boot. Source: Wikipedia (CC-BY-SA).

Repair (technician)

  • Recap (PSU + board; all-in-one models = many electrolytics) → Recap.
  • Drive: cassette / Quick Disk / floppy → mechanism, belts (common on integrated MZ units).
  • Integrated screen (MZ): it is a CRT → see CRT safety before working.
  • Keyboard: contacts → clean.
  • Video (X1): RGB output / overlay → check wiring.

Procedure — a dead computer, step by step ✅

There is a CRT inside this machine

The tube holds its charge with the machine unplugged, and on these all-in-ones the analogue board sits right where your hands go. Discharge it, or work on the logic board out of the case. → CRT safety

What this adds

Ordered for a home computer: what kills these is its power supply, its battery, its capacitors, its socketed RAM and its keyboard — roughly in that order, and well before the CPU. → PCB diagnosis

1. The power supply — measured before it is plugged in. This is the one step not to swap around. On a machine of this age a supply does not simply stop: a 5 V regulator that fails high puts 7, 9, 12 V onto the bus and takes the RAM and the custom chips with it. Measure every rail off the machine, under a dummy load if you can, and only then plug it in.

2. The battery, if it has one. Any RTC or backup cell soldered to a board is a future leak. If yours has one and it has never been changed, take it out before it takes the tracks with it. → Backup batteries

3. Capacitors. Recap is the default on these machines, not a last resort — and on the supply first, since that is what protects everything else. → Recap

4. RAM, on its sockets. These machines were built to be repaired: the RAM, and often the logic, sit in sockets. Reseat everything first — thirty years of oxide is a classic no-boot. Then swap chips: a bad RAM chip usually gives a repeatable pattern of garbage or a screen frozen at a fixed character.

5. The keyboard. A console does not have one; a computer's is a wear part. A membrane keyboard fails as whole dead rows or columns — that is the membrane, not the machine. A mechanical one wants its contacts cleaning, not replacing. Check this page: the failure mode is often documented per model.

6. Storage — tape or disk. Both often come down to the same things: a dirty head, and for tape the azimuth and a belt turned to tar. ⚠️ On the floppy side, check whether the mechanism actually has a belt before looking for one: many do, but some drives are direct drive, and hunting a belt that isn't there means stripping a drive for nothing. A machine that boots but loads nothing is a drive fault, not a logic fault — do not go looking on the board for it.

7. Video output. RF, composite, RGB or a dedicated monitor, depending on the machine (see Identification). Test with something else before you conclude: a period modulator and a modern TV disagree far more often than either is broken.

8. Still nothing. Now the logic: rails on the board, reset, clock, bus. → PCB diagnosis

Common faults

Symptom Likely cause Lead
Won't load drive (belt/head) Mechanism, belts
Instability caps Recap
Dead picture (all-in-one MZ) CRT / video board CRT safety first
Dead keys keyboard Clean

Modernisation & mods — what to buy, how

All-in-one MZ = CRT high voltage + recap

All-in-one MZ units contain a CRT: high voltage, discharge the tube before opening → CRT safety. Substantial recap (all-in-ones have many electrolytics); change drive/tape belts.

Modern storage - Gotek + FlashFloppy or HxC 🟡 for the floppy drives (X1, floppy-based MZ); Quick Disk emulators 🟡 for the MZ/X1 that use them. - Cassette → audio 🟢 from a PC/phone (.wav/.cas images) for tape models (many MZ).

Video - RGB output (X1) 🟢 → SCART then OSSC / RetroTINK or RGB2HDMI. (All-in-one MZ: no "color mod", the display is the built-in CRT.)

⚠️ Do not host ROMs/games — method only.

See also

Sources & attribution

Review & corrections

How this space is used

Spotted a wrong value, an outdated procedure, a chip reference that does not match your board? Say so here, with what you observed (model, board revision, serial number, measurement). Every report is cross-checked against a source before anything changes — an unverifiable correction is published as “reported by …, not cross-checked” rather than silently applied.

Reading is open to everyone; posting requires signing in with Discord. Reports from the wiki's declared reviewers are handled first; anyone else's are read too, but go through a human before anything is changed.