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Sharp X68000 ACE General Maintenance

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Sharp X68000 ACE black (Darklanlan)
A black X68000 ACE with its keyboard and a Sharp monitor (photo: Darklanlan, CC BY 4.0)

The Sharp X68000 ACE (CZ-601C) and ACE-HD (CZ-611C) went on sale in March 1988.[1] No Sharp manual for them is hosted here. The model-specific notes come from Poe, a Japanese repairer, whose ACE had a leaking backup cell and a leaking power supply.[2] The general handling advice below comes from Sharp's manuals for the original X68000 and the XVI, which agree with each other.[3][4]

Before you start

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  • The X68000 series runs from 100 V AC.[5] In countries with 220 to 240 V mains, use a step-down transformer and check its output before connecting the computer.
  • The ACE has a main switch on the rear as well as the front switch.[5] Sharp's manuals for the original model and the XVI both say: switch on at the rear and then the front, switch off at the front and then the rear, and leave at least 10 seconds between switching off and on.[3][4]
  • The ACE uses the SH2 supply and the ACE-HD the SH3.[6] Treat the primary side as live after unplugging: on the SH4 of the later models it holds more than 100 V DC.[7]

Backup cell

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The ACE's nickel-cadmium backup cell is on the control board in the base, K5710DE. On Poe's ACE it had leaked badly.[2]

  1. Remove the cell.[2]
  2. Check how far the electrolyte has spread and look for broken tracks.[2]
  3. Check the parts nearby. Poe found the cell's terminals corroded almost through, green corrosion on the contacts, and rust on pins 1 to 4 of the MC68901P, which he replaced.[2]
  4. Clean the board; see Battery Explosion, Capacitor or Corrosion Damage.
  5. Fit a replacement cell before relying on the memory switch settings. The 16 KB SRAM keeps them only while the cell is good.[5]

Power supply

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Poe photographed electrolyte leaking on an SH2 board.[2] Recap the supply, reading the value of each capacitor from the part; only C9 and C40 and C41 of the SH2 are on record, and nothing for the SH3. See the Sharp X68000 ACE Capacitor Replacement Guide.[8] Poe notes that SH2 boards come in yellow paper-epoxy and green glass-epoxy versions and that no replacement main connector is available, so handle the connector with care.[8]

Floppy drives

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The ACE's drives are the K61432-72 type. On the ACE-HD drive he serviced (version 02), Poe found the spindle motor easy to remove; he replaced the capacitors and re-greased the drive.[2]

  1. Replace the drive's electrolytic capacitors; the list for versions 03, 04 and 07 is in the capacitor guide.[9]
  2. Re-grease the mechanism.[2]
  3. On versions other than 02, leave the spindle and stepping motors in place; the head position is set against the index timing.[9]
  4. If you remove an E-ring, refit it with the sharp-edged face upwards.[9]

After servicing the drives of an ACE-HD, Poe found drive 0 ejecting discs without reading them and had not found the cause when he wrote; test both drives with a known-good disc before reassembling the case.[2]

Case cleaning

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Sharp's manuals for the original X68000 and the XVI both say to wipe the case with a soft cloth dampened with water or a mild neutral detergent, and never to use benzine or thinner, which strip or discolour the finish.[3][4]

Checklist

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  1. Confirm the mains supply is 100 V.
  2. Remove the backup cell, clean up any leak, and check the MC68901P and the tracks near it.
  3. Recap the SH2 or SH3, recording each value first.
  4. Service both floppy drives and test them.
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References

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  1. ↑ X68000, IPSJ Computer Museum, Information Processing Society of Japan—link(accessed 2026-10-21) Series table: X68000 ACE, CZ-601C, March 1988; ACE-HD, CZ-611C, 20 MB hard disk.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 X68000 ACE/ACE-HD CZ-601C CZ-611C / FDDユニット K61432-72 / 電源 SH2･SH3 修理– Poe, 2021-01-20—link(accessed 2026-10-21) Control board (base) K5710DE with the nickel-cadmium cell. Photographs: SH2 board with leakage; control board with the leaked cell; terminals corroded almost to breaking; contacts with green corrosion; after the cell and capacitors were removed, rust on pins 1 to 4 of the Motorola MC68901P, which was replaced; remove the cell, check the extent of the leak and look for broken tracks. ACE-HD drive K61432-72 version 02: spindle motor easy to remove; capacitors replaced and re-greased; afterwards drive 0 ejected discs without reading them, cause not found.
  3. ↑ 3.0 3.1 3.2 Sharp, X68000 取扱説明書 for the CZ-600C (File:Sharp X68000 CZ-600C Owner's Manual.pdf), 4.2 and 4.3, printed pages 19 and 20 (PDF pages 33 and 34): soft cloth with water or neutral detergent, no benzine or thinner; 100 V AC; at least 10 seconds between off and on; rear main switch then front switch to switch on, front then rear to switch off.
  4. ↑ 4.0 4.1 4.2 Sharp, X68000 XVI・XVI HD 取扱説明書 (File:Sharp X68000 XVI Owner's Manual.pdf), 4.2, printed page 23 (PDF page 39): soft cloth with water or diluted neutral detergent, no benzine or thinner; 4.3, printed page 24 (PDF page 40): rear then front to switch on, front then rear to switch off, 10 seconds or more between off and on.
  5. ↑ 5.0 5.1 5.2 X68000, Wikipedia (Japanese)—link(accessed 2026-10-21) Power 100 V AC; the tower models have a main power switch on the rear as well as the front switch; 16 KB battery-backed SRAM keeps the memory switch settings.
  6. ↑ X68000シリーズ電源のハンダ面から見た抵抗配置図– Kunihiko Ohnaka (kunichiko), 2020-10-10—link(accessed 2026-10-21) ACE (CZ-601C) SH2; ACE-HD (CZ-611C) SH3.
  7. ↑ X68kXVI HDの電源リペア– Fram, 2015-05-23—link(accessed 2026-10-21) The SH4's primary side holds more than 100 V DC after the plug is pulled.
  8. ↑ 8.0 8.1 SHARP X68000 修理– Poe—link(accessed 2026-10-21) Power supply table, ACE SH2: C9 180 V 390 µF, C40/C41 10 V 3900 µF; yellow (paper-epoxy) and green (glass-epoxy) boards exist; no replacement main connector.
  9. ↑ 9.0 9.1 9.2 SHARP X68000 FDD K61432-71 K61432-72 K-61435-72 修理– Poe, 2020-02-23—link(accessed 2026-10-21) K-61432-72 drive from the ACE onwards; capacitor list for versions 03, 04 and 07; E-rings are punched and have one rounded side, fit the sharp-edged side up; do not remove the spindle or stepping motor just to change capacitors, because the head position is set against the index timing.


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