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Sharp X68000 EXPERT Capacitor Replacement Guide

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Sharp X68000 XVI power supply schematic (service manual)
Sharp's circuit diagram of the SH4 power supply from the X68000 XVI service manual; the EXPERT uses the same board

The Sharp X68000 EXPERT (CZ-602C, CZ-612C) and EXPERT II (CZ-603C, CZ-613C) use the SH4 power supply, the same board as the Sharp X68000 SUPER, Sharp X68000 XVI and Sharp X68030.[1][2] The supply's capacitor values come from Sharp's diagram in the Sharp X68000 XVI Service Manual, and the procedure for removing, recapping and testing it is on the Sharp X68000 XVI Capacitor Replacement Guide. The EXPERT's own boards are different designs, and no capacitor list has been published for most of them. What is known is set out below, with the places where the values have to be read from the board.

Warning: the supply runs from 100 V mains, and the primary side keeps more than 100 V DC on C9 after the plug is pulled. Unplug the machine and measure across C9 before touching the primary side.[3]

Power supply (SH4)

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Sharp's diagram shows 13 electrolytics in the SH4: C9 (470 µF 180 V), C24 (1000 µF 25 V), C25 (680 µF 16 V), C27 (220 µF 25 V), C28 (100 µF 16 V), C31 (100 µF 10 V), C33 (220 µF 16 V), C34 (100 µF 6.3 V), C35 (10 µF 25 V), C38 (3.3 µF 50 V), C40 and C41 (5600 µF 10 V) and C42 (2200 µF 6.3 V).[4] The table with each part's position, Poe's replacement voltages and the notes on leaks are on the XVI capacitor guide.

  • Fit C27, C28 and C31 by the silkscreen on the board. Fram found that Sharp's diagram draws all three with the wrong polarity.[5]

Boards

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EXPERT and EXPERT II boards and what is known about their capacitors
Board EXPERT EXPERT II Capacitors
Main board K6247DE K6708DE No list published
Base (control) board K6248DE K6709DE No list published
Analogue board K6249DE K6710DE No list published
Expansion slot board K6250DE K6711DE EXPERT II: four 47 µF 10 V
External interface board K6251DE K6712DE, K6713FD No list published

[2] Poe photographed the EXPERT's base and analogue boards and the EXPERT II's, but did not list their capacitors.[2] Record the value, voltage and polarity of each part before removing it. Sharp's XVI diagrams show the kind of parts to expect: the XVI's control board in the base has 36 electrolytics from 0.47 µF to 100 µF, and its analogue board has three 470 µF 10 V output capacitors and five 100 µF parts.[6] The EXPERT boards are not the same design, so do not order from the XVI list without checking.

On Sharp's XVI diagram the slot board's capacitors on the +12 V and −12 V lines are 16 V parts.[6] If the EXPERT II's four 47 µF parts are all 10 V, as Poe lists them, check which of them sit on the 12 V lines before fitting replacements, and use 16 V or higher there.

Floppy drives

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The EXPERT's drives are the K61432-72 type used from the ACE to the X68030. Poe lists the capacitors of versions 03, 04 and 07 of that drive: C13, C18, C20 and C22 (100 µF, Nichicon N728 low-profile), C10, C24 and C26 (10 µF 16 V), and unnumbered parts of 22 µF 16 V (five), 10 µF 16 V, 1 µF 50 V and 1 µF 50 V bipolar. His version table gives the four 100 µF parts as 6 V, his stock list as 16 V.[7] The drive he repaired from an EXPERT was version 05, on which the capacitors at the spindle motor are easy to reach.[2] Read the cans on your drive before ordering, and do not remove the spindle or stepping motor to reach a capacitor.[7]

Keyboard

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No capacitor list has been published for the EXPERT's keyboard. The original X68000 keyboard and the XVI keyboard both have two electrolytics, C3 (2.2 µF 50 V) and C8 (100 µF 10 V).[8][6] Check your board.

Replacement procedure

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  1. Recap the SH4 first, following the XVI procedure: unplug, discharge and measure C9, photograph the board, clean off any electrolyte, replace burnt parts, fit C27, C28 and C31 by the silkscreen, and test the supply on the bench.[3][5]
  2. On the boards, photograph each one and write down every capacitor's value, voltage and polarity before removing any.
  3. Replace one capacitor at a time with the same value and an equal or higher voltage.
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References

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  1. ↑ 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) EXPERT, EXPERT-HD, EXPERT II and EXPERT II-HD use the SH4, as do the SUPER, XVI and X68030.
  2. ↑ 2.0 2.1 2.2 2.3 X68000 EXPERT CZ-602C CZ-612C / EXPERT II CZ-603C CZ-613C / FDDユニット K61432-72 修理備忘録– Poe—link(accessed 2026-10-21) EXPERT: SH4, main K6247DE, analogue K6249DE, base K6248DE, slot K6250DE, external interface K6251DE; photographs of the base and analogue boards. EXPERT II: SH4, main K6708DE, analogue K6710DE, base K6709DE, slot K6711DE (four 47 µF 10 V), external interface K6712DE and K6713FD; photographs of the base and analogue boards. Repair of an EXPERT's drive K61432-72, version 05: head shaft lubricant hardened, cleaned and re-greased, all capacitors replaced; the spindle motor capacitors of version 05 are easy to change.
  3. ↑ 3.0 3.1 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; leaking capacitors, burnt parts and a blown fuse; the supply can be tested on its own.
  4. ↑ Sharp, service manual CZ-134 for the X68000 XVI (File:Sharp X68000 XVI Service Manual.pdf), 22, power supply basic wiring diagram, printed pages 97 and 98 (PDF page 85): SH4 board UADP-0069CEZZ with C9 470 µF 180 V, C24 1000 µF 25 V, C25 680 µF 16 V, C27 220 µF 25 V, C28 100 µF 16 V, C31 100 µF 10 V, C33 220 µF 16 V, C34 100 µF 6.3 V, C35 10 µF 25 V, C38 3.3 µF 50 V, C40 and C41 5600 µF 10 V, C42 2200 µF 6.3 V. See Sharp X68000 XVI Service Manual.
  5. ↑ 5.0 5.1 【訂正】X68kの電源ユニットのシルク印刷に間違いがあった件&X68kの電源修理再び(未完)3– Fram, 2024-03-24—link(accessed 2026-10-21) The SH4 diagram draws C31, C27 and C28 with reversed polarity; the silkscreen is correct. Fram notes that the SH4 is used from the EXPERT to the XVI and in the PRO II.
  6. ↑ 6.0 6.1 6.2 Sharp, service manual CZ-134 (File:Sharp X68000 XVI Service Manual.pdf): XVI control board, 36 electrolytics from 0.47 µF to 100 µF (printed pages 85 and 86, PDF page 78); expansion slot lines C803 and C804 47 µF 16 V on +12 V and −12 V, C801 and C802 47 µF 10 V on the +5 V lines (printed pages 89 and 90, PDF page 80); analogue board C403 to C405 470 µF 10 V and five 100 µF parts (printed pages 93 and 94, PDF page 83); keyboard C3 2.2 µF 50 V, C8 100 µF 10 V (printed pages 101 and 102, PDF page 87).
  7. ↑ 7.0 7.1 SHARP X68000 FDD K61432-71 K61432-72 K-61435-72 修理– Poe, 2020-02-23—link(accessed 2026-10-21) Versions 03, 04 and 07: C13, C18, C20, C22 100 µF 6 V Nichicon N728 low-profile; C10, C24, C26 10 µF 16 V; five 22 µF 16 V, one 10 µF 16 V, one 1 µF 50 V and one 1 µF 50 V bipolar, unnumbered. Stock list for the K-61432-72 gives the 100 µF parts as 16 V. Do not remove the spindle or stepping motor just to change capacitors.
  8. ↑ SHARP X68000 修理– Poe—link(accessed 2026-10-21) CZ-600C keyboard: C3 2.2 µF 50 V and C8 100 µF 10 V.


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