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Sharp MZ-80C Capacitor Replacement Guide

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Sharp MZ-80K power supply circuit (service manual)
Power supply of the European MZ-80K, from Sharp's service manual. The MZ-80C's 100 V supply is a different unit and has no published schematic.

No capacitor values have been published for the Sharp MZ-80C. SharpMZ.net, which hosts Sharp's MZ-80K service manual, lists only a Japanese owner's manual for the C, and the MZ-80K manual covers only the European MZ-80K.[1][2] The C shares the MZ-80K's basic design but has a green monitor, a typewriter-layout keyboard, 48 KB of RAM and a 100 V Japanese power supply, and Japanese Wikipedia notes that it used more expensive components than the MZ-80K.[3] The MZ-80K's values are in the Sharp MZ-80K Capacitor Replacement Guide. They are a comparison for the C's CPU board and cassette deck at most; the C's power supply and monitor are different units.

What is known

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  • The European MZ-80K's power supply has four 10 µF 35 V tantalum capacitors (C401, C501, C502 and C509) that owners report shorting, with smoke or a blown mains fuse.[2][4] Whether the C's 100 V supply uses tantalums in the same places is not documented, so look for them first.
  • The MZ-80K's CPU board has two tantalums, C39 (33 µF 10 V) and C41 (10 µF 35 V), and 100 µF 25 V capacitors C36, C37 and C38 on its +12 V, +5 V and −5 V inputs.[5] Adam Wilson replaced all the tantalum and aluminium capacitors on his MZ-80K's CPU board.[6]
  • The MZ-80K's monitor board values are for its black and white 240NB4 display and do not apply to the C's green monitor.[2]

Recording your own board

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  1. Unplug the machine and open it; the MZ-80K procedure is in Sharp MZ-80K General Maintenance#Opening the case. Discharge the CRT before touching the monitor board, following the CRT Discharge Procedure.
  2. Photograph each board before removing anything.
  3. For each electrolytic and tantalum capacitor, write down the designator, the capacitance, the voltage, the type and the polarity mark.
  4. Compare the CPU board and cassette board lists with the Sharp MZ-80K Capacitor Replacement Guide.
  5. Replace like for like: the same capacitance and at least the same voltage. On a negative rail (−5 V on the MZ-80K) the positive lead goes to ground.[7]
  6. After work on the supply, measure its outputs at the CPU board before refitting the other boards.
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References

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  1. ↑ MZ-80K Manuals, SharpMZ.net—link(accessed 2026-10-21) Lists the "Japanese MZ-80C Manual" and the MZ-80K Service Manual.
  2. ↑ 2.0 2.1 2.2 Sharp Corporation, Service Manual, Personal Computer MZ-80K (File:Sharp MZ-80K Service Manual.pdf): covers the MZ-80K with the 220 V power supply DBOXD0004PAZZ and the UK 240 V unit DBOXD0005PAZZ, a 10-inch black and white display (DUTT0004PAZZ) and a 78-key keyboard; replacement parts list, printed pages 43 to 47. Hosted with a description at Sharp MZ-80K Service Manual.
  3. ↑ MZ-80, Wikipedia (Japanese)—link(accessed 2026-10-21) MZ-80C (1979): same basic design as the MZ-80K; 48 KB RAM; full typewriter-layout keyboard; green monitor; more expensive parts than the MZ-80K. MZ-80K series in Japan: AC 100 V ±10 % 50/60 Hz.
  4. ↑ Sharp MZ-80K Power Supply repair– xAD / nIGHTFALL, nIGHTFALL Blog, 2013-01-13—link(accessed 2026-10-21) Four short-circuited tantalum capacitors in an MZ-80K power supply replaced with electrolytic capacitors; owners report smoke and the 500 mA fuse F101 blowing.
  5. ↑ Sharp, MZ-80K service manual (File:Sharp MZ-80K Service Manual.pdf), parts list, printed page 44 (PDF page 46): C36 to C38 100 µF 25 V aluminium; C39 33 µF 10 V tantalum; C41 10 µF 35 V tantalum; and circuit diagram (10) of the CPU board, printed page 35 (PDF page 37).
  6. ↑ 1980 Sharp MZ-80K Repair & Restoration– Adam Wilson, Adam's Vintage Computer Restorations, 2026-01-31—link(accessed 2026-10-21) Tantalum and aluminium electrolytic capacitors on the MZ-80K mainboard replaced.
  7. ↑ Sharp, MZ-80K service manual (File:Sharp MZ-80K Service Manual.pdf), power supply wiring diagram, printed page 37 (PDF page 39), and CPU board circuit diagram (10), printed page 35 (PDF page 37): C201, C202 and C38 on −5 V with the positive side to ground.


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