Jump to content

Sharp MZ-1500 Capacitor Replacement Guide

From RetroTechCollection
Sharp MZ-1500
MZ-1500 (photo: うぃき野郎, CC BY-SA 4.0). The power supply sits inside the case as a separate board in a metal cover.

The Sharp MZ-1500's best-documented electrolytic capacitors are those in its internal power supply. The owner Ohishi recapped the supply after it became too weak to run the kanji ROM boards, and published the list of its electrolytics with the parts he fitted.[1] No Sharp parts list for the MZ-1500 has been found online. The main board's electrolytics can be read from the complete circuit diagram printed in Radio Gijutsu-sha's Sharp MZ-1500 Technical Note (1984), which gives their values but, for all but two, no voltage ratings.[2]

Warning: the power supply runs from the mains. Unplug the machine and let the supply's capacitors discharge before working on it; C4 is rated 200 V.

Power supply

[edit | edit source]
MZ-1500 power supply electrolytics (Ohishi)
Ref Fitted at the factory Ohishi's replacement Notes
C4 150 µF 200 WV 150 µF 450 V The largest capacitor in the supply; the 450 V part is taller than the original
C5 3.3 µF 200 V 3.3 µF 250 V
C9 33 µF 35 V 33 µF 35 V
C10, C11, C12 1000 µF 10 V 1000 µF 10 V

[1]

Ohishi chose the replacements by keeping each capacitance and fitting a voltage rating no lower than the original. He found no 200 V part of the right size for C4, so he used a 450 V one; it had the same diameter but was taller, and the supply's metal cover only just closed over it.[1] A 200 V or 250 V part of the same capacitance is usually smaller, so look for one before settling on 450 V. "WV" on the original C4 is the working voltage, read as an ordinary voltage rating.[1]

Before the recap, Ohishi's supply showed no leakage and no clear swelling, only one black capacitor that looked slightly domed, yet it could no longer run the machine with the kanji boards fitted. He replaced every electrolytic, because capacitors that have lost capacitance often look normal.[1]

Main board

[edit | edit source]

The Technical Note circuit diagram shows these polarised capacitors on the main board. Page numbers are the book's printed pages.[2]

MZ-1500 main board polarised capacitors (Technical Note circuit diagram)
Ref Value on the diagram Position in the circuit Page
C50 100 µF Across the +5 V input from the power supply, connector T-1 219
C88 33 µF 16 V +5 V line beside the RAM at 18K 219
C14 3.3 µF Power-on reset, with R23 and the reset IC Q2 (PST518B-2) 219
(no number) 1 µF 50 V Reset switch, with R31 219
C28 100 µF Across the 5 V and ground pins of the data recorder connector T-9 216
C11 1 µF Data recorder sense line, at LS14 4A 216
C27 22 µF Data recorder sense line, after LS14 4A 216
C10 1 µF Output to the cassette WRITE socket T-4 216
C3 1 µF Input from the cassette READ socket T-5 217
C4 10 µF Cassette read input circuit, with D5 and D6 217
C5 100 µF 556 timer at 1B, with R4 and R5 216
C8 1 µF 556 timer at 1B, with R6 and R7, beside the joystick connectors 217
C99 10 µF 8253 sound into the audio input of the SN76489 at 4F 222
C29 10 µF Voice board (T-15) into the audio input of the SN76489 at 3F 222
C16, C17 4.7 µF Left and right line outputs to T-13 223
C18 10 µF Mixed sound to the volume control VR1 223
C64, C87 10 µF LM386 speaker amplifier at 1I 223
C62 220 µF LM386 output to the speaker connector T-3 223

[2]

Only C88 (16 V) and the reset switch capacitor (50 V) have voltage ratings on the diagram. Before ordering, read the rating printed on each part on your own board. Everything on the main board runs from the power supply's single 5 V output.[1] Fit replacements of at least the voltage printed on the originals. The diagram covers neither the power supply nor the Quick Disk drive's own circuit board, whose values are not published.

To check your board against the diagram:

  1. Photograph the board from above before removing any part.
  2. Match each electrolytic's printed reference to the table, and note its voltage and temperature rating and which way its negative stripe faces.
  3. Note any part that is not in the table, or a value that differs, with the board marking and revision.

Replacement procedure

[edit | edit source]
  1. Unplug the machine and open the case. Take the power supply out in its metal cover, noting how its leads connect to the rear power switch and the main board.
  2. Photograph the supply board and note the polarity of every electrolytic.
  3. Replace C4, C5, C9 and C10 to C12 with parts of the same capacitance and at least the same voltage. On the main board, work through the table above in the same way.
  4. Check that the new C4 clears the cover before closing it.
  5. Reconnect the supply and measure its 5 V output before refitting the main board's lead.
  6. Reassemble and test with your usual option boards fitted. On Ohishi's machine, kanji drawn cleanly with the kanji ROM and dictionary ROM boards in the main slot showed that the supply was healthy again.[1]

Replacing the supply instead

[edit | edit source]

The supply has a single 5 V output, so a modern 5 V switching supply can replace it. Ohishi fitted a 2 A unit and it ran his machine, though the 28 W rating suggests a larger supply would be safer if one fits.[1][3] Details are in General Maintenance.

[edit | edit source]

References

[edit | edit source]
  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 MZ-1500– Ohishi—link(accessed 2026-10-21) Owner's page, section "MZ-1500のメンテナンス", "ケース2：電源のコンデンサを交換する": list of the electrolytic capacitors used in the MZ-1500's power supply and the replacements bought (C4 150 µF 200 WV replaced with 150 µF 450 V; C5 3.3 µF 200 V with 3.3 µF 250 V; C9 33 µF 35 V with 33 µF 35 V; C10, C11 and C12 1000 µF 10 V with 1000 µF 10 V); the capacitance must match, the voltage rating may be higher but not lower, and higher-voltage parts are larger, so check the fit; C4 is the largest capacitor, its replacement had the same diameter but was taller and the supply's metal case only just closed; before the recap no capacitor had leaked and none was clearly swollen, though one black capacitor looked slightly swollen; supply failure usually comes from electrolytics losing capacitance, which does not always show, so replace them all; the supply has a single 5 V output; after recapping, the corrupted kanji no longer appeared.
  2. ↑ 2.0 2.1 2.2 Nihon Maikon Kurabu (ed.), Sharp MZ-1500 Technical Note (シャープ MZ-1500 テクニカルノート), Radio Gijutsu-sha, Radio Gijutsu Sensho 151, first edition 15 December 1984; scan on the Internet Archive. Appendix 2, "MZ-1500の全回路図" (complete circuit diagram), pages 216 to 223. Polarised capacitors drawn: page 216, C28 100 µF across the +5 V and ground pins of the data recorder connector T-9, C11 1 µF and C27 22 µF on the sense line at LS14 4A, C10 1 µF in the output to the cassette WRITE socket T-4, C5 100 µF on the 556 timer 1B with R4 and R5; page 217, C8 1 µF on the 556 timer 1B with R6 and R7 beside the joystick connectors T-10 and T-11, C3 1 µF and C4 10 µF in the input from the cassette READ socket T-5; page 219, C14 3.3 µF with R23 on the power-on reset from Q2 (PST518B-2), an unnumbered 1 µF 50 V capacitor with R31 on the reset switch, C50 100 µF with C100 (0.1 µF) across the +5 V input connector T-1, C88 33 µF 16 V beside the RAM at 18K; page 222, C99 10 µF from the 8253 sound line into the audio input of the SN76489 at 4F, C29 10 µF from the voice board connector T-15 into the audio input of the SN76489 at 3F; page 223, C16 and C17 4.7 µF to the left and right outputs on T-13, C18 10 µF from the mixed sound to the volume control VR1, C64 and C87 10 µF on the LM386 amplifier at 1I, C62 220 µF from the LM386 output to the speaker connector T-3. The diagram does not include the power supply or the Quick Disk drive's own board.
  3. ↑ MZ-1500, Wikipedia (Japanese)—link(accessed 2026-10-21) Power 100 V AC ±10%, 50/60 Hz, 28 W.


Retrieved from "https://retrotechwiki.com/index.php?title=Sharp_MZ-1500_Capacitor_Replacement_Guide&oldid=28610"