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Sharp MZ-2000 Troubleshooting Guide

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Sharp MZ-2000 power supply circuit (owner's manual)
MZ-2000 power supply: mains fuse F101, transformer with thermal fuse, the +12 V and +5 V switching regulators with fuses F41 and F21, and the +15 V and −5 V linear regulators (Sharp owner's manual, figure 4-18)

Fault-finding on the Sharp MZ-2000 starts with the power supply, then the CPU board, the display unit and the cassette deck. Component references come from the circuit diagrams in Sharp's Japanese owner's manual, hosted at Sharp MZ-2000 Owner's Manual.[1] Sharp published no fault-finding procedure for the MZ-2000; the owners' reports below are from Ohishi's pages on his own machine.

Warning: mains voltage is present on the power supply and its wiring, and the built-in monitor runs at about 11 kV. Unplug the machine before raising the upper cabinet, and see CRT Discharge Procedure before working on the display board.

Quick reference

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Symptoms, causes and actions
Symptom Probable cause Action
Completely dead Mains fuse F101, switch, transformer thermal fuse No power
Power on but nothing happens: no lid opening, no message +5 V missing (F21), logic fault No start-up
Internal screen dark or distorted, external colour monitor normal Display unit: fuse F01, 12 V, display board or tube Internal monitor faults
No colour on an external monitor MZ-1R01 not fitted Things that are not faults
Tape does not move, or will not load Pinch roller, head, deck mechanism Cassette deck faults
File mode error at start-up Wrong file found first on the tape Things that are not faults

[2]

Normal start-up

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Know what a healthy machine does before deciding it is faulty. With no tape in the deck, the IPL opens the cassette lid and shows Make ready CMT. With the BASIC tape inserted it shows IPL is looking for a program, then IPL is loading BASIC MZ-1Z001; loading takes about two minutes and the tape rewinds at the end. With a floppy interface fitted, the IPL tries drive 1 first and asks for F (floppy) or C (cassette) if the drive is not ready; holding C at switch-on loads from tape.[3] Sharp also asks for at least 10 seconds between switching off and on again.[4]

No power

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  1. Check the mains lead and the figure-eight inlet at the back.[5]
  2. Unplug, raise the upper cabinet and check F101 (T1A) on the power supply.[2]
  3. If F101 is good, check SW101 and the transformer primary through L101. The transformer T101 has a thermal fuse in its primary; an open thermal fuse shows as an open primary.[2]
  4. If F101 has blown, look for a short on the secondary side before fitting a new one: the bridges D21 and D41, the reservoir capacitors C22, C23, C45 and C46, and the −5 V rectifier D1 with C1.[2]

No start-up

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If the machine powers up but the lid does not open and nothing appears on either monitor, measure the four rails on the supply's output connector or at CN7 on the CPU board: +5 V, +12 V, +15 V and −5 V.[2][6] This has to be done with the upper cabinet raised, which Sharp's manual warns against because of the risk of damage and electric shock;[7] keep hands and probes clear of the supply's mains side and of the display board.

  • +5 V missing: check F21 (T2.0A) and the +5 V switching regulator around IC21. If F21 has blown, look for a short on the +5 V line before replacing it.[2]
  • +12 V missing: check F41 (T2.0A) and the regulator around IC42. The display unit and the cassette deck both depend on 12 V.[2][8]
  • All rails present: check the reset circuits on the CPU board. The two switch inputs on its first sheet, BST and EXRESET, each pass through a 10 µF capacitor (C5, C4) and a 1S1555 diode network into IC1.[9] The display controller LZ90D01 runs from the 16 MHz crystal X1; check that it oscillates.[10]

Ohishi's MZ-2000 showed exactly this symptom: it seemed to be powered, but neither the cassette nor the floppy drive was accessed and nothing appeared on screen. When its power cord was pulled out during checks, the 5 V fuse blew. A new fuse did not bring it back, and he fitted a main board said to come from an MZ-2200, after which the IPL message appeared.[11]

Internal monitor faults

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The display unit takes sound, sync, video and +12 V from the CPU board, with a 2 A fuse, F01, on its 12 V input.[12][10] Because the external colour monitor is driven from the MZ-1R01 board, a fault that affects only the internal screen lies in the display unit, its cable, or the 7407 buffers (IC2) that drive the sync, video and sound lines at connector CN2 on the CPU board.[13]

  • No raster at all: check F01 and the 12 V at the display connector, then the horizontal output stage (Q2006) and the flyback transformer T2002.[12]
  • Picture rolls or tears: adjust V-hold (R2015) or H-hold (L2002) before suspecting parts.[12]
  • Picture distorted and impossible to adjust: Ohishi's internal monitor showed a stable but badly bent picture that no preset could correct. Swapping the display board for another MZ-2000's made no difference, and fitting another picture tube cured it.[11]
  • No sound: the speaker is driven by I2002 on the display board from the CPU board's sound line; check the volume knob at the back first.[12][5]

Cassette deck faults

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The deck's four keys act on its motor and eject mechanism directly, so they show whether the mechanism works independently of the computer: rewind and fast forward should each run the tape and light their lamps.[14]

  • Tape stops, slips or wraps: inspect the pinch roller. Its rubber deteriorates with age and can melt.[13][15]
  • Loads fail with the tape moving normally: clean the head; Sharp says a dirty head stops accurate recording and playback.[4]
  • Oil on or around the lid: the lid's oil damper can leak, which Ohishi describes as a trouble particular to the MZ-2000.[16]
  • Deck still fails after adjustment: on Ohishi's machine a service engineer found a broken shaft on the deck chassis, and the chassis was replaced.[16]
  • Solenoids do not pull in: the play, fast-forward, rewind and lid solenoids are driven by the TD62003 driver IC1 on the cassette control board, which also needs 12 V and 15 V.[17]

Graphics faults

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Graphics need the MZ-1R01 board, fitted above the CPU board; each further page is a set of eight 16 Kbit dynamic RAMs plugged into its sockets.[18] The board takes +12 V, +5 V and −5 V from the CPU board through CN6, so check all three if graphics fail.[6]

Things that are not faults

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  • No colour on an external monitor without the MZ-1R01: the colour output chip is on that board.[13]
  • Reverse video appears on the internal green screen but not on a colour monitor.[13]
  • File mode error at start-up: the IPL loads the first program file it finds and stops with this message if it meets a different kind of file first.[3]
  • The lid opens on its own at switch-on: that is the IPL asking for a tape.[3]
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References

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  1. ↑ Sharp, MZ-2000 Owner's Manual (Japanese) (File:Sharp MZ-2000 Owner's Manual.pdf), section 4.4, circuit diagrams, printed pages 62 to 76 (PDF pages 63 to 77).
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Sharp, MZ-2000 Owner's Manual (File:Sharp MZ-2000 Owner's Manual.pdf), figure 4-18, power circuit (unit DBOXD0044PAZZ), printed page 70 (PDF page 71); also File:Sharp MZ-2000 power supply circuit (owner's manual).png: SO101, double-pole switch SW101, fuse F101 (T1A), line filter L101, transformer T101 (P0079PA) with thermal fuse T.F; +5 V switching regulator TL494CN IC21 with bridge D21 (S4VB10), fuse F21 (T2.0A), C22 and C23 (2200 µF 25 V), Q21 (A770Y), Q22 (A673C), L21, D22 (CTB24), C25 (4700 µF 10 V) and VR21 (1 kΩ); +12 V switching regulator TL494CN IC42 with bridge D41 (S4VB10), fuse F41 (T2.0A), C45 and C46 (2200 µF 35 V), Q41 (A770Y), Q42 (A673C), L41, D42 (CTB24), C48 (3300 µF 16 V) and VR41 (1 kΩ); +15 V from IC41 (µPC7815H or TA78015AP); −5 V from FR1, D1 (V03C), C1 (470 µF 16 V) and IC1 (µPC7805H or TA78005AP); outputs +15 V, +12 V, GND and +5 V, with −5 V on its own lead.
  3. ↑ 3.0 3.1 3.2 Sharp, MZ-2000 Owner's Manual (File:Sharp MZ-2000 Owner's Manual.pdf), section 2.1, initial program loading, printed pages 15 to 18 (PDF pages 16 to 19): "Make ready CMT" with the lid opened when no tape is set; "IPL is looking for a program" and "IPL is loading BASIC MZ-1Z001"; about two minutes to load BASIC, tape rewound at the end; disk priority with a floppy interface fitted; C held at switch-on for tape; F or C asked for if drive 1 is not ready, then a drive number; BREAK during a tape load rewinds the tape, and C restarts the search; the IPL loads the first file of mode OBJ it finds and reports "File mode error" for any other type.
  4. ↑ 4.0 4.1 Sharp, MZ-2000 Owner's Manual (File:Sharp MZ-2000 Owner's Manual.pdf), appendix A.4, handling precautions, printed pages 151 and 152 (PDF pages 152 and 153): leave at least 10 seconds between switching off and on, and do not plug in with the switch on; clean the cassette heads once a month; turn the rear brightness control down for long sessions to avoid screen burn; do not use or store the machine with the upper cabinet open.
  5. ↑ 5.0 5.1 MZ-80Bがグレードアップして登場！シャープの一体型PC「MZ-2000」– Sasaki Jun, AKIBA PC Hotline! (Impress), 13 April 2021—link(accessed 2026-10-21) Rear panel: figure-eight mains inlet with the power switch above it; RESET and IPL buttons, volume and brightness knobs, DIN 8-pin colour monitor socket.
  6. ↑ 6.0 6.1 Sharp, MZ-2000 Owner's Manual (File:Sharp MZ-2000 Owner's Manual.pdf), figure 4-15, CPU board (5), printed page 67 (PDF page 68): CPU board power connector CN7 with −5 V, +12 V, +5 V and GND, decoupled by C31, C32 and C33 (100 µF 16 V); connector CN6 to the MZ-1R01 carrying +12 V, +5 V and −5 V.
  7. ↑ Sharp, MZ-2000 Owner's Manual (File:Sharp MZ-2000 Owner's Manual.pdf), section 3.1, printed pages 36 and 37 (PDF pages 37 and 38): switch off and unplug, remove the two fixing screws under the keyboard, lift the upper part from the front and hold it on the support arm; do not switch on with it raised.
  8. ↑ Sharp, MZ-2000 Owner's Manual (File:Sharp MZ-2000 Owner's Manual.pdf), appendix A.3, printed pages 149 and 150 (PDF pages 150 and 151): display unit DC 12 V ±10 %, 1.05 A (1.2 A maximum); cassette deck rated 5 V ±5 %, 12 V ±5 % (regulated) and 15 V (unregulated), with a 12 V electronic-governor motor; power supply outputs 5 V, −5 V, 12 V and 15 V.
  9. ↑ Sharp, MZ-2000 Owner's Manual (File:Sharp MZ-2000 Owner's Manual.pdf), figure 4-11, CPU board (1), printed page 63 (PDF page 64): the BST and EXRESET switch inputs each pass through a network of a 10 kΩ resistor, a 10 µF 16 V capacitor (C5, C4), a 0.1 µF capacitor and a 1S1555 diode to a gate of IC1, feeding the LZ90D02 memory controller (IC16).
  10. ↑ 10.0 10.1 Sharp, MZ-2000 Owner's Manual (File:Sharp MZ-2000 Owner's Manual.pdf), figure 4-12, CPU board (2), printed page 64 (PDF page 65): 16 MHz crystal X1 with IC20 (40H004) clocking IC21 (LZ90D01); video RAM IC17 (TMM-2016-1); character ROM IC14; display connector CN2 with SOUND, SYNC, VIDEO, GND and +12 V, the signal lines driven by 7407 buffers (IC2).
  11. ↑ 11.0 11.1 MZ-2000モニタ交換計画, Nibbles lab. (Ohishi)—link(accessed 2026-10-21) Owner's account (from 1998): the MZ-2000 seemed powered but did not start, with no cassette or floppy access and nothing on screen; the power cord came out and the 5 V fuse blew; a new fuse did not cure it; a main board said to have come from an MZ-2200 was fitted and the IPL message then appeared, distorted on the internal monitor while an external colour monitor was normal; according to the manual only 12 V is wired to the CRT; the supply's capacitors were not bulging and are glued down; the CRT board adjustments did not restore the picture; changing the CRT board for another MZ-2000's did not help, so the tube itself was worn; fitting a good tube cured it; disconnecting the lead on the side of the tube and soldering the board's earth wire need some care.
  12. ↑ 12.0 12.1 12.2 12.3 Sharp, MZ-2000 Owner's Manual (File:Sharp MZ-2000 Owner's Manual.pdf), figure 4-16, CRT display control, printed page 68 (PDF page 69): input connector with sound input, sync, video, GND, E and +12 V; fuse F01 (2 A) on the +12 V input with C2004 (4700 µF 16 V); vertical IC I2001 (RH-IX0015TA); horizontal oscillator and driver around Q2004, Q2005 and transformer T2001; horizontal output transistor Q2006 (2SC681A); flyback transformer T2002 (RTRNF2015TA); tube 2728B31; audio IC I2002 (RH-IX0243PA) and 32 Ω speaker; presets for contrast (R2002), brightness (R2008), V-hold (R2015), V-size (R2025), V-lin (R2019), H-hold (L2002) and focus (R2047).
  13. ↑ 13.0 13.1 13.2 13.3 MZ-2000, Wikipedia (Japanese)—link(accessed 2026-10-21) The chip that produces colour output is on the first graphics VRAM board (MZ-1R01), so without it there is no colour output at all, even for text; reverse video works on the green display but is ignored on a colour display; the cassette deck's pinch roller material does not age well and the rubber can melt.
  14. ↑ Sharp, MZ-2000 Owner's Manual (File:Sharp MZ-2000 Owner's Manual.pdf), section 2.2.5, printed page 30 (PDF page 31): REW and FF (each lights an LED), STOP and EJECT act directly on the motor control and eject mechanism and work whatever the computer's mode; READ lamp green, WRITE lamp red.
  15. ↑ MZ-80B/2000エミュレータ関係, 気まぐれページ (Takky)—link(accessed 2026-10-21) The author's MZ-2000 was put away after the tape pinch roller melted.
  16. ↑ 16.0 16.1 MZ-2000, Nibbles lab. シャープ博物館 (Ohishi)—link(accessed 2026-10-21) Owner's page: a service engineer got the deck working by adjustment, then found that a shaft on the deck chassis had broken, and the chassis was replaced; oil leaking from the cassette lid's oil damper is one of the troubles particular to the MZ-2000; the owner replaced the damper and fitted the lid from an MZ-1T01.
  17. ↑ Sharp, MZ-2000 Owner's Manual (File:Sharp MZ-2000 Owner's Manual.pdf), figure 4-17, cassette tape deck control, printed page 69 (PDF page 70): controller IC7 (TC9121P); TD62003 driver IC1 for the play, fast-forward, rewind and open solenoids; LS123 one-shots IC2; LM324 read amplifier IC6; supply inputs 15 V, 12 V, 5 V and GND.
  18. ↑ Sharp, MZ-2000 Owner's Manual (File:Sharp MZ-2000 Owner's Manual.pdf), appendix A.3, printed page 149 (PDF page 150): colour graphics board (option) with the LZ90D03 controller and eight 16 Kbit RAMs (16 KB) per page, up to 48 KB, pages 2 and 3 optional.


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