Sharp MZ-6500 General Maintenance
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Routine work on the Sharp MZ-6500 centres on the power supply in the system unit, its fan, the clock's backup battery and the system DIP switch. The only service manual found is Sharp's manual for the MZ-5600, the export version of the MZ-6500, so the component references and values here are for the MZ-5600; Japanese MZ-6500 sets were built for the Japanese mains supply and may differ in places.[1][2]
Safety
[edit | edit source]Warning: the power supply board carries mains voltage on its primary side whenever the machine is plugged in.
On the MZ-5600 the primary side has the power switch, fuse F1 (3.15 A on 120 V sets, 2.0 A on 200 V sets), a line filter with a 0.1 µF capacitor and two 2200 pF capacitors to earth, and the power transformer, which has a 130 °C thermal fuse in its winding.[3][4] The −12 V output has no overcurrent protection, and Sharp warns that shorting it can burn out the fuse resistor or damage the output transistor.[5]
Working on the power supply
[edit | edit source]Sharp's hints for the MZ-5600 supply:[6]
- Before removing the board, look it over for open wires, poor contacts, bad solder joints and burnt resistors.
- Unplug CN5, the secondary input from the transformer (V1, V2), and check the transformer's primary side.
- If the board has to come out, keep the jumper JP-1 between the boards intact and handle the insulation sheet with care.
- On reassembly, tighten the screws that hold components to the chassis to 4 kgf·cm and the others to 6 kgf·cm.
Sharp's own bench work uses an oscilloscope, a variable transformer, a voltmeter, an ammeter and a dummy load or the CPU unit.[6]
Adjustments
[edit | edit source]| Preset | Sets | Target |
|---|---|---|
| VR1 | +5 V output | 5 V ± 0.02 V |
| VR2 | +12 V output | 12 V ± 0.05 V |
| VR4 | +5 V current limit | 9.2 A ± 0.2 A |
| VR3 | ALARM timing | 5 ms before the +5 V falls |
[7] Turning VR1 or VR2 clockwise raises the voltage. Sharp says not to touch VR5.[7] The 9.2 A current setting for VR4 is lower than the 10.8 A rating given in the technical reference for the MZ-5631, MZ-5641 and MZ-5645 supply.[5]
Connectors
[edit | edit source]| Connector | Pins |
|---|---|
| CN1 (CPU board) | 1 −12 V, 2 +12 V, 3 and 4 +5 V, 5 ALARM, 6 to 8 0 V |
| CN2, CN3 (drives) | 1 +12 V, 2 and 3 0 V, 4 +5 V |
| CN4 | 1 0 V, 2 +12 V |
| CN5 (from the transformer) | 1 and 2 V1, 3 and 4 V2 |
Overload
[edit | edit source]The +5 V and +12 V outputs shut down on overload. If the supply does not come back after the fault is cleared, switch off, wait 30 to 40 seconds and switch on again; if it still does not start, a fuse may have opened.[5]
Fan
[edit | edit source]The power supply unit has its own DC fan.[4][3] Check that it turns whenever the machine is on.
Clock backup battery
[edit | edit source]The real-time clock (RP5C01) keeps time and its 13 bytes of RAM from a backup battery that is recharged while the machine is on. The MZ-5600 parts list gives the battery only as a Sharp part number, UBATN1001ACZZ, without its type.[8][9] Inspect the battery and the board round it for leakage whenever the case is open. Sharp's diagnostic program includes a battery backup test.[10]
System DIP switch
[edit | edit source]The system DIP switch is on the bottom of the system unit. Section 2 starts the built-in self check when it is set to ON with the machine switched off; set it back to OFF when the check is finished.[11]
Maintenance checklist
[edit | edit source]- Check the supply fan turns.
- Measure +5 V, +12 V and −12 V at the connectors, and trim VR1 and VR2 only if they are outside Sharp's limits.
- Inspect the clock backup battery for leakage.
- Run the self check (DIP switch section 2) and return the switch to OFF.
- Inspect the electrolytic capacitors listed in the Sharp MZ-6500 Capacitor Replacement Guide.
Related pages
[edit | edit source]- Sharp MZ-6500
- Sharp MZ-6500 Troubleshooting Guide
- Sharp MZ-6500 Capacitor Replacement Guide
- Sharp MZ-5600 Service Manual
References
[edit | edit source]- ↑ Sharp Corporation, Service Manual, Personal Computer Model MZ-5600 (code 00ZMZ5600SM/E). Hosted as File:Sharp MZ-5600 Service Manual.pdf; description at Sharp MZ-5600 Service Manual.
- ↑ MZ (コンピュータ), Wikipedia (Japanese)—link(accessed 2026-10-21) MZ-5600: the overseas model of the MZ-6500.
- ↑ 3.0 3.1 3.2 Sharp, MZ-5600 service manual, power supply board circuit, PDF page 107; also hosted as File:Sharp MZ-5600 power supply circuit (service manual).png. Primary: SW, F1 3.15 A/2.0 A (120 V series/200 V series), noise filter NF, C1 0.1 µF, C2 2200 pF × 2 to earth, CN2, transformer TR with a T130 °C thermal fuse; secondary windings S1 and S2 to CN5 of the P/S unit; fan. Secondary: RC1 and RC2 bridges, C3 10,000 µF 50 V, M1 and M2 controllers, F1 130 °C thermal fuse with R3, VR1 (+5 V adjust), VR2 (+12 V adjust), VR4 (+5 V current adjust), VR3 (ALARM); connectors CN1 (1 −12 V, 2 +12 V, 3 and 4 +5 V, 5 ALARM, 6 to 8 0 V), CN2 and CN3 (1 +12 V, 2 and 3 0 V, 4 +5 V), CN4 (1 0 V, 2 +12 V), CN5 (1 and 2 V1, 3 and 4 V2); values written for the 120 V and 200 V series.
- ↑ 4.0 4.1 Sharp, MZ-5600 service manual, parts list "Power supply (PRI.) unit", PDF page 132: power supply primary unit (200 V); seesaw switch; power transformer RTRNP1004ACZZ; DC fan NFANP1006ACZZ; fuse 250 V 2 A with holder; capacitor for line bypass (2200 pF); coil; capacitor 250 V 0.1 µF; AC socket; AC switch panel.
- ↑ 5.0 5.1 5.2 Sharp Corporation, MZ-5500/5600 Technical Reference Vol. 2 (Hardware) (File:Sharp MZ-5500 and MZ-5600 Technical Reference Vol. 2.pdf), section 16, "Power supply unit", PDF pages 109 and 110: MZ-5631, MZ-5641 and MZ-5645 supply, +5 V 10.8 A, +12 V 3.9 A, −12 V 0.15 A; CPU connector pin 1 −12 V (blue), 2 +12 V (yellow), 3 and 4 +5 V (red), 5 ALARM (orange), GND (black); overcurrent protection on +5 V and +12 V: if the unit does not recover after the cause is removed, switch off, wait 30 to 40 seconds and switch on again, and if power still does not come on a fuse may be open; −12 V has no overcurrent protection and a short may burn out the fuse resistor or damage the output stage transistor.
- ↑ 6.0 6.1 Sharp, MZ-5600 service manual, section 16-3, "Troubleshootings", (1) "Hints and tips", printed page 81 (PDF page 82): do not try to remove the printed board at first; look for open wires, contact failures, poor soldering and burnt resistors; unplug the power input connector (V1, V2: CN5) and check for a fault on the primary side of the power transformer; when removing the board, tighten screws holding components to the chassis to 4 kgf·cm and other screws to 6 kgf·cm, take care not to open the jumper JP-1 between the boards, and handle the insulation sheet with care; tools: oscilloscope, 200 V AC variable transformer (Slidac), voltmeter (1 to 50 V AC/DC), ammeter (0.1 to 15 A AC/DC), dummy load or CPU unit, power supply transformer.
- ↑ 7.0 7.1 Sharp, MZ-5600 service manual, section 16-2 (7), "Adjustments", printed page 81 (PDF page 82): VR1 +5 V voltage adjustment, 5 V ± 0.02 V; VR2 +12 V voltage adjustment, +12 V ± 0.05 V; VR4 +5 V output current adjustment, 9.2 A ± 0.2 A; VR3 ALARM adjustment, 5 ms faster than the 5 V falling edge. Troubleshooting steps 5-1, 7-1 and 9-2 (printed pages 82 and 83): clockwise turns of VR1 and VR2 raise the voltages; clockwise turns of VR3 shorten the time between AC input off and ALARM; do not adjust VR5.
- ↑ Sharp, MZ-5500/5600 technical reference (File:Sharp MZ-5500 and MZ-5600 Technical Reference Vol. 2.pdf), section 13, "RTC (Real Time Clock)": with power on, +5 V is supplied to the RP5C01 and the backup battery is recharged; at power-off the backup battery keeps the time and the internal RAM.
- ↑ Sharp, MZ-5600 service manual, parts list "CPU PWB unit", PDF page 125: item 39 battery UBATN1001ACZZ; crystals 32 kHz, 14.7456 MHz and 24 MHz.
- ↑ Sharp Corporation, Diagnostic Manual for Model MZ5600A (File:Sharp MZ-5600A Diagnostic Manual.pdf), contents and section III, "RTC battery backup test (service check program 11)".
- ↑ Sharp, MZ-5600 service manual, section 17-2, "Check procedures", printed page 84 (PDF page 85): set section 2 of the system DIP switch, located on the bottom of the System Unit, to ON with the System Unit turned off; when all checks are completed, turn off the system and set section 2 back to OFF.