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National FS-5500 General Maintenance

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National FS-5500F2 rear panel
Rear panel: AC outlets at the left, the three expansion slot covers, and the video, audio and RF sockets at the right

The National FS-5500 is built from a main board, a video board, a ROM and RAM board, an expansion slot board, a separate power supply unit and one or two floppy drives, with a keyboard that carries its own trackball.[1] No service manual has been found. The notes below rest on Matsushita's published specifications, photographs of the boards and an owner's account of adding a second drive.

Mains supply

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The FS-5500 runs from AC 100 V ±10%, 50/60 Hz, on a Japanese two-pin plug, and has two AC 100 V outlets for a monitor.[2] One outlet follows the computer's power switch and the other is live whenever the computer is plugged in. The mains fuse, rated 125 V 3 A, is on the rear panel.[1]

  • Outside Japan, run the computer from a step-down transformer. Anything plugged into its two outlets draws through the same transformer, so size it for the monitor too.
  • The power cord, the power switch, the rear outlets, the fuse holder and the power supply unit carry mains voltage. Unplug the computer before removing the cover.

Opening the case

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No disassembly procedure has been published. Photograph each screw and connector before removing it. The power supply unit sits at one side in its own case, the video board stands at the left edge of the main board, the expansion slot board is at the rear, and the floppy drives are at the front. Ribbon cables run from the expansion slot board to the drives.[1][3] The ROM and RAM board and the video board plug into a 64-pin and a 50-pin connector on the main board.[1]

Clock and backup cell

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MSX2 machines keep the time, the date and start-up settings such as screen position, WIDTH and colours in a Ricoh RP-5C01 clock chip, which is kept running by a battery while the machine is off.[4] On the FS-5500 the RP5C01 is IC125 on the main board, and the board also carries a yellow cylindrical cell held down by a cable tie.[1][3] Check the cell and the board round it for leakage whenever the case is open; see Battery Explosion, Capacitor or Corrosion Damage. The FS-CR1008S cartridge has its own battery for its 8 KB of SRAM.[5]

Floppy drives

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For cleaning and repairing the drives, see Floppy Drive Repair.

Adding a second drive to an FS-5500F1

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The FS-5500F1 has one drive, but its controller and wiring are made for two.[5][6] One owner fitted a Y-E Data YD-646E as the second drive:

  1. Fit a 4-pin power connector to the drive if it has none. The YD-646E has the pads for one.
  2. Bridge the jumper pads marked in the owner's photograph. The pads are for a surface-mount part, so a 0 Ω chip resistor is the neatest bridge.
  3. Remove the blanking plate from the F1's second bay.
  4. The drive is lower than the bay, so raise it on 3 to 5 mm spacers.
  5. Connect the spare drive cable and the power lead.

[6]

Cartridge and expansion slots

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The two front cartridge slots are standard MSX slots with eject buttons.[5] The standard puts ground on pins 41 and 43, +5 V on pins 45 and 47, +12 V on pin 48 and −12 V on pin 50, and requires 300 mA per slot from +5 V and 50 mA from the ±12 V supplies for all slots together.[7] Clean the contacts with isopropyl alcohol on a lint-free swab, and switch off before inserting or removing a cartridge.

The three rear expansion slots carry the same signals on a different connector, so a standard cartridge needs an adapter.[2][1]

Trackball and joystick ports

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The trackball and its two buttons are wired to joystick port 1 or port 2, or switched off, by a switch on the front control panel.[5] The two joystick ports follow the MSX standard, with +5 V on pin 5 rated at 50 mA. An Amiga mouse, Atari or Commodore paddles, and Sega Master System or FM Towns Marty pads can short the supply or damage pin 8; check the wiring of any controller not made for MSX before plugging it in.[8]

Capacitors

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See the National FS-5500 Capacitor Replacement Guide.

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References

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  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 National FS-5500, USB Secret Base (up-c), 2010 to 2017—link(accessed 2026-10-21) Rear panel: switched and unswitched AC 100 V outlets, fuse (125 V 3 A), power cable, earth terminal, 21-pin RGB connector, three dedicated expansion slots. Inside: power supply unit, expansion slot board, memory board, video board, floppy drives A and B. The expansion slot board has three 50-pin slots with the standard MSX slot signals, usable with standard cartridges through a converter; 34-pin connectors CN909 and CN910 with flat cables go to the floppy drives. The real time clock (Ricoh RP5C01, IC125) is on the main board with crystal X3.
  2. ↑ 2.0 2.1 National FS-5500F2, MSX Resource Center wiki, 3 July 2026—link(accessed 2026-10-21) Power plug for the main supply (JIS C 8303 class, AC 100 V ±10%, 50/60 Hz); two power outlets for a monitor (AC 100 V); floating ground; the three rear slots have the standard slot pinout on a different connector; the lowest has an extra 20-pin connector for RAM expansion; MB8877A floppy disk controller.
  3. ↑ 3.0 3.1 MSX Resource Center wiki, File:Fs5500f1f.jpg, "National FS-5500 PCB", uploaded by Mars2000you on 13 September 2020 (the same photograph appears on USB Secret Base): main board marked DFUP0038ZA, with the video board standing at the left edge, a white multi-way power connector at the right edge, a yellow cylindrical cell held by a cable tie, a large blue electrolytic capacitor marked 16 V lying flat at the top left, and further radial electrolytics near the top edge and the right edge.
  4. ↑ Real Time Clock Programming, MSX Resource Center wiki, 17 March 2023—link(accessed 2026-10-21) MSX2 computers use the Ricoh RP-5C01 or compatible for the time and date and to store system parameters restored at switch-on (screen adjustment, WIDTH, initial colours, key click, BEEP, printer type, cassette speed); the registers are kept as long as the chip is powered by the battery.
  5. ↑ 5.0 5.1 5.2 5.3 National FS-5500F1, MSX Resource Center wiki, 3 July 2026—link(accessed 2026-10-21) The FS-5500F1 has one floppy drive, with a second (FS-FD352) possible; a front switch assigns the trackball and its two buttons to joystick port 1, port 2 or neither; firmware, software and clock data can be saved on the FS-CR1008S cartridge, which holds 8 KB of SRAM and a battery; two rear switches select the keyboard layout and enable or disable the built-in firmware.
  6. ↑ 6.0 6.1 FS-5500 FDDの増設 (adding a floppy drive to the FS-5500), USB Secret Base (up-c), 2010—link(accessed 2026-10-21) The FS-5500F1 has only one drive, but the controller and the harness are made for two, so fitting a second drive in the empty bay makes it the same as the F2. Drive used: Y-E Data YD-646E. That drive had no EI 4-pin power connector; the board has the pattern for one, so fit the connector (or a 4-pin right-angle header). Bridge the jumper position shown in the article's photograph; the author used a 0 Ω chip resistor because the pads are for surface-mount parts. Remove the F1's blanking plate and fit the drive; it is lower than the bay, so raise it on 3 to 5 mm spacers.
  7. ↑ MSX Cartridge slot, MSX Resource Center wiki, 6 July 2026—link(accessed 2026-10-21) Standard MSX cartridge slot: 41 and 43 GND, 42 CLOCK, 44 SW1, 45 and 47 +5 V, 46 SW2, 48 +12 V, 49 SOUNDIN, 50 −12 V; +5 V up to 300 mA per slot; ±12 V up to 50 mA for all slots.
  8. ↑ General Purpose port, MSX Resource Center wiki, 13 December 2025—link(accessed 2026-10-21) Pin 5 +5 V (50 mA). Devices that can cause damage: Amiga mouse (pin 5 is button 2 on the Amiga); Atari and Commodore paddles; FM Towns Marty pad and Sega SG-1000, Mark III and Master System pads (a button on pin 8); DE9 RS-232C devices.



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