Mitsubishi ML-F80 General Maintenance
The Mitsubishi ML-F80 is a one-piece MSX1 computer from 1984 with its keyboard and mains supply in the case and two cartridge slots, one on top and one at the rear.[1] No service manual for it has been found, so the checks below rest on the MSX standard, the rating label and a photograph of the main board.
Mains supply
[edit | edit source]The ML-F80 is rated at 220 to 240 V, 50/60 Hz, 27 W.[2] The supply is inside the case, so the power cord, switch and transformer carry mains voltage. Unplug the computer before opening it, and keep clear of the supply area if it has to run with the cover off.
Opening the case
[edit | edit source]No disassembly procedure has been published for the ML-F80. Photograph every screw position and connector before removing it, and note how the keyboard and the video and RF board are joined to the main board.[3] The main board carries a printed "STATIC PREVENT DISCHARGE" warning; work on an earthed mat or wear a wrist strap.[3]
Cartridge slots
[edit | edit source]Both slots are standard MSX cartridge connectors. Clean the contacts with isopropyl alcohol on a lint-free swab, and clean each cartridge's edge connector before blaming a slot. Insert and remove cartridges with the power off.
The slots are also the easiest place to measure the supply. The MSX 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 the +5 V supply to give 300 mA per slot and the ±12 V supplies 50 mA for all slots together.[4]
| Pin | Signal |
|---|---|
| 41, 43 | Ground |
| 45, 47 | +5 V |
| 48 | +12 V |
| 50 | −12 V |
The video RAM is eight NEC D416C-2 chips, and the µPD416 type also needs −5 V, which is not on the slot. Measure it at pin 1 of one of those chips, against pin 16.[3][5]
Joystick ports
[edit | edit source]The two general ports follow the MSX standard, with +5 V on pin 5 rated at 50 mA.[6] Several controllers made for other machines use the same 9-pin connector with different wiring and can short the +5 V supply or damage pin 8; the MSX Resource Center lists the Amiga mouse, Atari and Commodore paddles and Sega Master System pads among them.[6] Check the wiring of any controller not made for MSX against the MSX pinout before plugging it in.
Video
[edit | edit source]The British ML-F80 gives composite video and PAL RF; the French model gives RGB on a DIN socket instead.[1] The video and RF circuits are on their own small board.[3]
Capacitors
[edit | edit source]Advice on the MSX Resource Center forum is to replace the main supply's electrolytic capacitors whatever their condition and to judge the others by the picture and sound.[7] See the Mitsubishi ML-F80 Capacitor Replacement Guide.
Related pages
[edit | edit source]- Mitsubishi ML-F80
- Mitsubishi ML-F80 Troubleshooting Guide
- Mitsubishi ML-F80 Capacitor Replacement Guide
- Recommended Tools
References
[edit | edit source]- ↑ 1.0 1.1 Mitsubishi ML-F80, MSX Resource Center wiki, 7 March 2026—link(accessed 2026-10-21) One unit; two cartridge slots, top and rear; UK version with RF and composite video, French version with RGB on a DIN socket; printer port, cassette, two general ports; 64 KB RAM, TMS9929A, AY-3-8910A, D780C-1.
- ↑ File:Mitsubishi ML-F80 rating label.jpg, rating label: Volts 220-240V~, Hertz 50/60Hz, Watts 27W, Mitsubishi Electric Corporation, Made in Japan.
- ↑ 3.0 3.1 3.2 3.3 File:Mitsubishi ML-F80 main board.jpg, photograph of an ML-F80 main board uploaded to the MSX Resource Center wiki by Mars2000you on 7 April 2020: main board J0510425K with a separate video and RF board (55-4007D) joined to it by wires and plug-in connectors; two keyboard connectors marked KEY; cartridge connectors CN1 and CN2; a relay RL beside the cassette and joystick sockets; a "STATIC PREVENT DISCHARGE" marking on the main board.
- ↑ MSX Cartridge slot, MSX Resource Center wiki, 6 July 2026—link(accessed 2026-10-21) Pinout of the standard MSX cartridge slot: 41 and 43 GND, 42 CLOCK (3.579545 MHz), 44 SW1, 45 and 47 +5 V, 46 SW2, 48 +12 V, 49 SOUNDIN, 50 −12 V; the +5 V supply must handle up to 300 mA per slot and the ±12 V supplies up to 50 mA for all slots.
- ↑ Matsushita, Service Manual: Personal Computer CF-2700 (IED84113035C2), printed page 9, Fig. 7: µPD416C video RAMs with +5 V on pin 9, +12 V on pin 8, −5 V on pin 1 and ground on pin 16. See Panasonic CF-2700 Service Manual.
- ↑ 6.0 6.1 General Purpose port, MSX Resource Center wiki, 13 December 2025—link(accessed 2026-10-21) MSX general purpose (joystick) port: pins 1 to 4 inputs, pin 5 +5 V (50 mA), pins 6 and 7 bidirectional open collector, pin 8 output, pin 9 ground. Devices that can cause damage when plugged in directly: an Amiga mouse (pin 5 is a button on the Amiga, so pressing it shorts +5 V), Atari and Commodore paddles (short +5 V through the second button or the potentiometers), the FM Towns Marty pad and Sega SG-1000, Mark III and Master System pads (a button on pins 8 and 9 can damage pin 8), and RS-232C serial devices.
- ↑ Recap recommendations, June 2018—link(accessed 2026-10-21) RetroTechie, 23 June 2018: the main power supply capacitors in an MSX are worth replacing whatever their condition; those in the audio and video circuits show their condition in the output; bypass capacitors round the board can often be removed without the machine stopping; replace them one at a time.
