Mitsubishi mp 286L Help: Learn How to Fix It Yourself.

Author: Rando_GUY

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History and Diagnostics

General History

"At last, a laptop computer that doesn't compromise on readability, speed, power or expandability for the sake of portability. The mp286L has the largest, brightest display available on any laptop. Its backlit LCD display can be read from several feet away in virtually any light. The mp286L is so remarkable that once you've started to use it, you may never want to return to a desktop computer again!"

-Commercial retail box advertisement, 1988

We know Mitsubishi often for their cars, but they're also known to produce quite a lot more than that. pencil lead, forklifts, air conditioners, even naval ships and fighter planes at some point. But very few people know about the Mitsubishi mp286L, which, while it isn't their first consumer computer they made (they first created MSX home computers), stands as their first entry into the business computer market.

Their entrance into the business was poorly timed however, as its release in 1988 was placed in the middle of the technological advancement to faster, tougher hard drives and RAM, alongside the advent of the more reliable medium of CDs. This, on top of the already stiff competition, left their hard drive manufacturers, Miniscribe, to engage in a scandalous operation out of desperation to keep up with business, which ended in their bankruptcy and their acquisition by Maxtor, cutting Mitsubishi's assembly lines short.

Before anyone knew it, they grew outdated in the following of the 90's, and have fallen into heavy obscurity since.

Like all laptops of the era, this one has a low capacity hard drive, an HD 3.5" floppy drive, uses old serial and parallel communication, and just being very heavy to carry.

everything is inside a dark gray, hard plastic casing with a sleek finish. The bulky clam-shell display is slightly curved at the top, while the bottom and the sides are mostly flat, creating a very box-like shape. All edges and corners are rounded. Coming off the front of the closed unit is a handle that click in and out.

Since Mitsubishi decided to have and emphasis on portability, there is no battery in the machines for reduced weight. this means you have to have it plugged into an outlet at all times to use it, making on-the-go use less convenient.

They also made some bizarre changes to the standard keyboard arrangement, making the function and arrow keys half-sized horizontally, and rearranging them so that the arrow keys are in the top right corner, and the last 4 function keys placed above the first 4, across from the arrow keys, making them easy to miss, and more-often-than-not awkward to use.

Due to the brevity of these computers, alongside their strange form factors, it proved to be incredibly difficult to find any information on these lap crushers. So, for archival purposes, I took it upon myself to create this ifixit page dedicated to these machines, so that anything, and everything that can be found on these things can be placed here for all to see. Any and all useful additions are welcome!

*both distributed and manufactured by Mitsubishi Electric (Disks Monitors)

Brand: Mitsubishi
Series: MAXY portable (IBM compatible(see Software Things for details))

Model Numbers:

210 (with dual floppy 3.5" drives
220 (1 floppy drive, 1 hard drive)
240EVP (with an EGA screen)
MP-2120* (*I have this one, same as 220)
MP-2130

Weight: ~10-16 lb (4.5-7.2 kg)

Original Price Range: From 5400$

can range from 1400-5000$

Size: (WxHxD) 12.3" x 3.5" x 14.2"

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Processor: Intel 80286

Clock rates: 5, 6, 8/12 (standard), 16*, 20*, 25MHz* (*later models released by Fujitsu and AMD)
Processing power: 6-12MHz (1 wait state for anything above 8MHz)
- works with an optional Intel 80287 math co-processor

Memory: 640 kb of RAM

expandable to 2.6 mb with proprietary memory card (more info to be found on it)

Power:

* Whole power supply unit:

Model No.: PC21WA (Power supply circuit type by model no. is TBD)
- Voltage needed: 115V, 220V-*240V (*230V is the factory setting)
- Power Cable: Standard IEC AC power cable within the above voltages
CMOS: Proprietary Varta Ni-Cd battery (Be sure to remove that)
- Volts & Amps: 3.6v, 170mAh

Built-in Storage: Miniscribe Hard Drive* (*Check links in the references for pictures)

No. of drive types: 0-47 (this is shown and requested in the setup disk software)
Model No. : M8425* (*often shortened to just 8425)
- interface: ST506
- Recording methods: MFM, SCSI* (*uses a different controller card, likely 3rd party)
- Capacity: 20-21MB
  - Can go up to 40MB
- Phase: DTF
- Platter size: 3.5"
- No. of Heads: 4
- No. of Cylinders: 615

Internal Floppy drive: 3.5"

Disk capacities: 720 kb (standard), 1.44 mb (High Density)
- It's one or the other when comparing units

Sound: 1x 15 mm x 2 mm Piezo speaker plate

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I/O: all of these are connected to the main computer board by 4 proprietary card slots

Serial ports: 2x male-end 9-pins (RS-232C)
CRT Display out: 1x female-end 9-pin (likely serial communication)
- Can connect to an external 16-color CRT display
Network Inputs: 1x line, 1x telephone jacks (Both shaped like RJ45, not RJ11)
- works with an optional 2400 bps modem which can be installed inside the machine (They even give an installation guide!)
External drive: 1x 26-pin floppy drive* (*female port end)
- connects with 5.25" 1.2mb or extra 3.5" 1.44mb floppy drive
- Cable Pinout
External input device: Female bus port end (for number pad mentioned in Included Software section)
Printer Cable: 1x Centronics 25-pin parallel
Back-Switches*: 2x arrays of 4 switches (for small, temporary changes after set up)
- DTS-4 to the left of FDD port (if looking from the back)
- DPS-4 to the right of CRT port (if looking from the back)
  - 6 levers present by CRT on MP-2130 Model (why it's different is unknown)

Keyboard:

No. of keys: 86/101*
- only w/ aforementioned number pad
Key layout: Custom AT
Design: Mechanical alps switches

Display:

Type: back-lit cold CRT, passive-matrix neutral 'supertwist' nematic LCD
- Knobs and switch on bottom right corner of front bezel control back light and blacks-on-whites contrast configuration
Dimensions: (WxH) 9" x 6.5", 11.5" diagonal
Pixel Resolution: 640 x 200-400, for graphics and text respectively
Character resolution: 80 characters/line
compatible aspect ratios: EGA and CGA
- Some documentation mentions a unique 'Hercules' resolution mode. More information on that soon...

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Included In-Box Software:

Setup & diagnostics (for any pre-POST configurations)
utilities (for mouse and/or number pad, as well as dial-up connection and system checkup)
MS-DOS 3.30 driver
WordPerfect (circa 1990, "For IBM Personal Computers")
- Some units are found with a Cheat sheet for keyboard shortcuts (likely for office/school use)

BIOS: Phoenix 80286/80386 ROM BIOS version 3.10 (IBM BIOS clone)