Commodore MPS 801 Printer
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Commodore MPS 801 Printer
“The MPS 801 was Commodore’s answer to the growing need for affordable, reliable printing in the early 1980s. Based on the Seikosha GP-100 mechanism, it offered a great balance of price and performance for home and educational users. While it wasn’t the fastest or quietest printer on the market, its solid construction and compatibility with all Commodore 8-bit computers made it a popular choice. Many users remember the distinctive sound of the MPS 801 chugging away, printing out programs, school reports, and even simple graphics. It was a workhorse that just kept going, and many units are still operational today with minimal maintenance.” - Bob Russell, Commodore Product Manager
The Commodore MPS 801 was a dot matrix impact printer introduced in 1982 as Commodore’s first dedicated printer for their home computer line. Based on the Seikosha GP-100 mechanism, it featured a 7-pin print head capable of printing 80 columns of text at a speed of 80 characters per second. The printer used standard tractor-feed paper and featured both parallel and serial interfaces, making it compatible with the entire range of Commodore 8-bit computers including the PET, VIC-20, and Commodore 64. Its rugged construction, relatively low price point, and good print quality for the era made it one of the most popular printers in schools and homes throughout the 1980s.
Technical Specifications
Technical Specifications
- Dimensions
- 45 × 35 × 20 cm (17.7 × 13.8 × 7.9 in)
- Weight
- 7.7 kg (17 lb)
Features and Capabilities
Print Modes
- Draft Mode: 80 cps, single pass
- NLQ Mode: 40 cps, double pass
- Bold: Double strike
- Italic: 12° right slant
- Underline: Single pixel line
- Superscript/Subscript: ±3 dots
- Double Width: 40 characters/line
- Double Height: 2x normal height
Character Sets
- Standard ASCII: 96 characters
- International: 7 variations (US, UK, Germany, France, Sweden, Italy, Spain)
- Graphics: 64 user-definable characters
- Block Graphics: 32 shapes
- Bar Codes: Code 39 support
Paper Handling
- Type: Continuous form with tractor feed
- Width: 4” to 10” (adjustable)
- Thickness: 1+1 original, 1+4 copies
- Tractor: 1/2” or 1” pin feed
- Platen: 4” (10 cm) diameter
- Ribbon: Fabric, black (CBM 801421)
Models and Variants
MPS 801 (1982-1984)
- Model Number: MPS 801
- Features: Beige case, parallel interface
- Compatibility: PET, CBM, VIC-20, C64
- Known Issues: Early firmware bugs
MPS 801-S (1984-1986)
- Improvements: Added serial interface
- Changes: Updated ROM, better reliability
- Compatibility: All Commodore 8-bit
MPS 802 (1983-1985)
- Differences: 132-column version
- Features: Wider carriage, faster
- Rarity: Less common than 801
Third-Party Clones
- Seikosha GP-100: Original OEM
- Star Micronics Gemini: Compatible model
- Epson MX-80: Similar specifications
Usage and Setup
Basic Commands
OPEN 4,4,7 : REM Open printer device
PRINT#4,"HELLO" : REM Print text
PRINT#4,CHR$(147);: REM Clear printer buffer
CLOSE 4 : REM Close device
Control Codes
- CHR$(5): Enable printer
- CHR$(10): Line feed
- CHR$(13): Carriage return
- CHR$(17): Cursor down
- CHR$(145): Cursor up
- CHR$(147): Clear screen
Common POKEs (C64)
POKE 59468,7 : REM Enable upper/lower case
POKE 59412,4 : REM Set device number
POKE 59460,7 : REM Set output to printer
Technical Details
Print Head
- Pins: 7, vertical arrangement
- Dot Size: 0.3mm diameter
- Life: 30 million characters per pin
- Force: 10g per pin
- Voltage: 24V DC
Electrical Specifications
- Power Supply: Internal, switching
- Input: 100-120V or 220-240V AC, 50/60Hz
- Fuse: T1.6A/250V (slow blow)
- Noise Level: 55 dB (operation)
Interface Pinouts
Parallel (IEEE-488)
1 - DIO1
2 - DIO2
3 - DIO3
4 - DIO4
5 - EOI
6 - DAV
7 - NRFD
8 - NDAC
9 - IFC
10 - SRQ
11 - ATN
12 - SHIELD
13 - DIO5
14 - DIO6
15 - DIO7
16 - DIO8
17 - REN
18 - GND
19 - GND
20 - GND
21 - GND
22 - GND
23 - GND
24 - GND
Serial (IEC)
1 - SRQ
2 - GND
3 - ATN
4 - CLK
5 - DATA
6 - RESET
Common Issues and Solutions
Common Problems
- No Printing
- Check power and connections
- Verify device number (usually 4 or 5)
- Check ribbon installation
- Faded Print
- Replace ribbon
- Adjust print head gap
- Clean print head
- Paper Jams
- Check tractor alignment
- Ensure paper path is clear
- Adjust tension
- Stuck Print Head
- Clean and lubricate rails
- Check for obstructions
- Verify carriage belt
Maintenance
- Daily: Clean print head with alcohol
- Weekly: Lubricate rails
- Monthly: Clean platen
- As Needed: Replace ribbon, tractor belts
Hacks and Modifications
Common Mods
- USB Conversion: For modern computers
- Ink Ribbon Hack: Use standard typewriter ribbon
- LED Status Lights: Add indicator LEDs
- Sound Dampening: Reduce noise
DIY Repairs
- Print Head Replacement: Common failure point
- Power Supply Recap: Replace aging capacitors
- Tractor Belt Replacement: Common wear item
- Platen Resurfacing: Restore worn rollers
Legacy and Impact
Historical Significance
- First Commodore Printer: Set the standard
- Educational Use: In schools worldwide
- Home Computing: Made printing accessible
- Demo Scene: Used for ASCII art
Collectibility
- Value: $50-$200 depending on condition
- Rare Variants: Early parallel-only models
- Mint Condition: Boxed units with manuals
- Restoration: Popular with collectors
Modern Alternatives
- Epson LX-350: Modern equivalent
- Thermal Printers: For receipts
- USB Adapters: For original hardware
- Emulation: VICE, CCS64
Technical Documentation
Character Codes
0-31 : Control codes
32-63 : Uppercase + symbols
64-95 : Uppercase + symbols
96-127 : Lowercase + symbols
128-159: Graphics
160-191: International
192-223: Block graphics
224-255: User-defined
Sample Program
10 REM MPS 801 DEMO
20 OPEN 4,4,7
30 PRINT#4,CHR$(147);: REM CLEAR
40 PRINT#4,"COMMODORE MPS 801"
50 PRINT#4,CHR$(18);: REM REVERSE ON
60 PRINT#4,"PRINTER TEST"
70 PRINT#4,CHR$(146);: REM REVERSE OFF
80 FOR I=1 TO 10
90 PRINT#4,I;" ";
100 NEXT I
110 PRINT#4:PRINT#4
120 PRINT#4,CHR$(29);: REM ITALIC ON
130 PRINT#4,"THE QUICK BROWN FOX"
140 PRINT#4,CHR$(148);: REM ITALIC OFF
150 CLOSE 4
In Popular Culture
- Featured in 1980s computer magazines
- Appears in schools and offices in period films
- The subject of YouTube restoration videos
- Referenced in retro computing forums
Further Reading
About This Page
This page documents the technical specifications, operation, and legacy of the Commodore MPS 801 Printer. Information is based on official documentation, service manuals, and community knowledge.