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Radio Shack DMP-100
Radio Shack LP VII


Seikosha/Axiom GP-100 (Ribbon: GP-20050)

Other printers based on the same engine

  • Seikosha/Axiom GP100TI II (TI-99/4a) / GP-100AT (Atari)
  • C. Itoh Riteman C+ F+ F+11, Prowriter Jr. Jr+, CI 6024
  • Gorilla Banana
  • Leading Edge GX-100
  • Commodore VIC 1525
  • Alps ASP 1000 / 1600 / PTSWA 10
  • Amstrad DMP2000 / DMP2160 / DMP3000 / DMP3000D / DMP3160
  • Spectravideo SV-901 / SVI-901


Other possible printer or ribbon matches

Not sure about these.

C. Itoh Gx100
Seikosha/Axiom GP-80 (ribbon GP-08050)
Commodore VIC 1515 (GP-80 vs GP-100?)
Seikosha/Axiom GP-250X
Alpha Matrix 2100

Manuals and other info

Re-inking an old ribbon

You can re-ink old impact ribbons with oil-based stamp pad ink.

"Stamp pad ink" comes in both water(glycerine)-based, and oil-based versions. Make sure to get oil-based.

Original dot-matrix ink was oil-based because, aside from not drying out, the oil in the ink was necessary to lubricate the pins in the print head.

C. Itoh ribbon hack

Photos of C. Itoh ribbon to DMP-100 hack:

Preparing the ribbon:

When you buy the ribbons new, they have some clips formed into them that don't fit the DMP-100.
Shave all clips and bumps off to make the bottom and sides flat. You don’t have to modify the tops. The plastic is soft enough that it's not too hard. I use a multitool to break most parts off by grabbing them with the pliers, then clean up a little by shaving with the knife and maybe the file. The fat pin in the center of one of the housings is a bit tough to get with a knife alone, so you may have to use the saw on that.
Put about ¾ inch square of 3M automotive double stick foam tape on the bottom of each housing. Leave the red plastic film on for now.

Installing the ribbon:

Use some alcohol and paper towel to clean the top surface of the steel platforms where the normal ribbon housings go, so they are clean and dry.
Peel off the red plastic film from the housings.
Take the larger housing with the round shape and the bump on top in your Left hand, and the smaller housing with the flat blade on top in your Right hand, and stick them to the steel platforms, butted right up against the inside walls of the printer, and such that the ribbon closest to the front of the machine forms a straight line through the ribbon advance pincher behind the print head. The ribbon that touches the paper will not form a straight line. You should feel a ribbon tension spring compress a little in the right-hand housing, and the ribbon should have no slack. (route the ribbon in front of the print head and through the ribbon advance pincher the same as normal)
3m adhesive foam will stick well enough to print immediately. It will become stronger over time, but can still be peeled off (slowly) later, with no damage to the printer.