Wheelwriter Adaptation Instructions

IBM/Lexmark Wheelwriter 1000 Teleprinter Adaptation

https://github.com/IBM-1620/Junior/raw/master/docs/wheelwriter-adaptation-instructions.pdf

The IBM 1620 Jr. project sponsored by the Computer History Museum is recreating the experience of

running historic software on a 1960s-era computer by bringing a real IBM 1620 console to life with a

cycle-accurate simulation running on a modern microcomputer. An integral part of the IBM 1620

console is the attached typewriter used to enter booting instructions and interact with programs. The

typewriters used on the original machines were the IBM Executive Model B and the IBM Selectric,

neither of which is practical to use for the recreation. Instead, a more recent IBM/Lexmark

Wheelwriter 1000 typewriter has been adapted by interposing a microcontroller between the

done for the IBM 1620 Jr. project. These instructions may work with other model Wheelwriters, but

that has not been verified. The tasks include drilling holes in the typewriter case to mount the added

USB Interface Board and USB-B cable; unsoldering two keyboard cable connectors from the

typewriter’s logic board to reuse on the interface board and be replaced by more readily available

connectors; building the USB Interface Board; and installing the interface board and cables connecting

it to the logic board. The following block diagram shows the adaptation.

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1. Pull the paper release and paper bail load levers forward.

from the top half of the case, then feed it back through the hole so

the top half is completely free.

4. Remove the ribbon cartridge by pushing on the blue lever and

then lifting up and out, then manually push the carriage all the

way to the right so it is out of the way.

5. Remove the keyboard from its

mounting by releasing four latches

along the back edge of the

keyboard and then rotating upward

slightly and pulling the keyboard

connectors where you pull on the clamp tabs to release the cable.

All the other connectors lift straight up, but the 8-wire cable J15A

is quite stiff and requires some force to lift. The black two-wire

cable going to J3 needs to be slipped out from under the clip in

the base and rerouted since the USB Interface Board will cover

that clip.

7. Remove the logic board by releasing three latches along the back

edge and lifting it out of the catches at the front.

8. Unplug the connectors from the two servo motors at the back of

the case (for platen rotation and carriage motion).

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round object such as a center punch or pencil between the two

layers of the carriage FFC cable where it makes a 90° bend in

order to slip the cable out from under the inner clip at that corner,

then slide the cable out from under the outer clip.

11. Remove the whole frame assembly by releasing the four clips at

the corners of the frame assembly. Use a twisting motion with a

large screwdriver on the inside of the sheet metal frame members

(except the right rear which is outside) to pry the latches free from

the slots in the frame while lifting the frame to completely

remove it. The latch has to bend back more than 1/8” before it is

Interface Board will go, located 1.35" from the floor of the

Wheelwriter case and centered in the width of each post.

Marking the location on a piece of masking tape and center-

punching with an awl may help. Drill only through the near

surface of the post which is less than 1/8” thick. Snap the power

supply back into place and slip its cable back under the clips in

the base.

13. Slip the platen motor cable that runs along the left side of the base

out from under its clips where it crosses the location where the

USB Interface Board will go in the middle of the base, and fold it back out of the way.

Interface Template against the reference points indicated by

arrows, and tape in place. Center-punch for the four USB

Interface Board mounting holes indicated on the template. Some

generations of the Wheelwriter 1000 have a thin aluminum static shield covering the base which

is not present on the unit in these photographs, but the procedure is the same. Drill 1/8"

mounting holes from the top.

16. From the underside of the case, countersink the four mounting holes for the USB Interface

Board standoffs so the flat-head screws will be below the surface.

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knockout panel in the rear of the lower case (on the right as

viewed from the rear). Use an awl to center-punch for the

mounting screw holes and holes at the corners and midpoints of

the center cutout area, then drill 1/8" holes for the mounting

screws, corners and midpoints. Clear out the cutout with snips,

20. Set the frame assembly loosely back in position making sure not

to pinch any cables.

21. Connect the two wires to the tabs on the switch at the bottom of

the paper bail load lever. It does not matter which wire goes to which tab.

22. Slide the carriage FFC cable back into the corner clips so the bottom layer is under the inner

corner clip and then the fold slides into the outer corner clip. Then insert the round object to

bow up the upper layer to get it uder the inner corner clip. Also slide the cable back under the

clip in the center of its track.

23. Push the frame assembly back down into its four corner latches.

24. Plug in the cables for the two servo motors at the back.

most easily done with a vacuum desoldering tool, but may also be

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4. Install a 22-27-2031 3-pin Molex connector in J9 on logic board,

with the latch away from the edge of the board.

1. Cut the VIN - VUSB trace on the underside of the Teensy board.

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4. Install the USB Interface Board onto standoffs with washers and nuts. Finish tightening using a

5. Where the FFC interconnect cables come up from under the USB Interface Board by the logic

board, pull the cables taut and fold them away from the USB Interface Board right at the

6. Install the new power cable from the logic board to the USB

Interface Board, routing it underneath all the other cables along

the back edge of the logic board. Bend the wires down sharply at

the connector on the USB Interface Board to avoid interference

7. Lay the keyboard loosely over its position and insert the FFC

cables from the keyboard into the connectors on the USB

Interface Board (this is not easy – it may require padded forceps).

8. Make a bracket to depress the keyboard FFC cables by manually

bending steel coat-hanger wire using needle-nose pliers according

9. Install the bracket to hold back the keyboard FFC cables using

support posts.

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connector at the back of the Wheelwriter and connect it to the host computer, then download

appropriate firmware into the Teensy. It will be necessary to cycle power on the Wheelwriter

after the download before the logic board will be properly operating with the firmware on the

USB Interface Board.

15. Reinstall the top half of the Wheelwriter case: pull the paper release and paper bale levers

forward; thread the LED panel through its hole in the case top; hook in the catches at the front

of the machine and then tilt down the back until the latches meet and catch; and finally snap the

LED panel back into place.

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To see details more clearly, try viewing the PDF file for this document online and zoom in. Better yet,

https://github.com/IBM-1620/Junior/raw/master/docs/wheelwriter-adaptation-CAD.pdf

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