Fill-in project finally started

A project log for SBC-85 Remex Tape Reader Interface

Creating an I/O interface between the SBC-85 and generic Remex Paper Tape Reader

craigCraig 03/17/2020 at 19:240 Comments

The PCBs for the Remex Tape Interface were in last month's batch and it is now its turn to be built before the next batch arrives.  This was always intended to be a fill-in project for when I run out of other things to do, so we will see how far I get before something else comes up.  This is one of the simplest PCBs i have done, but it was completed in a rush to get the job submitted with an existing order at the PCB house, so there are bound to be mistakes.  I have fallen into the "cheap PCB" trap where for 50¢ per board I just don't put as much care into double and triple checking like in the old days. Who else remembers the amount of design review necessary when we paid dearly for each square inch of PCB, plated through holes were extra, paid extra for each via, paid extra for soldermask, extra for silkscreen (each side), and still waited 6-8 weeks for boards?  And that delivery calendar didn't start until the tubes of rolled up vellum arrived and were accepted at the PCB house.  Now I complete and see the design on the computer, upload files in 3 seconds, receive confirmation of build later that day and by morning the real-time update shows the pcb is 40% completed.  I can hear you saying "OK boomer" but, nonetheless, it was the stone age of PCBs and somebody needs to tell the next generation how deep the snow was on our up-hill walk to and from school.

So here is the board, simple parallel interface on the left to the SBC-85 I/O port, 74541 buffer, then some RC filtering on the signals from the tape reader and a DB25 to the tape reader on the right side.  Rows of LEDs along the bottom to see command signals being given to the reader and what the track is sending back.  The board is pretty generic, so it should be useful as an interface to any parallel port and to nearly any Remex tape reader.  Not all of the Remex readers respond to all of the signals, but I have found that they are consistent in the pinout so i think this board will work with the 4 or so different models of readers I have and probably for any Remex and possibly other brands.