Repairing Electrical Connectors Part of the Flexowriter pages by Douglas W. Jones THE UNIVERSITY OF IOWA Department of Computer Science

Contents

• Introduction
• The Current AMP Catalog
• Making New Pins
• The Repair

Introduction

The 75-pin plug and sockets

The 75-pin plug on our Model 2314 auxiliary paper-tape reader had several bent pins, and the most severely bent them broke off when we tried to straighten it. You can see this pin in the upper right corner of the plug in the left photo here. You can also see that the left jackscrew is missing from that plug.

This plug is intended to plug into one of the two sockets on the bottom of the Model 2201 Flexowriter. Looking at these sockets in the right photo, you can see that both sockets are missing their forward jackscrew (the top one in the photo) and one of the plugs is missing a polarizing pin.

These connectors were made by AMP (now part of TE Connectivity, Tyco Electronics), and both the Flexowriter and auxiliary paper-tape reader contain a number of similar connectors, with different numbers of pins, used to interconnect the wiring harnesses of the different subsystems that make up the machines.

In addition to part numbers, these connectors are stamped with quality-control date codes of the form YY-WW, where YY is the year (in the 20th century) and WW is the week. These date codes set a lower bound on the date of manufacture of our Flexowriter.

The Current AMP Catalog

We contacted TE Connectivity about the 201662-1 connector block. They say that this part was discontinued in 1995, along with its entire series, and they offer no additional information on it.

A search of the current connector catalogs from TE-connectivity shows that this connector resembles an AMP M Series Pin and Socket Connector. The pin spacing and geometry of the 75-position housing, M-series part number 201310-1 appears to be a close match for our connector. although the housing thickness (0.915") is considerably more than the thickness of housing for the flexowriter (0.770). The diameters of the holes that house the connector pins are the same (within the error of our measurements), but the position of the smaller-diameter retaining ring within the hole is different.

The dimensions of the AMP M-series pins, 0.062" diameter by 0.472" long, however is much larger than the dimensions of the pins in our connectors, 0.040" diameter by 0.200" long. It appears, therefore, that we will have to manufacture a replacement pin ourselves.

Repaired sockets

We found a kit for a jack screw that appeared to have the right double-lead tip insert in the TE connectivity catalog, part 201388-1. The tip and pin from this jack screw was, indeed, the exact part we needed to repair our tipless jack screw. Furthermore, the mating fixed jack screws we are missing exactly match TE connectivity's part 1-200874-2, and our missing male corner guide pin exactly matches part 1-201046-2.

The photo shows the repaired socket with the replaced jack screws and corner guide pin. The guide pin was easy to install, but to install the jack screws, we had to work through a thick layer of wiring. It is obvious that, during initial assembly, these screws were installed before the connector pins (with wires crimped in place) were inserted into the plug block. We used two-sided foam tape on the end of a coffee-stirrer to manipulate the nuts onto the backs of the jack screws, and then we used a jeweler's screwdriver to prod the nuts, tightening them. Finally, we used the hardened edge of the jeweler's screwdriver to dig into the relatively soft steel of the nut from an angle so that we could gently hammer the nut tight.

Making New Pins

Pin drawing and setup

I measured the dimensions of the remains of the broken pin, and the hole from which I extracted it. The original pin was made of a silver-plated brass stamping with a stamped stainless steel retainer spring wrapped around it. We cannot hope to duplicate that, but we can turn a replacement pin from brass rod and tin plate it. The drawing here shows the results of measuring the remains of the broken pin and planning to make a replacement. The photo shows the setup for making a new pin, with a blank chunk of brass clamped in a small lathe ready to turn.

The Repair

Replacing the broken pin

Before I got around to finishing the manufacture of a new pin, Willian Gathany found out about my interest in old Flexowriters and sent me three salvaged jumpers that ended with the appropriate pins. His father, Lysle Gathany, did field service for Friden. Cutting one of the jumpers in half, it was a simple job to solder the pigtail coming out of the crimped pin to the appropriate wire in the cable and then insert the pin in the connector shell. With that done, the cable could finally be plugged in.