[GreenKeys] Associated Press Teletype maintenance; UPI As Well

[Geo. Hutchison]

GO, CHARLES RING!!!!!!

The Extels that UPI used were dismal compared to the model 15.

A new Extel gave pretty fine looking print for maybe two months, and 
then the fan was sprinkled with substance.

The problem was with the print heads, and the cabling which coupled them 
into the electronics.

The needle guides in the first iteration of print heads were made of 
some very soft plastic material which wore quickly. The wear manifested 
itself in that the "focus" of the needles changed as the plastic wore, 
causing the vertical alignment to be come jagged and thus began to be 
hard to read.

Focusing was accomplished by changing the shims of the needle guide 
supports and thus realigning the vertical. It only lasted a few weeks 
and had to be looked at again.

A second generation print head needle guide had a much improved 
material, this taking longer to wear, and focusing was modified by 
making the needle guide supports adjustable so that the needles could be 
realigned three or four times before a new head was in order. Wear was 
also reduced by carefully filling the cavity behind the print head with 
a better lubricant. I used Conoco Super-Sta, a #2 lithium-based grease 
with a tackiness agent added that kept the grease pretty well where it 
should be.

HOWEVER - - -

Another fault with the Extel print head system was that the cabling was 
a flat cable with about a dozen conductors in it that ran to the circuit 
board through an oval slot in the deck of the typing unit, and plugged 
into the circuit board. The cable was held in place with a clamping 
arrangement with a bend in it such that the cable would not become 
sharply crimped as the print head ran back and forth.

Extel blew it by not using sufficient cable to allow the radius of the 
bend to remain a constant. As the head ran to the left the radius of the 
bend would change (decrease). This imparted a situation where the thin 
copper conductors of the cable would cold-work and thus harden, making 
the copper brittle and ultimately shattering into micro-thin copper 
strips that as they wore would cause the resistance of the cable to 
increase until there was essentially no connection through the bent 
area, starving the needle magnet(s) and losing the ability to print.

RCA hated it when we called for a replacement print head, as they were 
expensive. Some of us techs learned how to replace the cable, with a 
little extra length where it was needed, and would greatly extend the 
useful life.

The Associated Press did some cables which were a flat ribbon with the 
conductors composed of some mighty small gauge twisted copper. I have no 
idea how well that worked out, as about that time I won the Fur-Lined 
Pot and was sentenced to working on I/O Selectric Typewriters for Air 
West, Wizard Of Avis, and CIT Financial Services.

Extel also made a line of reperforators  that were extremely quiet, but 
had their own Achilles Heel.

The punch blocks were far more precise than the those made by Teletype, 
and therefor not really field serviceable.

You could renew the tape supply of a model 14 by sliding the oncoming 
new tape under the currently running out tape and they would keep 
chugging along. Do that with an Extel reperf and a new punch block had 
to be put in. They were REALLY REALLY Expensive, and RCA hated that, as 
well.

So there....

W7TTY