Reading MT/ST Tapes
phb.hfx at gmail.com
Sat Jul 31 12:40:24 CDT 2021
On 2021-07-31 1:19 p.m., Chuck Guzis via cctalk wrote:
> On 7/31/21 8:55 AM, Paul Berger via cctalk wrote:
>> Since there was still a few 360s around when I started I also got to see
>> the inside of a 1052 a few times, they are a really stripped down
>> keyboardless selectric. They used a function cam to space and since
>> they did not have a tab rack they would space a lot which would cause
>> the space cam to wear, I remember one that was so worn that when it
>> cycled it wobbled very noticeably, the customer would not let us replace
>> it as this was the console for the 360 and they did not want it
>> unavailable for the time it would take to replace it. Some customers
>> apparently would have a spare 1052 onsite. The keyboard on the 1052 is
>> the keyboard from a keypunch machine.
> Did the 1620 Mod II and the 1130 use the same Selectric mechanism as the
> S/260 1052? I remember that the Model B on the CADET always felt as if
> it would shake itself to pieces every time the carriage returned.
> And given the relatively high failure rate for motor drive belts, why
> did IBM persist in making replacement such a bugger of a job?
I have never seen either of these machines but looking at pictures of
them it looks like the first version of 1620 had a type bar typewriter
as a console. These type bar machine would have a common heritage with
the Flexowriters both are descendants of the Electromatic company that
IBM purchased in 1932 but later sold off what became Flexowriter due to
I did find a picture of a 1620 that does appear to have a selectric for
a console and it looks like it is a modified OP selectric even being in
the same case sunk into the desk so I suspect that it is the first
version of the selectric I/O.
The console on the 1130 does however look like it is a 1052 that has
been integrated into the machine.
Speaking of shaking apart on carriage return, I was once preparing some
cash registers for the local phone company in a room where the had a HP
mini that apparent ran some terminals for their subsidiary phone company
in Prince Edward Island. This HP had an ASR-33 for a console and it
seemed that it printed a line for every transaction and when it would
return it would slam into the dashpot on the left frame and the whole
ASR-33 would rock. This mini recorded transactions on punched tape that
was taken downstairs to the main computer room where it was read into
the IBM mainframe on a high speed punched tape reader that looked like a
3430 tape drive with the magnet head replaced by an optical head.
With regard to the position of the belt it is where it is because the
selectric mechanism is split into two parts. On the left is the cycle
shaft with the cams that position the type ball and through some gears
turns the print shaft that drives the ball into the paper. right in the
middle running inside the appropriately named center bearing, is the hub
that has the pulley on it that is driven by the motor this turn
constantly. on the left side of the the hub there is a torrington
clutch that when tripped turns the cycle shaft to print a character.
On the right side of the hub is the operational shaft that turns all the
time that have clutched cams on it to operate functions such as tab and
backspace, plus another torrington clutch for carriage return, and on
the extreme right a cam for shift that rotate the ball 180 degrees. It
would seem that the motor belt is positioned where it is so that the
entire machine could be operated from a single motor.
On OP selectrics changing the belt is not such a big deal, you take out
one of the gears that drives print shaft, remove the screws that hold
the bearing plate on the left end of the cycle shaft and the either back
off or remove entirely the cycle shaft. It was more of a challenge on
the original I/O because of the presence of contact block both at the
end of the cycle shaft and under the selection latches. The original
I/O was just a modified OP selectric That other than the addition of the
contacts and magnets the only other change was the beefier capacitive
start motor, I have seen this motor tear the teeth off a belt on a
jammed machine just by turning it on. You did not even have to look to
tell if a belt was missing teeth, they had a telltale thumping noise you
could hear as soon as you got close to it.
The I/O II was a lot better changing belts was pretty much the same as
an OP selectric and I don't recall having to change them as often. The
worst where the machines that where in a case like an OP selectric sunk
into a desk, that case and mount just made things more difficult.
Part of the fun of the banking terminals was some bank branches had the
machines on the counter, right where the banks customers are, and
customers would often feel obliged to offer some of their wit or wisdom
while you where up to you elbows in a greasy machine. I those days of
working on greasy mechanical machine we where obliged to wear suit and
tie, but greasy machines where not the worst, for that there was proof
machines with their purple indelible ink used to print endorsement
stamps on documents. After working on them you would have purple hands
for a few days.
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