12 Jan
2011
12 Jan
'11
9:26 a.m.
I remember my first computer experiences were in
terminal rooms full of
teletypes. You realised just how noisy they were when the machine (a
DECSYSTEM-20) went down and all the terminals stopped at once. I would love
to get hold of an ASR33 but they seem pretty rare these days.
Don't forget THE SMELL of a room of working model 33's. I'm not sure
exactly what the smell was - probably a mix of ozone from the motors,
warm oil on the mechanical parts, and some of the smell of oiled
paper tape - but that was part of the experience too :-)
Oiled paper tape could actually go rancid under some conditions
(that I'm unclear about today!). I wonder if that's one of the smells
I remember. In particular the smell from the hoppers that
Caught the holes punched from the tape as being not the typical
Teletype smell but something stronger and more offensive. The hoppers
Were not necessarily emptied daily :-)
Tim.
12 Jan
12 Jan
1:11 p.m.
Don't forget THE SMELL of a room of working model
33's. I'm not sure
exactly what the smell was - probably a mix of ozone from the motors,
Why would an ASR33 motor emit ozone?
[All the AS33s I've seen have induction motors with no brushes or other
sparking contacts. Creeds often have seriosu-wound commutator motors (aka
'universal motors') with governers on them. They will spark.]
-tony
1:37 p.m.
On 1/12/11 4:11 PM, Tony Duell wrote:
Mine has an induction motor. There are contacts in the "hardware
UART", of course, but is there enough current flowing through that
circuit to result in anything more than the most insignificant of
arcing? If memory serves that's right in the 20mA loop.
-Dave
--
Dave McGuire
Port Charlotte, FL
Don't
forget THE SMELL of a room of working model 33's. I'm not sure
exactly what the smell was - probably a mix of ozone from the motors,
Why would an ASR33 motor emit ozone?
[All the AS33s I've seen have induction motors with no brushes or other
sparking contacts. Creeds often have seriosu-wound commutator motors (aka
'universal motors') with governers on them. They will spark.]
13 Jan
13 Jan
12:57 p.m.
Mine has an induction motor. There are contacts in
the "hardware
UART", of course, but is there enough current flowing through that
You mean the 'mechanical UAT' :-). There are no contacts in the receiver
section.
circuit to result in anything more than the most
insignificant of
arcing? If memory serves that's right in the 20mA loop.
It is. The transmitter loop consists of the distributor disk, nad hte
keyboard or reader contacts. No electronics.
Of course the 20mA loop could be driven by a fialry high voltage, and
could hkave an indcutive load (e.g. a telegraph relay), which could cause
some sparking But that seems unlikely in a computer applciation.
-tony
2:57 p.m.
On 1/13/11 3:57 PM, Tony Duell wrote:
Ah, yes. :-) I'm still fascinated by that setup after all these
years...My first exposures to serial<->parallel conversion were the
AY-5-1013 and the wonderful Z80 SIO.
Yes. But I suppose it's possible. Long wires might provide enough
inductance.
-Dave
--
Dave McGuire
Port Charlotte, FL
Mine has
an induction motor. There are contacts in the "hardware
UART", of course, but is there enough current flowing through that
You mean the 'mechanical UAT' :-). There are no contacts in the receiver
section. circuit to
result in anything more than the most insignificant of
arcing? If memory serves that's right in the 20mA loop.
It is. The transmitter loop consists of the distributor disk, nad hte
keyboard or reader contacts. No electronics.
Of course the 20mA loop could be driven by a fialry high voltage, and
could hkave an indcutive load (e.g. a telegraph relay), which could cause
some sparking But that seems unlikely in a computer applciation.
14 Jan
14 Jan
11:14 a.m.
On 1/13/11 3:57 PM, Tony Duell wrote:
Ah, yes. :-) I'm still fascinated by that setup after all these
years...My first exposures to serial<->parallel conversion were the
AY-5-1013 and the wonderful Z80 SIO.
My introduction to serial<->parallel conmversion was the ASR33 itself.
And the first thing I learnt was that transmission as a lot easier than
reception ;-). This is true however you do it (for example it's a lot
easier to bit-bang a serial data output than a serial data input).
The ASR33 transmitter looks slightly odd to British eyes. The Creeds have
one transmitter contact that is toggled one way or the otehr mechancially
for each bit -- that is there is a lever in the keyboard or reader that
actually represnets the bitstream in real time, it then operates the
switch. Some of the Creed readers have a sproket to move the tape that's
drtietly driven by the motore (the tape doesn't stop and start for each
character as it does in an ASR33) with the row of sense pins ('peckers'
in Creed's terminologu) in a slanting line across the tape. They are
lifted one at a time by a camshaft inside, sensing the holes in each
track one after the other.
-tony
Mine
has an induction motor. There are contacts in the "hardware
UART", of course, but is there enough current flowing through that
You mean the 'mechanical UAT' :-). There are no contacts in the receiver
section. 
12 Jan
12 Jan
3:29 p.m.
On 12 Jan 2011 at 21:11, Tony Duell wrote:
I did have, years ago, a Model 14 and I seem to recall that the motor
may have been centrifugal-start, rather than capacitor start. So
there would have been a small arc when starting, but that's it.
Mostly, the Teletype oil smelled funny.
--Chuck
Don't
forget THE SMELL of a room of working model 33's. I'm not sure
exactly what the smell was - probably a mix of ozone from the
motors,
Why would an ASR33 motor emit ozone? 
3:59 p.m.
Yup, I think it's the oil - and the current-loop circuit board. We've found most
of them to be at least browned, if not scorched, and in one machine it had become so hot
that one of the resistors had become unsoldered and fallen out! -- Ian
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-
bounces at classiccmp.org] On Behalf Of Chuck Guzis
Sent: Wednesday, January 12, 2011 3:29 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Teletype Tales Part 3
On 12 Jan 2011 at 21:11, Tony Duell wrote:
I did have, years ago, a Model 14 and I seem to recall that the motor
may have been centrifugal-start, rather than capacitor start. So
there would have been a small arc when starting, but that's it.
Mostly, the Teletype oil smelled funny.
--Chuck
> Don't forget THE SMELL of a room of
working model 33's. I'm not
sure
exactly
what the smell was - probably a mix of ozone from the
motors,
Why would an ASR33 motor emit ozone?
13 Jan
13 Jan
1:23 p.m.
Why would an
ASR33 motor emit ozone?
I did have, years ago, a Model 14 and I seem to recall that the motor
may have been centrifugal-start, rather than capacitor start. So
there would have been a small arc when starting, but that's it.
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