Teletype 43

[COURYHOUSE at aol.com]

We need to  find a source of the pin feed  paper  for  the  43!  Also  a 
great thing  to round out the display  would be to have the  aux.  tape reader 
punch that was marketed   for it-  non working is  ok visually  - working 
would be  a  wonderful thing!
 
Ed#  _www.smecc.org_ (http://www.smecc.org)  
 
 
In a message dated 5/24/2017 8:26:28 A.M. US Mountain Standard Time,  
cctalk at classiccmp.org writes:

On Tue,  May 23, 2017 at 7:20 PM, Jim Brain via cctalk  
<cctalk at classiccmp.org
> wrote:

> On 5/23/2017 1:07 AM,  dave.g4ugm at gmail.com wrote:
>
>> You probably need a null modem  cable.
>>
> I had one (and used it), but not all null modem  cables are evidently the
> same :-)  I soldered up a loopback as  you suggested, and the unit dropped
> into DATA MODE on startup.  I  then played with the signals.  The unit
> really does want DCD to  be active, as just doing CTS/RTS, DTR/DSR, and
> RX/TX did not do the  trick.  Evidently, my null modem cable I had tested
> with  previously does not connect DCD. Swapped out for a null modem 
adapter
>  (from our old now deceased friend Radio Shack) and the unit works with  a
> new Dell M4800 laptop (so "newer" style +-10V RS232 levels must be  OK.
>

The minimum legit voltage swing for RS-232 is supposed to  be plus and minus
5 volts and the
maximum allowed voltage swing is plus  and minus 25 volts.  The problems
occur when gear didn't
bother to  do the negative swing to minus 5 volts.  Plus and Minus 10 volts
is  more than adequate.


The printer ribbon has less life left in it  than I anticipated, but a list
> member is helping me, so it should be  good to go after a deep cleaning 
and
> a light oiling.  I did  notice the printhead starts to stutter at times on
> long lines, but I  *think* it's a function of the damage to the ribbon, so
> we'll  troubleshoot that only if it continues after ribbon fixes.
>

The  ribbon on my 43 is a reinking type.  The ribbon loop is maybe  18
inches?  I have a new in bag
ribbon which I am sure is also  dried out.  I used a drop of thin oil on the
reinking roller the last  time
I messed with it and that seemed to work.  You probably want to  use
something that will lubricate
because the pins on the dot matrix  print heads do need that to keep them
from rusting and  wearing
out.

The "stutter" you mention is normal.  The printer  electronics buffers a few
characters during the slow
carriage return and  prints slightly faster than 30cps so when a new line is
started it goes at  full speed
until the buffer is empty at which point it goes into the  stutter mode.
This eliminated the need to send
nulls after a carriage  return that was necessary on the earlier purely
mechanical  printers.

-- 
Doug Ingraham
PDP-8 SN  1175