Any Teletype ASR33 experts out there ? I have a couple
of problems with a teletype that recently came my way.
i) When I type a character from the keyboard in local
mode, something else gets printed. What gets printed
is not consistently the same character. I've watched
the selector mechanism while I hit rubout (all marking
codebars) and I can see that the codebars are not
being consistently selected betwee key presses:
sometimes I get 5 of them, sometimes 6 and
occasionally all 8. The high order bits seem to be
worst affected by this inconsistency. However if I
hold down the repeat key and select a character, the
right codebars are being selected. I punched a number
of characters onto tape to verify this and they seem
to be punching OK. This suggests to me that this isn't
an electrical problem since whatever code the keyboard
is sending is eventually being sensed correctly.
ii) In addition to i) above, even if I do get all the
codebars moving as required, the wrong characters are
being printed. I removed the carriage, cleaned and
oiled it and replaced it but this hasn't helped.
Any suggestions ? Are there any other diagnostic
procedures I can apply to figure out what's happening
here ? Right now the unit is not interfaced to
anything so any testing needs to be standalone.
Thanks,
Dave
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