What moves the ribbon on a Teletype 43?
ard at p850ug1.demon.co.uk
Tue Feb 7 17:50:44 CST 2006
> I just got some new ribbons for my Teletype 43 and the print was
> (at first) nice and dark. But it soon started to fade. I watched
> the ribbon while printing and it didn't move!
> (There are two rollers on the left side of the typing unit which
> allow rotation only in one direction, and the ribbon is a
> continuous loop reinked as it passes through its cartridge,
> mounted at the right side). So obviously when *something* moves
> the ribbon, the ratchet action on the rollers prevents it from
> reversing direction, so there is net motion of the loop in one
> direction. It looks like the ribbon is intended to move during
> each carriage return.
> But what actually moves it? I don't see any source of friction
> other than where the ribbon passes over the printhead which is
> quite smooth. There is also very little tension on the ribbon
> (there is a spring mechanism that holds the rollers to the left).
IIRC, the rollers on the carriage have one-way ratchets or clutches too.
When the carriage moves one way (return?) the rollers on the carriage
lock, the ones on the frame slip, so the ribbon is pulled along by the
carrage. When the caraige moves the other way, the rollers on the
carriage slip, the ones on the chassis lock, and the ribbon is held fixed.
I asusme you have the printhead locked in the towards-platten postiion
(lever on the side of the carriage). If not, the ribbon will be loose.
> I don't have a service manual, just the basic operator's manual,
> and can't find one online.
I do have the KSR43 service manaul sometime. It's an odd book, it's got
diagrams with arrowns labelled '1 : disconnect cable' '2 : Release clips'
'3 : lift out power supply', things like that. Not like any other service
manual I've worked from. But it includes the schematics, and even
instructions on dismantling the print head, so it is quite useful.
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