Trouble with ASR33

From: Eric Chomko <vze2wsvr_at_verizon.net>
Date: Sun Mar 16 14:28:00 2003

This has me thinking that I should drag mine out and test it. Being the
new millennium and all...

Tony Duell wrote:
>
> > I'm currently fighting with an ASR33 trying to make it perform a carriage
> > return. Currently, the carriage is stuck all the way on the right side
> > and refuses to budge. I tried to find something inside that would release
> > it but I haven't located the magic tab.
> >
> > I've noticed something else. When I have the punch turned on, the '8' bit
> > doesn't punch. For instance, if I hit "RETURN" I get the 1 + 4 + 128 bits
> > punched, but no 8 (1 + 4 + 8 = 13).
>
> The 2 problems could be related. The 'block level description' of the
> machine is :
>
> Incoming data goes to the solenoid on the RX mechanism (rear left of the
> 'typing unit' (main chassis)).
>
> The RX mechanism samples the position of the solenoid armature (there's a
> camshaft in the middle of said unit), and thus converts the data to parallel.
>
> The parallel data goes onto the rails that run across the machine under
> the carriage (one rail for each bit).
>
> 3 mechanisms use these rails :
> a) The carriage, which decodes printing characters and prints them
> b) The punch, mechanically coupled to the left end of the rails
> c) The function unit ('Stunt box') which decodes control characters and
> performs the appropriate function.
>
> So if the return character is not getting to the rails correctly then
> firstly it won't punch properly and secondly, it won't be detected by the
> approipriate lever in the function unit.
>
> So let's get that missing bit back first. Are you running the machine in
> LOCAL mode (i.e. from its own keyboard to the printer?). If so, the
> problem could be in the transmitter side (contacts on the keyboard, for
> example). Or it could be a problem in the RX unit (sticking lever). I
> think it's safe to assume that the solenoid driver is not the problem
> here (it's not going to mangle only one bit).
>
> Incidentally, the carriage is fed by the 'spacing mechanism' which drives
> the left hand sprocket for the toothed belt. At the bottom of this
> sprocket shaft, right against the casing, is the spacing ratchet with the
> pawls to move it on one character, and to allow it to be released for a
> carriage return. IIRC, _carefully_ frobbing levers in this area will
> release the pawls and allow the carriage to return.
>
> > Whoever designed the ASR33 must have sold their soul to the devil to make
> > it all work. It's amazing how intricate and delicate everything is, and
> > how damn kludgy as well.
>
> I find them rather beautiful...
>
> -tony
Received on Sun Mar 16 2003 - 14:28:00 GMT

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