Trouble with ASR33

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Mon Mar 17 18:36:57 2003

> On Sun, 16 Mar 2003, Tony Duell wrote:
>
> > 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.
>
> I haven't be able to verify what character is being produced because the
> durn carriage is stuck on the right. Once I get the carriage returned
> then I can determine what's going on.

Sure you can. In fact the carriage won't help you much anyway because it
onlly really decodes printing characters.

Look at the selector rails. You'll see there are 8 of them (at least
where they connect to the punch), and it's not hard, even without the
manual, to work out which state is a 0 and which is a 1, and what the bit
sequence is. Then you can see how they're set for each character.

Another trick is to use the reader. Open the cover (trivial for you),
hold down the tape sensor, and turn it on. Then hold down various
combinations of the pecker pins and see what happens. If you can get a
friend to help,, you could probably hold down the right combination for a
CR -- and see if the carriage then returns. If it does, then you've got a
keyboard problem, of course.


>
> > 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
>
> Yes, LOCAL mode.
>
> > 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).
>
> While I can't say I examined it to the point of ruling this out, I didn't
> notice anything wrong with the levers. However, it is an obvious place to
> start.

Actually, since you're working in local mode, I'd start with the keyboard
and distributor contacts. The former, particularly, are known to give
problems in old machines.

-tony
Received on Mon Mar 17 2003 - 18:36:57 GMT