[GreenKeys] Lorenz Lo15 - advice request!

[Mattis Lind]

Hello!

So I have been working with a Lorenz Lo15 teleprinter for some time.
Cleaned it. Removed old sticky dirty grease and added new fresh grease and
oil. Replaced three springs in the typing carriage and two brushes for the
governor. Adjusted the speed of the motor. It works quite well.

I designed a small circuit. Still in prototype. It is a step-up converter
that creates up to 120 V DC line voltage. Then I made a small hysteresis
switching current source that could generate up to 60 mA line current.

https://i.imgur.com/Jok5QL8.jpg?1

There is a small STM32 micro controller controlling desired output line
voltage and line current. It also can generate some simple test patterns.

The idea is to integrate RS-232, USB, and current-loop (yes for interfacing
an old PDP-11) to this circuit. It should be possible to attach it to a
Raspberry Pi to have more advanced services like i-Telex, news feed and a
standard Bash prompt from the Raspi. The prototype only consumes 300mA 5V
when driving the teleprinter so I think it would work well with a Raspberry
Pi driven by a decent USB charger.

But there are a few problems with the Lorenz Lo15 itself. Since it is very
similar to the Teletype model 15 I thought maybe the expertise here could
give some hints on the problems I have.

1. When printing past the rightmost end it stop spacing, it will not start
spacing again after a CR. It very often requires two CR to get it back to
spacing normally.

I found the spacing stop lever and put some oil there but it didn't really
help.

Here is how it looks when it is spacing normally:

https://i.imgur.com/XDzz9MM.jpg

And here is how it looks in the stop zone and also after the first CR:

https://i.imgur.com/kSPE1uy.jpg

Any advice regarding this?

2. I made a little program in the STM32 that send continous RY characters
and then a CR. After the CR the next character would be printed on the way
back. Is this normal and you need to insert a NUL after a CR or is my
machine to slow?

I know that I was fiddling with the return spring mechanism and it might
have lost a bit of the force. How can I adjust it to the correct CR pull
force?

3. If I send a BELL character it continuous to hammer the BELL whatever
characters I send until it receives a CR. It will BELL on the CR but then
for all the subsequent characters it will be silent (except for BELL
character..). Possibly this is some sticky grease somewhere I haven't been
able to clean out. But advice would be helpful!

/Mattis
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