Having now had a chance to take a closer look at the Creed to see why when Y is sent by the TDMS it prints as Z it is clear why! The following shows why… the TDMS is sending a continual stream of Y’s and then R’s:

This is the system between characters, all is well, but…

…this should be a Y, i.e. MSMSM (M = mark, S = space), but prints a Z, i.e. MSSSM.

And the R? This should be SMSMS, not SMSSS as shown. SMSSS is carriage return, no wonder then why the typehead remains firmly at the left of the platen.

But, checking the waveform output from the TDMS shows it is indeed sending a Y, and with a good square wave. This gets rather mangled when the teleprinter receive coil is connected but still has sufficient peaks to drive the thing. So the issue is between the input to the teleprinter and the selectors.

One item to note though is the three photos above are from a video recorded on my iPhone in ‘slo-mo’ – which proved to be really very useful here!

Time to read the manual more closely…

Work on the Creed 75 is slow at present and not helped by the fact the workshop is a mess since I moved all the valves in there and thus had to relocate all the other junk. Having recently reminded myself that 1/4 watt resistors do not generally like being expected to sink 3 to 4W (!) I have some decent resistors to ensure the PSU gives the required 20mA. So I have 80-0-80V from the PSU attached to the 444, I have 20mA (actually 23), the 75 types to itself locally, which is mechanical, but does not receive correctly.

I am generating code from the TDMS but Y comes out as Z and most other code combinations are unrelated to reality. I wondered if this was the result of the typehead not lifting correctly but Y and Z are on the same level. The ‘scope shows a reasonable waveform coming out of the TDMS.

So, currently I have two teleprinters and neither one reliably prints out what is sent to it. Nor do they talk any sense to each other. I can accept that with the 444 as I still need to strip it down but the 75 is all functional mechanically. The code combinations ‘sound’ reasonable too (if you’ve never heard a teleprinter you won’t know what I mean here) as with the motor off the clacking sound seems reasonable for the codes being sent by the TDMS. Very unscientific I know but it backs up what the ‘scope shows.

Some adjustment needed then… but really as I have yet to have any baseline in any of this it is a bit of a moving target. The TDMS will not send just one character but in theory, and with the motor off, given it sends the same character continually it should set the selectors correctly for me to examine them to see if Y as sent really is Y as received. That’s the next step, only the bench the teleprinters are on is too crowded to work on them.