Radio, railways, stuff...

...the slowly ongoing saga. Typical. I wired up the 50-way D connector and connected it all up and ... nothing. On checking voltages half was missing, i.e. -80 was there but no +80. The barretter was open circuit on one side. Huh. A new barretter arrived via eBay and so I now have the PSU fully working. A quick check of the 444 showed it to be no better than before, which I'd expected but I really wanted the correct power supply to verify that. So I connected up the TDMS to send data to the 444 and with the keys set to SMSMS it reliably prints Y - pity that should be R! Fiddling with switch combinations is equally confusing. So, progress, of sorts. However, the TDMS itself needs work yet because the circular trace is far from a circle, or indeed not even close to anything which might be imagined to be circular.

It's beginning to look serious now... I just need the time to solder up a 50-way D connector to connect the interface unit on the right to the 444. The interface has the +/- 80V supplies inside as well as all the interface logic for the various teleprinter functions. if I nick some volts out of it I should then be able to feed in the test signals into and out of the TDMS and use those to align the 444.

My latest toy arrived on Monday, a TDMS5BV telegraph distortion measuring set (TDMS). This guy (hopefully!) can generate a test pattern and all sorts of other magic to help test circuits (not particularly relevant) and also teleprinters (definitely relevant). It tests polar relays too, thus the socket on the front. I have a PDF of the manual and schematic for it. I now also have a variac so I carefully brought the TDMS up to voltage while watching the current and all seemed well - no exploding electrolytic. But it did nothing. After bothering to read the manual it gave instructions on how to prepare the instrument. After a fiddle with a control at the back it produced the required circular(-ish!) trace and the polar relay started to cycle. So far, so good...