Radio and rails...

...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...

I seem to be collecting projects but making no progress on any of them! Well, ok I have five on the go, of which one is started and one nearly, and three are in boxes still. Since Es’Hail-2 (QO-100) went up I've been planning to set up a receiver for it, and later on hopefully a transmitter as well. One thing at a time (or in my case it seems no things at any time!) So, I have an acceptable LNB, not a good one but should suffice until I get a more decent one. I now have a bias tee, some relevant connectors, I have a roll of CT125 satellite cable somewhere and I am now waiting for a 120cm satellite dish and pole to arrive. If this arrives today I may even get it working by tomorrow, otherwise next week. The Creed 444 is the one project that has at least had some progress. For that, I now just need to wire up the 50-way D connector to the signalling unit and then it should type to itself, otherwise it will need adjusting as that's all that is left if the text is still garbled. Then there is…

Well I fiddled with the teleprinter some more, wondering if I could at least get it to print with just 30-0-30VDC - it needs 80-0-80. Nothing. I tried connecting directly to the relevant pins for the receiving relay but could not feel any resistance when this was applied. Odd, because I could measure its resistance with a multimeter, so what's up. Strangely the next time I tried I could no longer measure the resistance. Might have been me. Then it occurred to me that on the 444 everything comes out on the 50-way D connector and you can get directly at the receiver coil, and I can see the relevant ohms. So, re-wiring the lash-up and still with 30-0-30V and with a resistor in series just in case and it burst into life. Almost. It did print, or rather tried. It got most of the letters wrong, but is at least trying. Most likely the voltage is just not quite enough, or my lash-up resistor is denying it sufficient current but I'd rather not risk the coil right now. However, and more of a concern was that although it went through the motions, the carriage did not move. It was…