JT9 blues

I thought I was going mad today. I wanted to print some rails for the FT817 and I already had the sliced files on the SD card in the 3D printer. I selected the first (there are two, one is a mirror of the other) and told it to print. Nothing. Reset the printer and tried again. Nothing. Opening the SD card on the Mac showed the file to be 0 bytes, which is certainly was not as I had printed it before. Ok, copy it again and try again. Nothing! Right. Delete all the files on the SD card - I have them all on the Mac anyway. Copy just the files for the rails across and try again. Nothing! Looking at the SD card via a terminal window - I must admit to be my favourite UI - it was full of all sorts of junk. Going duff perhaps? Ok, use a recycled 8Gb micro-SD in a holder, delete all the files currently on it, copy the rails across and try that. Ah, the files did not delete so it's full of old junk and I can't spot the files to print. Back to the Mac. Tried 3…

Recently our ageing HP 1022 printer has been misleading paper. There is a solenoid on the righthand side which controls the feed and the associated spring gets weak. I have stretched it three times so far, each time curing the issue for a while. A new spring is needed and, of course although I have a number of these they are all safely stored in the workshop never to be found! Coupled to the desire to print in colour and on reasonably thick paper - I'm thinking short ranges of 'special' QSL cards here - after a bit of research I chose a Xerox printer. Reasonable cost and - although as is typical with these things new toner costs more than the printer - aftermarket toner is affordable. The printer duly arrived and I set up the networking and it tried a test print. This failed to eject all the way and the printer announced it had a paper jam. Ok... try again. Nope. If I eased the sheet out as it was printing all was fine, but it never managed by itself. I did the usual things. Swearing at the printer failed to cure the issue as I had…

Having been unable to find any documentation at all for the CT100 TU I made a better effort at tracing the circuit out and I now think I know what connects to where. The magnet output is obvious, as is the audio input (TX output). I have now worked out the audio output (RX input) and traced enough of the circuit to figure out the keyboard input which has three connections for mark, space and tongue, the latter being connected to earth. The mark and space inputs pull down the inputs to matching nand gates and thence into the rest of the circuit. The keyboard connections were the last bit of information needed. Attaching headphones to the audio output I can trigger both tones by shorting each of the mark and space inputs. So far, so good. But... ...the keyboard outputs from the 75 are open circuit, yet at rest the 'stop' contact should be made and thus one of the keyboard connections should be connected to it. it isn't. A slight pressure on the contact makes it. Similarly, each of the 5 code contacts never 'makes' when operated (i.e. pressing a key and turning the motor by hand). But…