A nice little addition to your setup, During my first job at a telco, I was in the TTY end of things, however at the time early 8 bit personal computers were the 'new thing', so my TTY fiddleings don't involve the earlier mechanical machines - we had Siemens M100's, that were on their way out to be replaced by Sagem TX20 machines. Line signalling for us was what we called 'double current', plus and minus 25mA from a plus and minus 50V supplies. For my shack I've dropped the voltage down to + & - 12V, the signals don't have to go that far, there is still enough to drive things, and I won't smoke the serial ports on my retro computer trinkets as I work to bring them 'online' TTY wise. With your new supply, I tend to think your letting the open circuit volts get a little high, add in a bit of back emf from the receiver magnets and maybe it's getting above a safe level that some gear can safely handle, too much contact sparks or too much for output transistors on your demodulators. Maybe you need something to take one loop as an input and generate several separate loops from it, so you can have a few machines receiving the same copy, but with the advantage of being able to handle one loop going open as you work on that machine without if affecting the others, as they are on their own loops.

Custom 19" panels really do finish a project off. I had one made for my repeater status panel but took me about 6 months to get to the wiring up stage..... Looks great, Eugene. Always look forward to your video's. Thanks for sharing, de M0SNR

Thanks for this! Excellent work. I am looking forward to part 2. Will you be able to show how you bypass the internal loop supply in the ST-6?