Gregory's ServerThe right side of the teleprinter has four complex circuit boards: a CPU board with a Motorola 6800 (photo), a memory board, a communications board, and a printer driver board. Fortunately, these boards are somewhat documented: https://radionerds.com/index.php/AN~UGC-74 4/13
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 This board receives audio, amplifies it, and applies a 900 Hz high-pass filter. It also has some control logic. 6/13 The bits are encoded with two frequencies (Frequency-Shift Keying, FSK). This board uses a 64-bit shift register as a delay line to convert the 3600 Hz or 7200 Hz tones to bits. It also generates timing and control signals from the crystal. 7/13 The final board applies a 400 Hz low-pass filter to the output and sends the serial data stream to the communication board. It also has carrier detection, control logic, and regulated +5 and +12 volt power supplies. 8/13 There is a lot of control logic on these boards to power up the teleprinter when a message comes in and then power it off so it doesn't overheat. 9/13 The boards use standard ICs, but they mostly have weird military part numbers, making reverse engineering annoying. 10/13 The military teleprinter took all sorts of protocols: ASCII, Baudot, 45.5 to 1200 baud, but the Shuttle takes just one (unspecified) After reverse-engineering the boards, I think I know what type of signal it needs (ASCII, even parity, 1 stop bit, 600 baud, 3600/7200 Hz). 11/13 Hopefully we can get the teleprinter to print. But first we'll need to do some maintenance. A rubber roller turned to goo that was soaked up by the paper. (Sorry, no photo.) So we'll need to replace that. Stay tuned... 12/13 Thanks to Marcel for letting https://twitter.com/Curious_Marc, https://twitter.com/TubeTimeUS, and me work on this system. 13/13 @kenshirriff Incredible stuff! Please keep us posted on your progress! Did that type of print head/drum work by rotating to present a facet with the desired symbol in the desired place then transferring it to paper via a ribbon and hammer? If so, that is wild. NASA must've decided it was worth the weight budget to ship up this incredibly device. The frame looks like cast iron! I bet the symbol drum weighs a few kilograms by itself.    @kenshirriff Crazy. Makes me think if the rack for the printer was settled in the mid 70s and no one thought it was worth fighting for a newer, lighter printer as delays pushed the first launch to 1981. I can totally see the NASA and the Rockwell-Boeing-Lockheed Martin guys saying, "sure it's heavy, but we have these things printing away in B-52s for decades now. It's been field tested." *I'm spitballing that B-52s have these. But I do know that B-52s have text printers.   @kenshirriff Didn't those get replaced by a system that could also reproduce graphics? @spmatich Those chip are CMOS, but I don't know if they are military grade. I suspect that this board was a prototype so they may have used regular grade chips. @kenshirriff I wonder if this shares any code with my 1980ish 6800-based portable terminal and integrated spark printer 😄 |
The left side has three circuit boards, specific to the Space Shuttle. They interface to the Space Shuttle's systems so it can receive messages through the Shuttle's audio system. I reverse-engineered these boards. 5/13