4 ms·
The power supplies I worked with on the Model 28 were the typical linear design. They had huge resistors on them that after a while, the heat from them would li
by chiph 8y ago
The power supplies I worked with on the Model 28 were the typical linear design. They had huge resistors on them that after a while, the heat from them would lift the copper pads off the circuit card. So they'd be hanging off the card, only held on by their solder connection. If the inspectors took a dislike to us, they'd write us up for them. But mostly they knew this was a design "feature" and would overlook it.
One of the cool things about that era of Teletype was the mechanical serial to parallel converter. This was a multi-lobe camshaft that as the pulses came in and the electromagnet selector engaged/released, would (if your timing was set right) select five bars (for your Baudot code) that controlled the position of the type box where all the letters and numbers were.
- Animats 8y agoYes, the usual Teletype loop current supply is a 120VDC supply with a 10K 2W resistor, to get 60mA constant current. Efficiency is below 10%, with over 90% of the power going to heating the resistor. That's partly why I built a switching supply interface. Far less heat. Small box, no ventilation required.
- chiph 8y agoI briefly considered taking one of the cards along to my high-reliability soldering class just to provoke a reaction from the instructor.. But figured it might bring down attention from On High into the state of our circuit cards and that wouldn't have been good. Besides, they lasted 5+ years like that before needing replacement. We pretty much only replaced them when the boards became brittle from the heat.