Robinson photo cell amplifiers

Robinson photo cell amplifiers

Each tape drive has thirteen photo cells. Each photo cell needs an amplifier of three valves but the sprocket (which gives the timing information) needs four valves because it has to do a bit more work than the others. Therefore each tape-drive-amplifier comprises 40 valves and two amplifiers (for both tapes) giving a grand total of 80 valves! The photo shows one of the finished amplifiers (built from scratch by the volunteer team).






Wiring a complicated chassis like this demands a tidy approach. Here you see the initial wiring (right).













Then, later on, a few more components and wires were added.













But then we had a problem ...