Each board has two separate summers (x1, x2, x5 and x10 gains); inverted and non-inverted outputs. Switching is same idea as for the integrators - in SBY (Stand by) mode the input jacks are grounded and disconnected from the op amp inverting input. The latter is connected to a potential divider (10k to ground (Ra in Jackson [1]) and 100 k to op amp output (Rb in Jackson)). The op amp can be nulled in this configuration. I've tried many different op amps; the TL081 (despite being obsolete) seems the best (and just 30 pence each!). The summers work fine up to 20 kHz - not too bad for the stripboard layout. And to quote Richard Hamming: The purpose of computing is insight, not numbers - by which I mean I am more interested in the insight the computer may give rather than how fast it might work.
Reference
[1] 'Analog Computation', A. S. Jackson, McGraw Hill Book Co. New York 1960, Figures 7-3 and 7-4.
Well, I think that completes the electronics for the second rack...next task is to drill the 212 holes for the front panel :(
Reference
[1] 'Analog Computation', A. S. Jackson, McGraw Hill Book Co. New York 1960, Figures 7-3 and 7-4.
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