On Fri, 2009-05-29 at 10:44 -0400, Bill Degnan wrote: One thing that strikes me as odd is that they have a whacking great series resistor for running the fan on 240V, instead of using the mains transformer as an autotransformer... Gordon

Bill Degnan wrote: But it's missing the interesting part: the schematic for the amps isn't shown! Looks like a relay in the grey can amidst the tubes, I wonder if it's for chopper stabilisation or compute/hold/reset switching. (found pictures here: http://vintagecomputer.net/donner/) Interesting to see another variation on the educational analog computer. Sometimes I wonder if there weren't more educational models built than production models, although it may be one of those 'what has survived' issues. I have to finish up the writeup and photos of my Tyrotek sometime and put them up on the web. I would be interested if there are some example programs in there, to try on the Tyrotek.