CHM visit report

[Bill E]

I spent all day today at the museum and had long talks with not only some of the people that restored it but also with Peter Samson about the music synthesizer and the -1 in general. I'll post a vid soon.

Top bits:

The lights on the pidp-1 are definitely brighter than the -1 there. OTOH, the lenses on those lights are from 60 yr old plastic, so what's authentic, now or original?

The reason for the 2 different color panels was, no reason. Some customers wanted white, some not. That was it.

The machine there is not the LLM one, nor the MIT one. It came from a company in Boston. The MIT one is in storage and not running, along with a non-working PDP-10.

The sound output did indeed have some analog filters, and they have the actual schematics and component values which they are sending me. My digital filter version is a very close match!

All of Angelo's efforts to precisely match timing was a bit of an excess, the clocks in the -1s were not particularly accurate so the cycle time was never exactly 5us. The subclocks were implemented with analog delay lines, so were also rather imprecise. Peter added 'tuning' to his music code to allow adjusting for each machine. He was fiddling switches to get the pitch right during the performance noted below.

I got to get up close and personal, getting access to the innards. Pretty amazing, enormous amounts of hand wiring. Assembly time must have been long.

The lower row of switches on the pidp do not match the real ones, the rest do. Closeup pic coming when I get home from SF. The real ones have a tapered handle as was reproduced in a prior post. I think I'll have to print some.

Otherwise, they look essentially identical.

Today was the once-a-year singalong. Peter played quite a few holiday songs and the crowd sang along, an old MIT tradition they resurrected. Interestingly, 3 of the -1 team there I talked with are MIT grads, and all my year. Small world.

The vid has Peter actually loading tapes and the music recorded, along with the blinking lights, of course.

Oh, once audience member showed up with his pidp-1!

Bill