PDP 11 gear finally moved

Eric Smith spacewar at gmail.com
Thu Jul 23 16:27:04 CDT 2015

I wrote:
>> I proposed it, and was willing to build microcontroller-based boards
>> and write firmware, but IIRC it was decided that there was too little
>> benefit.

On Thu, Jul 23, 2015 at 12:00 PM, William Donzelli <wdonzelli at gmail.com> wrote:
> That seems odd, considering the lengths you guys took on the caps, and
> the whole museum mentality of keeping things "safe" for the artifacts.

There's no artifact safety issue for the PDP-1 power supplies.  They
use a ferroresonant transformer, rectifiers, and filter capacitors.
If any of those fail, the machine won't work properly, but it won't be

If there had been voltage regulators, the failure of which could have
resulted in serious overvoltage, we probably would have added crowbar

In the Type 30 display, it's possible, though rather unlikely, for a
failure in the deflection power supply to blow the deflection drive
transistors. Adding a microcontroller isn't likely to avoid that. A
crowbar circuit might be useful, though the damage happens so quickly
that the deflection transistors might still fail.

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