olivetti programma 101 repair

[Rick Bensene]

Simon C. wrote:

> I've taken the electronics module apart as I want to find out where the clock
> is generated or derived from as there is no xtal on the machine and there is
> no ac from the psu going to the electronics.
> 
The clock is likely derived from a simple R/C oscillator, with some buffer drivers on the output(s) to provide enough drive current to feed the clocked logic of the machine.  No crystal is really needed.

Variations in clock speed over time isn't really a big deal with electronic calculators.  The key thing is that the designs based on delay lines usually have some kind of timing bit(s) that are injected into the delay line that help sync the timing of the delay line with the rest of the clocked logic.

Most old electronic calculators had main clock speeds (which was generally always divided down to various phases) in the 40KhZ to 100KHz range.   Even at these modest speeds, it was easy for the machines to be much faster than the mechanical machines that they very quickly made obsolete.

-Rick Bensene