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View Full Version : Core memory voltages on a DCC-116



Nevets01
March 30th, 2020, 09:18 PM
So, I've been attempting to figure out the power supply off a DCC-116, a clone of the Nova 1200.
The regulated 15v rail, used to power the sense lines in the core memory, seems to be a bit high. I've been adjusting it using the trimmer pot, but I can't get it much less than 15.6 before it trips a crowbar circuit which clamps it down to 1v.
So, what are the tolerances on this sort of line? is 15.7 (lowest I trust to turn on every time) low enough, or will I get errors?
The manual doesn't give tolerances, only saying that it's "15 volts". I found a Data General manual which mentioned that the 15v supply was designed to range from 14.5 to 15.1 volts, depending on temperature of all things.

Thanks,
Nevets01

m_thompson
April 1st, 2020, 05:26 AM
Typically you adjust the core voltage to get a specific current through the cores. Sometimes the core stack will have a sticker on it that lists the optimal current, something like 300mA. On DEC equipment there is a loop of wire that the core current goes through. You clamp a current probe around the wire and adjust the voltage to get the desired current through the cores. The optimal current varies based on the core temperature, so there is usually a thermister in the core stack that adjusts the voltage and therefore the current.

Nevets01
April 4th, 2020, 09:16 PM
Got it figured out!
Nova is purring along happily! Now to try and archive the core before I accidentally wipe out its contents after 20-40 years of isolation...