IBM 029 Keypunch has arrived

Roger Holmes wrote: Ferro-resonant regulators are a type of AC regulator using a special transformer tailored to operate with the core around the flux saturation level. Operated in this manner the output is regulated because the amount the magnetic flux can change is limited. The transformer has a special winding on it with a capacitor (may look similar to a motor start cap) connected across, which is where the resonant aspect comes in, and hence dependance on the operating frequency. I don't know enough about them to say precisely what will happen when operated significantly off the target design frequency: whether the output will change, loss of regulation capability, excessive power consumption/heating, some combination of the above... other than to say I expect 50 Hz vs 60Hz is more than enough to matter. To my limited observation, IBM was rather fond of ferro-resonant regulators. I had an IBM modem/store-loop controller at one time, the logic power supply being a ferro-resonant transformer (no power transistors anywhere). It's one reason some IBM equipment seems excessively heavy, the ferro-resonant transformer (with cap) being typically heavier than would otherwise be required for the same amount of power.