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Andreas Bombe
@activelow.net

Last weekend at #VCFe I once again encountered the meme that using original power supplies for your home computers of the 80s is bad because the line voltage was raised by 10% from 220 V to 240 V since then. #electronics #retrocomputing #vintagecomputing

Andreas Bombe
@activelow.net

So instead of 5 V, as the story goes, they now deliver 10% more and would be outside the specs. But no, that's not how voltage regulators in power supplies work. They regulate voltage. That's their one job.

Andreas Bombe
@activelow.net

There's of course a real reason not to continue using the CBM linear power supplies for their 8 bit computers: they didn't have protection circuits that would prevent a failing voltage regulator from potentially frying your computer.

Andreas Bombe
@activelow.net

In typical linear power supplies you have a (big and heavy) transformer and rectifier that generates a low voltage DC from line AC, followed by a linear voltage regulator that generates the desired target voltage from that.

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Andreas Bombe
@activelow.net

The regulator acts essentially as a resistor that takes just the value needed to drop the voltage to the desired level. That is, it converts the excess to heat. Higher input voltage means more excess and therefore more heat. But the output is a fixed voltage.