"The Natural Philosopher" wrote in message
...
On 07/03/2020 10:31, charles wrote:
In article , alan_m
wrote:
On 06/03/2020 08:33, Brian Gaff (Sofa 2) wrote:
That sounds awfully crude to me, I'd have suspected something like a
drill speed control circuit. Brian


It probably depends on the age of the machine. The clue is in the
original post - the machine is 40 years old.

we did have transistors then.

1980? We did BUT mains level transistors were very expensive and even
triacs and SCRS were pretty dear.

The real power stuff - 400V MOSFET switches - didn't turn up till I was
out of that game in the late 80s.

And the intelligence to drive them reliably only got cheap in this
century.

That last is bull****.