Current
limited variac
useful in repairing vintage equipment
by sv3ora
This is a simple 1000VA current limited
variable AC PSU I made to slowly "bringing into life" the vintage
equipment I service. But it can also be used as a source for a variable
PSU (AC or DC).
It is just a variac and a series 100W 230V incandescent bulb. I
built everything onto a wooden board with 4 rubber legs below it. The
variac, the bulb socket and the output plug, are all firmly screwed
onto the wooden board and care has been taken so that there are no
exposed wires. For this reason, a switch or a fuse was not used, but I
powered this up from an external commercial fused switch.
Note that I built the first schematic on the picture above. An even
better version, would be the second schematic, which includes an
isolation transformer before the variac and a bypass switch for the
bulb. However, a 1000VA isolation transformer costs around 120 Euros
and I did not want to spend so much on it currently. All of my vintage
gear currently, have transformers, switches and fuses inside, so isolation is provided by
those transformers anyway.
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