On 2018/11/02 9:43 PM, Ivan Vegvary wrote:
Purchased used Variac. Good action, very smooth from 0 to 140V AC.
Question: Input and output are both 2 prong, no ground. Should I modify it to three prong with ground?
BTW, I do also own a functioning isolation transformer.
Should the IXformer be placed between the mains and the Variac? Please advise as to best procedure. Thanks. Main use of Variac will be to power up ancient tube equipment.
Thank you!


As long as the variac passes basic eletrical leakage test fine and the
powre cord and internal wiring are in good condition there is little
sense in trying to upgrade it to three conductor wiring.

In fact I recall reading somewhere (can't find the link) that it is
against the electrical safety regulations to convert two conductor
products to three conductor. This could be incorrect, until I can find
the reference take it with a grain of salt. However many items wired for
two conductor would need to be modified for three conductor beyond just
adding a ground - in pinball and jukeboxes the older two conductor items
correctly had the power switch on one side of the line and the line fuse
on the other - this is totally wrong on three wire setups!

So use the isolation Xformer to be safe.

Also, I trust you are aware of the series lamp (25 to 100W bulb
depending on the load) test for powering up gear that you aren't sure
hasn't a problem (shorted winding, cap, rectifier, etc.)...

John :-#)#
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