On Tue, 22 Jan 2013 13:04:27 -0800, Steve Purcell
<steve.purcell.k@...> wrote:
Hi All,
I'm getting set up to work on tube equipment and I'm under the impression
that with old and unknown tube instruments it's best to bring up the
voltage slowly using a variac while monitoring the current for anything
unexpected.
Does that sound reasonable? As an integrated circuit guy I wouldn't have
thought that very useful but perhaps it is for tube circuits.
I have never worked on tube equipment where I thought it was
necessary. I usually use my variacs for power supply troubleshooting
where I already know something is not working correctly.
Another question I have is about what variac to purchase. There are some
cheap Chinese ones on e-bay but the real thing appears to be 10 times the
price. Since I'm just a hobbyist would the cheap Chinese one work well
enough or should I search for a used one of higher quality since I can't
afford a $900 Variac.
I pick them up used at garage sales, swap meets, and Craigslist and
build an enclosure if necessary. None of mine have meters as I have
found the dials to have fine accuracy. In one case I ground a
replacement brush from the carbon rod of a carbon-zinc D battery.
David Hess