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Vintage threads from the first ten years

variable transformer enclosure

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4/14/2003 7:41 AM
Regan	variable transformer enclosure Stupid question probably, but is it ok to mount a variac in a metal box? I can't remember if the one i used to use was in a cast metal or some sort of bakelight casing. i have a metal box thats perfect, but just wondering for safety. Regan

4/14/2003 1:36 PM
Casey4s	Mine are in metal cases, just use reasonable precaution not to ground anything to your metal box/case. Casey4s

4/15/2003 6:16 AM
Regan	Re: variable transformer enclosure/thanks!(e) (e)

4/15/2003 7:23 AM

Re: variable transformer enclosure

It is OK to house them in a box. I would use a ventilated box if you plan to run much power through it. A nice case can give you room not only for a big satisfying knob, but also a couple meters to monitor output voltage and current. Maybe add an outlet. I had a bypass switch on my old box - so I could use the VAriac for troubleshooting, but once past its need, I could run right off the mains.

My current Variac has its own housing these days, and the enclosed one stayed at its old shop.

4/16/2003 5:37 AM

Thanks Enzo,
I like the bypass switch idea, and may add that.
I'm actually using an old computer power supply case, so it has ventilation and is pretty roomy. I'm using the original power cord jack, and the original power switch is moved to where the auxiliary jack(for monitor) was, even has the right spaced holes. A wall socket fits almost perfectly in the space where a flanged plate was holding the power supply and voltage selector previously. Where the fan was is where I'm mounting a meter, and I'm also mounting a couple of binding posts. I still have to drill the holes for the variable transformer and mount it. Everything is almost drop in- I only have to drill holes for the variac, and bust out some of the fan guard to fit the meter.
I'm still contemplating adding a small bypassable isolation transformer for using with small circuits so I don't have to have something else taking up space in the work area.
Which is more important, having a current meter, or voltage?
I don't have room for both, although I could make a small digital current meter using leds, and save the meter for voltage.
Regan

4/17/2003 7:58 AM

If you want to pick one meter to have, it would be current for me. Especially since I do mainly troubleshooting/repair.

When I have repaired a blown power amp or something and want to see if it is fixed, I will slowly turn up the Variac and watch the current. If it spikes right away, I don't care if it happened at 30 volt or 40 volts, I just know it happened way early and more work is needed. I always have a good idea what the voltage is from the knob anyway.

If you are doing some sort of design work where you are adjusting power supply levels or something, then the volts may mean more to you. FOr example if you have a functioning amp and want to vary the voltages a bit to check performance. Current may not be on your mind then. But mainly I watch current.

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