RE: Variac

Subject:  RE: Variac
  Date:   Sun, 20 Apr 97 16:24:58 UT
  From:   "William Noble" <William_B_Noble-at-msn-dot-com>
    To:   "Tesla List" <tesla-at-pupman-dot-com>

Those prices for variacs are quite high - I see them at local swap meets
much less than half that (at the high priced vendors).  If I were you,
keep looking a bit - perhaps also you could  get someone on the list to 
volunteer to mail you one from one of their more reasonably priced
sources in 
exchange for some suitable consideration.  I saw but did not buy what I
as a 20?? amp variac in a dented case (it was about 12 inches in
diameter) for 
$85 last month.  There were some larger units there too, as well as some
rheostats from navy??surplus that would do - they were about $15 if I
right.  And there is always the cheapo way - get about 6 light bulbs -
say 60 
watt, 150 watt, 300 watt, 1000 watt, 1000 watt, 1000 watt (If you can
bigger than 1000 watt, then use that at high end) - put the bulbs in
with your xformer and provide shorting switches to bypass the bulbs one
at a 
time to raise power level.  There are some advantanges to this approach
the bulbs will protect the load by limiting power (as opposed to
voltage) and 
will also give you a visual indicaiton of true power level.   Edample 

   110 AC  
                      NO switches                               |
   110 AC
as you can see, to go from 0 power to full power, the sequence of switch 
closures is (numbering switches from top to bottom) 

Switches closed:        1 2 3 4 5 6 7
60w                     x 0 0 0 0 0 0
150                     0 x
300                     0 0 x
1000                    0 0 0 x
1500                    x x x x
2000                    0 0 0 x x
2500                    x x x x x
3000                    0 0 0 x x x
3500                    x x x x x x
full                    - - - - - - x

where X=on, 0=off, and -=don't care(recommend on)

by the way, be sure to read the table in a non-proportional font (like 
courrier) or it gets all shifted around.  Anyway, this is a really cheap
of making a high power rheostat with calibrated steps.  The switches can
toggle switches, or a high power rotary switch, or even relays
controlled from 
a nice rotary switch (or maybe even fiberoptically from a computer if
you want 
to be ultra sexy)


I`m on my way of finishing a nice 900 watt Tesla coil, I`ve finished the
cap, the RQ spark gap and cleaning up the neons, Im now looking for a
variac, there`s a store in Ohio wich sells surpluss electrical eq., I
asked if they had any good 10 amp variacs, they returned me a list of
variacs they had:

        For a new 18 amp 0-140v with knob and dial $185
        For a new 10 amp with dial and plate $130
        For a new 10 amp without dial and plate $105
        For a used 10 amp wihtout dial and plate $ 85

Are these prices fair, should I go for the 18 amp one, or does anyone
a cheaper mail-order place where to get this beasties, I know I can get
them for less at ham festivals but there are none here in MX.