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bombarding time


John,

Yeah, bombarding is pretty tedious. 

The one thing I found to speed up the heating time is to switch to a higher
kilovolt bombarder    -- kiloVOLT, not KVA.

Your typical bomber has from 12 to 25 kilovolts output, at varying
amperages.  (For a given KVA size, devide the KVA number by the kilovolt
output to figure your maximum mA output.)

The higher the volts, the higher the pressure can be in a tube and still
light up. The higher the pressure, the more air there is to heat -- makes a
big difference time-wise.

I use a $300 B&B-rebuilt powerline transformer with a Chokemaster choke.
It's 10kva with a 15,000-volt output. There are three lugs for the low
voltage on it (I believe all powerline-type transformers have these -- in
normal step-down service these form two 220-volt hot leads and the neutral
-- neutral is NOT to be confused with ground, in this case)

At any rate, in normal bombing mode the two "220-volt' lugs take 220 volts
in and turn it to 15,000 volts output, at around 800mA max.

However, if I take one "220-in" lead and the neutral lead, and apply 220
volts to these, the output is 30,000 volts, with a maximum of 400mA. 

It's basically overloading the coils -- what were intended in life for 110
volts are now receiving 220 -- but because the current is choked down it
doesn't hurt anything. 

Follow me so far? 

What I've rigged is a second contactor to switch the bombarder incoming
current to either "normal" or "high-voltage" use, with a little switch on my
bench and an indicator light up high to show me when in "high-voltage" mode. 

I start out bombing in "high-voltage" mode, 30 kilovolts. This means that
with two 8-foot straight tubes I can still leave 2-3 torr atmosphere in the
tube, and they heat up a lot quicker. With shorter tubes I can strike 'em as
high as 8-10 torr, though I usually go only as high as 4-5 torr, concern
being weirding-out the electrode with too high a pressure (Masonlite warns
of this, though I use primarily Neon Products electrodes.). 

Then, glass hot, I crank up the amps and cherry the 'trodes by flipping down
to "normal" mode -- 15,000 volts, up to 800mA.

If you've already got a powerline-type transformer it's worth it -- does
save a lot of time. I've used this rig for four years, no problems. Total
parts cost is only for the contactor, light and switch -- maybe $75 new,
less if used.

-Ted Pirsig
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