[AMRadio] Old X-Ray Gear High Voltage Available

D. Chester k4kyv at charter.net
Sun Dec 24 12:44:36 EST 2006

----- Original Message ----- 
  When the building went up for sale there was a Hazmat asessment done
that did not indicate a PCB problem...   The tubes are of collectors 
interest only and would not be left in
the machines if removed.
  I was hoping someone like yourself might know of a collector or Museum
that would be interested.
The table and source mechanicals are a work of art and could be used
for milling or other light duty fabrication where a stable and
ballanced floating tool was needed.
   I thought if maybe the smaller HV transformer had a 220 pri then it
would be of a usable voltage at 110.
Will know more specs in a day  or so since I am now at the site.

In the early 60's I found an old fluoroscope (looked like 30's or early 40's 
vintage) in a rubbish pile, dumped outside of a building that was being 
remodelled.  I hauled it home.  The transformer unit was rated at 100 kv at 
something like 50 ma.  The transformer was a  rectangular core type, and the 
tube was enclosed in the middle of the core, between sections of winding.  I 
suspect this construction was used to allow the transformer core and 
windings to double as shielding.

The unit was dry; all the oil (PCB, no doubt) had leaked out.  I hauled the 
thing home, first with the idea of parting it out, but I had a can of 
transformer oil (probably containing PCB) from an old pole pig I had removed 
from the case, so I filled the x-ray machine with oil and fired it up.  It 
worked to the point that I could get the screen to glow brightly through a 
1/8" steel rack panel.  I played with it a few times, using a mirror to view 
the image to avoid exposure to x-rays that made it through the screen.  But 
I quickly decided it wasn't a good idea to fire the thing up after I noticed 
that a geiger counter sitting on the other side of the room, with the 
machine in operation, emitted a sound just like power line noise on a radio 
receiver.  Those old machines were notorious for emitting stray x-rays in 
all directions, not just from the little window located behind the screen.

Since those old fluoroscopes used x-ray energy to directly illuminate a 
fluorescent screen, I could imagine the dose of radiation the doctor must 
have received every time he used the thing, as well as the nurse, office 
personnel and patients in the waiting room near where the machine was in 
operation.  Of course, this was in the days when many shoe shops had 
fluoroscopes to x-ray a customer's feet to see how well the shoe fit.  I 
have heard tales of kids playing on the machine while their parents 
purchased shoes, taking turns x-raying their feet just for the novelty of 

I dismantled the machine, and gave the transformer/tube unit to another ham 
who claimed he had a use for it.  The part that I kept, and that I wish I 
had never got rid of, was the autotransformer.  It was a tapped 110v 
autotransformer,  rated at about 15 amps, with over a half dozen taps, 
selected with a heavy switch, to feed the x-ray transformer at varying 
output voltage from about 50 kv up to the full 100 kv.  The x-ray machine 
had two controls: kilovolts and milliamps.  The higher the kilovolts, the 
"harder" and thus more penetrating the x-rays.  The milliamp control was a 
filament rheostat for the x-ray tube.  The higher the milliamps,  the 
brighter the image on the screen.

That tapped autotransformer had output of about 60 to 120 volts in steps of 
a few volts each.  It made an excellent variable voltage a.c. supply for the 
plate transformer in my transmitter, with extremely good regulation.  I 
later replaced it with a 20-amp variac, which was a mistake, because I have 
never seen a variac with anything near as good output voltage regulation as 
that tapped autotransformer.

The machine was a thing of beauty, with milled art-deco design, and black 
wrinkle finish, on both the metal case of both the autotransformer unit and 
the part with the hv transformer and tube.  There were a couple of high 
quality meters, an a.c. voltmeter and milliammeter as well.

That ancient machine had some useful components for a QRO transmitter, and a 
quaint 1930's look, but I wouldn't recommend firing one up, since any amount 
of radiation has the potential for biological harm.  Modern day x-ray 
machines emit a tiny fraction of a percentage of the dose of those old 
fluoroscopes, yet they still take precautions with lead aprons and other 
shielding to proctect both patient and medical personnel using the machines. 
Fluoroscopes for fitting shoes have long been outlawed.  Those things were 
especially dangerous, since the x-ray beam was aimed up through the feet, 
directly toward the genitals.

I fired up  that machine over 45 years ago when I was about 19, and have 
never experienced any known ill effects from it.  I didn't turn it on but a 
few times, but I sometimes wonder if the x-rays might have had something to 
do with my developing cataracts later in life.  They were discovered during 
an eye exam when I was about 35, but I didn't notice them in my vision until 
I turned about 40.  They eventually impaired my vision and I had them 
removed about 3 years ago when I was past age 60.  Supposedly, cataracts can 
result from radiation exposure, and have been known to affect jet pilots and 
flight attendants, since a person is said to experience about the equivalent 
of one modern-day medical x-ray on a coast-to-coast or transoceanic flight 
at 35,000-ft. altitude due to natural cosmic radiation .

I would say that  the x-ray machine might make an interesting museum piece, 
or the hv transformer might have some other uses.  It would make a dandy 
spark transmitter or driver unit for a Tesla coil.  Much better than a 
typical neon-sign transformer normally used for those projects.  If there is 
an autotransformer, it would make a good substitute for a variac.  But I 
would not recommend firing up the x-ray tube.

Don k4kyv


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