1920's Tesla Coil, Fischer Type H, 12 AMP !!

Hello !

I just received a 75 pound work of art! A 1920s Fischer Diathermy Machine, 
type H.  It is more of a cross between a Tesla Coil and a d'Arsonval Coil, 
approx. 12" x 12" x 18".

Usually d'Arsonval coils are high current Tesla Coil primaries, from which 
various taps are lead to outputs for varying voltages of high current and 
frequency for surgical work.  This particular machine has a large knob in 
the front that is attatched to a rack and pinion, which moves a primary coil 
over a secondary coil to adjust coupling (ie, intensity of current).  The 
secondary is almost identical to the primary, only one fits inside of the 

This machine had a large transformer, usu. 3000 volts.  It has 2 series mica 
condensers, and 5 MASSIVE finned stationary spark gaps with 1/2" tungsten 
discs.  This is the "heavy dutiest" of any spark gap I've seen in a 
diathermy machine, even more rugged than the typical Fischer gaps.  Very 
high current.

Now, the scary thought is that 12 amps of are being drawn from the mains.  
These 12 amps charged the condenser and were passed through the gaps in the 
usual fashion to the primary coil.  As the secondary coil is the same amount 
of turns, the current induced in the secondary is EXTREMELY high -- and THIS 
current was conducted DIRECTLY to the patient through metal electrodes.  If 
these electrodes were not in DIRECT contact with the skin, an arc would form 
instantly burning a hole in the skin!

Patients were often petrified, and Fischers large manual has a chapter 
devoted to preparing the patients for such scary treatments, and calming 
those already scared out of their wits!

Most of Fischers machines DID however have secondary coils made to give 
"high frequency effluve" or hot sparks, as well as the above "d'Arsonval" 
and "Thermo-Penetration" "Low/Medium/High" currents...however taps for these 
later currents were taken DIRECTLY from the primary, meaning a mis-fire of 
the spark gap leaves a patient firmly wired directly to a 3000V 6A 
Not exactly OSHA approved!

Jeff Behary

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