Antique De Forest Medical Device-Need info/parts

Antique De Forest Medical Device-Need info/parts

Post by BFredr89 » Mon, 12 Feb 1996 04:00:00



I ran across a 1924 De Forest Laboratories Medical Device rated at 250
watts.  Looks like it may have been used for electotherapy and surgery.
It has two rectifiers (4 pin small base with a small cap), 2.5-3 v
filiments and two triodes (4 pin large base with no cap) with 10 volt
filiments.  I have no schematic, but it is very similar to a transmitter
circuit with a plate voltage of 1100-1200 volts.  The unit has a 0-500 ma
meter for the grid circuit on the triodes and a 0-4000 ma meter on the
final output stage.  I have it all rewired and the transformers check out,
but I need tubes.  I am currently using 866's as the rectifiers, but the
original tubes had a small cap, where the 866's have a medium (possibly
816's would work).  The triodes may have been 211's, 845's or 803's, but
I'm guessing.  Any information on the parts or any doctors out there that
can provide some information on what the unit was used for would be
greatly appreciated.

                                                   Thanks,
                                                    Bruce

 
 
 

Antique De Forest Medical Device-Need info/parts

Post by Andrew Hofma » Tue, 13 Feb 1996 04:00:00


I can give you a little sketchy information. It is indeed a transmitter, and
was used for one of two things: either Cold Cautery or Diathermy. The former  
was also referred to as a "radio knife", and used high-powered waves to
simultaneously cut and cauterize unlike any other surgical device. It was
referred to as a "cold" process, since compared to a white-hot cauterizing
knife, it was indeed cold. It is based on a principle accidentaly discovered
by de Forest in 1907, when he zapped himself with the end of a fine wire
attached to the secondary coil of a radiotelephone transmitter. de Forest was
amazed that the deep cut in his finger didn't bleed and was in fact seared
shut.

Much later, he developed a Diathermy device (though he wasn't the first),
which affected the localized deep-heating of various parts of the body to
promote healing through "artificial fever". It used two applicator pads placed
above and below the body. His units were more compact than others, and were
widely acclaimed by doctors on a practical basis, but I'm not sure they were
ever truly accepted by the A.M.A. His first marketable version didn't appear
until 1934 or 1935. Given the 1924 date on your device, I'd say it's a radio
knife. Be careful.

More information of a largely non-technical nature can be obtained from
de Forest's autobiography, FATHER OF RADIO. A fascinating book, written by a
man who lived quite a life. On the flyleaf of the second-hand book I got (1950
edition), there is an inscription from the man himself: "To a good de Forest
Pioneer. With best wishes from - Doc. Lee de Forest." It's a 500-page
hardbound copy that originally sold for $5.00. Whatever story went with that
inscription is long since lost.

--
Andrew Hofman
LumaQuest Productions

513-643-7333

 
 
 

Antique De Forest Medical Device-Need info/parts

Post by Andrew Sieg » Wed, 14 Feb 1996 04:00:00


Quote:

>I ran across a 1924 De Forest Laboratories Medical Device rated at 250
>watts.  Looks like it may have been used for electotherapy and surgery.

Very likely used for radiothermy, i.e. using RF to generate heat within
the patient's body.  Generated tons of radio frequency interference, and
probably not very good for the patient either.  I don't know the current
state of the art for radiotherapy, but I expect that it's been discredited.
--