Eimac "Medical Pulls"

[LeapFrog]

Hello gentlemen, I hope this is an acceptable question to post in this sub-forum.

I often here of certain tubes for sale described as a "medical pull", such as
with this eBay Auction.

This particular tube in question was a medical pull where it was no doubt used in high current pulse application and the tube was marked defective.This tube may still work as a spare in a transmitter and put out reasonable power but it is obvious from the testing that it is on borrowed time.

What medical equipment specifically, required the 3CX1500A7/8877 tube(s) to operate, and was the device generating RF in its original application (3CX1500A7) ?

Perhaps an early M.R.I. machine?

Thank You,
&
Best Regards.
-"LeapFrog" a.k.a. Sam

 

[Captain Kilowatt]

Yup.....older MRI machines and diathermy machines. Since RF is an electromagnetic wave the magnetic component of that wave can be used for all sorts of stuff that requires a magnetic field such as MRI units and induction heating/welding.

 

[Road Squawker]

Yup.....older MRI machines and diathermy machines....

one of the better uses of 27 MHz.

 

[LeapFrog]

one of the better uses of 27 MHz.

Starting to hear what you are saying, some straight-up-vile talk on 11 meters!
Thank You Captain Kilowatt!

 

[Road Squawker]

Starting to hear what you are saying, some straight-up-vile talk on 11 meters!
Thank You Captain Kilowatt!

LOL, My point really was about Diathermy machines (on 27.33 MHz) being the primary user of 11 meters.

 

[LeapFrog]

LOL, My point really was about Diathermy machines (on 27.33 MHz) being the primary user of 11 meters.

Yes, I read 27.20 mHz (or close to it) in the wiki article; kind of interesting how close to the 11 meter band these machines operated at, granted they pre-date the "11 meter band" I could see why the term "medical pull" exists now, thanks guys.

 

[BBB]

Some of the above mentioned medical equipment were on service contracts. So every six months (or some other pre-approved time span) a service tech would do on site preventative maintenance to the machines.

Occasionally that would include replacing the tube, even if it wasn't bad, so the machine would have better mean time between failures (MTBF) A savvy tech would hold on to these, instead of filing them in the round file, and pass them on to their ham buddies or sell them out right at far below distributor prices for new tubes.

A lot of machines used the venerable 8877 tube and its variants so start your "medical pull" tube collection today!

 

[nomadradio]

The official ISM (Industrial, Scientific and Medical) frequency is 27.120 MHz. There is another one at exactly half that frequency, 13.56 MHz. Popular for machines that melt vinyl plastic to feed into injection-molding or vinyl-plastic "welding" machines. The "Industrial" side of this frequency allocation.

Also used for plasma generators that do vacuum-deposition of metal coatings or high-power gas lasers. The "scientific" side.

The old tube-type medical diathermy machines all ran at 27.120, but the frequency was not stable. The carrier from those would sweep across five or ten channels as the power was pulsed on and off. The "whoop, whoop" or "grunt, grunt" sounds you would hear back in the 70s and 80s were coming from those.

Modern versions of those tend to have crystal control and stay on one frequency when they're operating.

73