AN/PRS-3 mine detector

The AN/PRS-3 mine detector was developed in the 1950's, and designed to compensate for soils with magnetic properties. This mine detector and the short-lived AN/PRS-4 were the last tube (valve) type mine detectors for the US Military.

 The basic concept is like the SCR-625, with the addition of the magnetic soil compensation circuitry. It uses eight miniature tubes, a 135 volt battery and a 1.5 volt battery. The user's technical manual is TM11-210, and the repair and adjustment technical manual is TM11-4074. It uses only two tube types, 1L4 and 1U5

I worked on one AN/PRS-3 mine detector, which worked, but two others I have tried have not worked.The level of complexity is far greater than a SCR-625 mine detector. As it is, it picks up a large metal object at 16 inches (40 cm), which is almost as good as the SCR-625s I have. However, it will pick up a screwdriver held on end, at 6 inches (15 cm), which is better than the SCR-625 will do. There is some background hum in the detector, and no volume control to reduce it.

A good source for tubes is http://www.vacuumtubes.net/

Note on the AN/PRS-4: After seeing a picture of a schematic of a AN/PRS-4 on ebay, it looks to be and updated version of the AN/PRS-1, that emits an RF signal, which could interfere with communications. Don't try to run one, unless you have a way of measuring the RF output, and know it is within legal limits.

In my military driver's license from the 1970's, I am listed as a AN/PRS-3 operator, though I never saw one.

Click on a picture to enlarge it.

135 volt battery under construction. Click to enlarge.

My license to drive a jeep, a AN/PRS-3 mine detector, AN/PRS-4 mine detector, a M113 Armored Personnel Carrier, and a Gamma Goat ambulance- back when typewriters were used.

Jan 2020 - A PRS-3 sells on ebay for $279, with free shipping. No pictures of the detector out of the case or bag; I expect it was some phony business going on.

Feb 2020 - Phony bidding on above detector! It is relisted.

Feb 2020 - The detector above sells for $54, with free shipping. No out of case pictures.

May 2020 - A PRS-3 with search coil damage, no bag, no case, no headset(?), sells for $75.

Jan 2021 - A PRS-3 in uncertain condition, sells for $50.

Apr 2022 - A PRS-3 sells for $120?

Old tube manuals online at:

http://www.bunkerofdoom.com/tubes/syl43/DATA/1949/1949.HTM