Victoreen V-715 Geiger Retrofit
The Victoreen 715 is a civil defense, cold war era, radiation instrument designed to
measure the high levels of radiation that would result from a nuclear
attack. Its ionization chamber is orders of magnitude less sensitive than
a Geiger-Muller tube and, in standard form, it is of little practical
use in the measurement
of low levels of radiation. It does have a quality die cast aluminum housing
and a classic look and feel so I have retrofited microprocessor based
modern digital electronics,
an LCD display, and a Russian SB-20 GM tube to the classic yellow case. The complete
unit is 2.41 times more sensitive than a Geiger equipped V-700 and perhaps 1000
times more sensitive than the original V-715.
Click here for assembly pictures of the first production unit
Picture above shows a V-715 retrofit operating as an on-line background counter
supplying the data to this site. The Netburner server, shown in the background
to the right, provides ethernet connection to the router and performs web hosting.
We can supply a preprogrammed Netburner for your site.
This (above) is a picture of the display in portable, radiation survey, battery powered mode.
C (upper right) is the accumulating count in the current 15 second interval.
The SBM-20 tube offers a sensitivity of 29 CPS at 1mr per hour and the calibration
of the instrument is based on this digital data. There are no potentiometers to
go out of adjustment. At the end of each 15 second interval the instrument displays
the calculated dose rate in mR per hour in the lower left section. In the upper left
the parameter Fm, for fast measurement, provides rapid integration of count
rate and emulates a meter. You get a rapid indication and measurement
of high radiation areas - no waiting for a count. This is best demonstrated by watching
the movie on the home page. The lower right corner alternates between battery percent
and GM tube voltage.
Pictures below show disassembled, non functional, units purchased surplus
for this retrofit .
Scroll down for more pictures showing the completed and running prototype of the
retrofit circuit board. Note the small surplus photoflash transformer left over
from the film camera days of yore. It makes things lighter and more compact
and, during testing, would produce a regulated 0-560V (with more available).
Output is set at 400V with the SBM-20 tube. Grey ribbon cable
connects to BDM pod used to download code. It is not present during normal
operation.
About the size of a pack of cigarettes ! Much smaller than the original V-715
innards ! Pictures below show assembly the prototype of this modernized V-715.
Rubber band is holding the battery carrier while the epoxy cures.
Picture below shows unit in the case, batteries installed, surveying radiation from
the Uranium Oxide coated 1940's era dish. With the aluminum case in place
the unit measures
Gamma radiation from daughter products. Alpha and Beta do not penetrate so the
reading is much lower - here it is .066 MR per hour. I have since cut a Beta
window and, with Beta, the reading is about 2.5mr per hour.
