Electro-Neutronics Inc.

CD V-700 Model 6b

This is a Geiger counter originally used for Civil Defense purposes. This came in non functional. I checked all the semi conductors, diodes and transistors. I went through the resistors and found them mostly in tolerance. I tested the meter with an ohm meter and a 10k series resistor. I started with a 1 meg resistor and worked my way down dividing by half until the meter registered 1/2 scale. That satisfied me if the meter was good or not.

The unit came in with a spare used G-M tube. It only needed the loose pins super glued. Once the new G-M tube was in I measured about 600 volts on the tube. The scope showed the typical fly-back transformer weird wave shape by simply putting the probe tip near the fly-back transformer.

This was something new for me to work on. A hybrid mix of solid state and a G-M tube. It was fun. See the pictures below.

This schematic is inside the case.			Restored and operational. The probe holder and yellow stand-off is with the owner. He want to mold and duplicate a new one before the original breaks clean through.	Pre-restoration
Restored	Check CR6 Zener voltage of 15.5 at the collector of V4 fly-back oscillator.	Collector of V4	Glued plastic battery holder spacer.	The G-M tube ground depends on these two case contact points. They were pained and I did not like that. A file cleaned off the paint to establish a reliable ground.
Calibration on the right. I do not have a cal procedure nor do I have a radiation standard.

Hit Counter

Contact me including your thoughts and comments.

Please see the LINKS page. I have collected many resources over the years.

135,912 unique web site visitors (14,499,000 hits) from October 2004 through August 2011.

Copyright © 2004 - 2012. All rights reserved.