Victoreen Model CD V-700 Schematic Diagram

Posted on Feb 5, 2014

This is the 6A schematic that was in the bottom of the unit. It is incorrect. These units have been banging around for over 40 years. Many bottoms have been switched around, due to battery corrosion in the lower case. My Geiger Counter is a 6B, and the schematic on the bottom is a 6A. When I was tracing the circuit, this drove me nuts, until I fig

Victoreen Model CD V-700 Schematic Diagram
Click here to download the full size of the above Circuit.

ured out what had happened. The annoying schematics do not give the Model #. This is a horrendous oversight in the documentation world. But then, the manufacturer never figured that the bottoms from 4 other types of radiation detectors would be switched around like crazy, over a 45 year period. The unit was DOA. Step 1 was to pull the PC board, and start checking things. Rather than take the time to make a tedious drawing, I simply took a photo, so it is easy to re-solder the wires back afterwards. I spent 10 years as an electronics technician, and 20 more as a semiconductor engineer. Many problems can be found simply by visual inspection, if you know what to look for, and this case was no exception. I measured the two diode junctions of the 2 transistors in the unit, and they looked fine. But close inspection revealed that the leads of the transistors were NOT SOLDERABLE when the unit was made. Four of the 6 transistor leads were tarnished beyond belief, WHEN INSTALLED, 44 years ago. The result was that over time, the lousy solder joints ceased being electrically connected. Not only can the tarnished leads be seen by inspection, but the solder did not form a proper fillet. The solder did not "wick-up" the leads, resulting in an extremely poor solder joint. Historically (1960`s), some transistor leads were NEVER properly plated with an easily solderable alloy, and many were plated with nickel, which hates to be soldered....

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