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Hot Rodding a CDV700 Geiger Counter

Hot Rodding a CDV700 Geiger Counter

This project involves making several modification to an early 1960s era Victoreen CDV700 or CDV600-6B geiger counter.
Circuit modifications include:

Conversion to a single 5-cell NiMH rechargeable battery pack.
Adding a voltage regulator to the geiger counter’s main supply.
Adding a secondary voltage regulator to the 3V supply.
Adding a front panel LED power indicator.
Adding an external power input jack for charging the battery.
Adding a small solar panel for charging the battery.
Reducing the radio emissions from the geiger counter’s oscillator circuit.


The original power supply for the CDV700 and CDV700-6B uses two pairs of D cell batteries. The 3V-6V battery set supplies the oscillator circuit with 33ma of current when properly adjusted. The 0V-3V battery set supplies the detector circuit with a few ma of current. This causes the batteries to wear out at different rates.

Conversion to modern NiMH C cells allows the counter to run for longer periods of time. The rechargeable batteries work well with a small solar panel for recharging. A set of 5 AA-size NiMH cells would also work for this application. NiCd cells can also be used, but NiMH cells have higher power density and are less toxic.

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