03-15-2015, 05:15 PM
Gary, one thing that may be a problem is replacing the copper oxide rectifier with a silicon diode.
As I seem to recall, copper oxide rectifiers have a very low turn on voltage, which means they begin conducting current in the forward direction at a very low voltage, By contrast, a silicon diode does not begin conducting significant current until the applied voltage reaches 600 millivolts (0.6 V). So depending on the circuit, there may be significant calibration errors at the low end of the meter scale using a 1N4007 silicon diode.
An old fashioned germanium diode like a 1N34, 1N295 etc, may be a better choice as these start conducting around 150-200 mV, which could minimize the error and give calibration closer to the original rectifier.
If you have access to the schematic and can post it, that would be helpful.
As I seem to recall, copper oxide rectifiers have a very low turn on voltage, which means they begin conducting current in the forward direction at a very low voltage, By contrast, a silicon diode does not begin conducting significant current until the applied voltage reaches 600 millivolts (0.6 V). So depending on the circuit, there may be significant calibration errors at the low end of the meter scale using a 1N4007 silicon diode.
An old fashioned germanium diode like a 1N34, 1N295 etc, may be a better choice as these start conducting around 150-200 mV, which could minimize the error and give calibration closer to the original rectifier.
If you have access to the schematic and can post it, that would be helpful.
