The continuity test setting on digital multimeters could be used instead. It would show up a definite ground but the test voltage is too low to pick up what might be called ‘near’ grounds where, perhaps, the insulation has degraded. In our view, this test is best done with a standard insulation test meter.
All the above notes refer to the use of the growler to test dynamo armatures. We also use a growler as part of the testing procedure for all of our rewound magneto armatures.
The growler acts as a transformer as before but here we have two secondary windings – the primary and secondary windings of the magneto armature. The actual voltages induced in the magneto windings will vary with the number of turns/layers and gauge of wire used as well as the size and composition of the metal armature core itself. The design of the magnetic circuit and the number of coil turns in the growler itself will also have an effect so different growlers will give different figures for the same magneto armature. We always use the same growler for these tests so some factors are kept constant. As an example, previous tests have shown that, for a Lucas K2F armature tested on our growler, we should expect a primary voltage of 18-19v and a secondary voltage of 1200-1300 volts – which explains the use of the HV probe shown in the picture. Much variation on these figures would indicate a possible problem that needs investigating further.
CAUTION: DO NOT OPERATE THE GROWLER WITHOUT AN ARMATURE IN PLACE. Without an armature in the jaws, the current draw is greater and will cause overheating and possible damage to the growler’s coil.