Diode:

ELECTRICAL

from any stator lead to the frame, the windings

are grounded. If the lamp fails to light, or if meter

reading is high when successively connected

between each pair of stator leads, the windings

are open. (Fig. 13)

Figure 13.

range scale on the ohmmeter should be used, and

the ohmmeter should have a 1-1/2 volt cell. To

Figure 12.

determine the cell voltage, turn the selector to the

lowest scale, and then connect the ohmmeter

b. A short circuit in the stator windings is difficult

leads to a voltmeter. The voltmeter will indicate

to locate without laboratory test equipment due to

the cell voltage.

the low resistance of the windings. However, if all

other electrical checks are normal and the

b. With the stator disconnected, check a diode in

generator fails to supply rated output, shorted

the heat sink by connecting one of the ohmmeter

stator windings are indicated.

leads to the heat sink, and the other ohmmeter

lead to the diode lead, and note the reading. (Fig.

14) Then reverse the ohmmeter lead connections,

and note the reading. If both readings are very

NOTE: Each diode may be checked

low, or if both readings are very high, the diode is

electrically for a shorted or open

defective. A good diode will give one low reading

condition.

and one high reading. Check the other two diodes

in the heat sink in the same manner.

a. One method of checking diodes is to use an

ordinary ohmmeter commonly found in service

To check a diode mounted in the end

stations. The lowest

B-62