2. If 60 amperes cannot be obtained with the 0-25A LOAD,
decrease the field current control (41) to a safe level; then back off the LOAD
CURRENT CONTROL (43) to its minimum position (counterclockwise), while making
certain the DC voltmeter does not exceed 28 volts.
3. Turn the 25A LOAD switch (34) to the ON position; the DC
voltmeter reading should now decrease.
4. Bring the DC voltmeter reading back to 28 volts by
adjusting the field current control (41).
5. Increase the load current reading by adjusting the LOAD
CURRENT CONTROL (43) to 60 amperes. If not possible, repeat step (2); then turn
the 25A switch OFF and the 50A switch ON and continue with step (4).
(f) If test reading cannot be obtained, the generator is
unserviceable and must be repaired.
(g) This completes the test.
Turn the field current control (41)
fully counterclockwise (CCW).
Turn LOAD CURRENT CONTROL (43) CCW.
Remove all loads (34).
Decrease drive speed control (42) CW to OFF.
Depress stop button (35).
Remove all cables and leads.
(h) Remove generator from test stand and install the regulator
assembly for further testing.
(i) Return all controls to positions indicated in table 1.
(5) Indications from the test stand can locate the trouble area. For
example, if the rotor field is open, there will be no voltage or current indicated
on any of the meters, except when the internal battery is selected.
(a) An open rotor stops all alternator functions; so, when low
voltage and no current are observed, the most logical circuit to check would be the
rotor. It could be an open field coil or sliprings.
(b) If, during the test, field current is indicated on meter 2 of
foldout 6 and low load current on meter 1, or output voltage on the DC voltmeter,
the stator winding or the rectifiers would be the most logical points to check.
(c) When trouble occurs one should first expect an operator fault,
such as a switch in the wrong position. In testing without a regulator, if the
field current switch (36) is in the REGULATOR position, you will have all the
symptoms of an open rotor field winding.
1. If the battery voltage selector (31) is in the wrong
position, bad indications will result. So doublecheck this switch.
2. Another switch that may give you trouble is the 0-25A load
switch (34). Procedures will require the adjustment of the LOAD CURRENT CONTROL
(43) to increase the load current. If the 0-25A load switch is OFF, the LOAD
CURRENT CONTROL will not vary the current in the load.
OS 010, 4-P14