MAINTENANCE OF THE GENERATOR SET
Section I. CONTROL BOX ASSEMBLY
This section covers direct support and general
support maintenance of the control box and com-
It includes the frequency converter,
output selector switch, relay panel, field flash
switch, current transformer and resistors, voltage
regulator and wiring. All components are accessible
either by lowering the upper hinged panel or by
removal of the lower access cover.
cedures are included when applicable.
When plug P1 is connected, many of
the meters are still active and need
only a path to ground to complete
7-2. Frequence Converter
a. General. The frequency converter is located
near the center of the control box. It receives an
ac signal of 120 volts from one of the generator
coil groups and converts this signal voltage to a dc
voltage that is proportionate to the frequency of
the generator output. The frequency meter is fed
this.dc voltage and the meter indicates the output
frequency in Hertz.
Teat the frequency converter as
(1) Model MEP-071A.
(a) Apply AC input of 120 volts, 60
hertz current across terminals marked
(b) With panel (M3) connected to output
side meter reading should indicate 60 hertz +
(c) For teat with panel meter discon-
nected, direct output current of the converter
shall be 100 microamperes + 10 microamperes
with 1100 ohm load across positive and nega-
(2) Model MEP-022A.
With generator set
operating at 3428 rpm, remove screw in the
face of the frequency converter, and adjust the
potentiometer for a reading of 400 HZ on the
If proper reading is not
obtained, proceed as follows:
(a) Disconnect the lead from the positive
(+) and negative (-) terminals on the frequency
(b) Attach a multimeter with the scale
set to read at least 200 microampere, to the +
and - terminals on the frequency meter.
(c) Operate generator set at 3428 rpm
and turn adjusting screw to obtain a 100 micro-
ampere on the multimeter scale.
(d) If reading is accomplished, the fre-
quency meter on the control panel is faulty and
must be replaced.
(e) If reading of 100 microampere cannot
be obtained, disconnect the wire leads from the
two L terminals on the frequency converter,
Test the wire leads. If no defect is discovered,
replace frequency converter and operate generator
Turn adjusting screw to obtain 400 HZ
If frequency meter does not pass the
above test, replace it.
Refer to figure 5-1 and
replace the meter to the applicable model genera-
c. Removal. Refer to figure 7-1 and the follow-
ing instructions to remove the frequency con-