T O 35 C2-3-442-2
P-8-627-34
TM 5-6115-457-34
TM-07464A-35
R12, R14, R15, R16, and R18 full CW.
6-202. ON EQUIPMENT TEST
Measure resistance between points indi-
cated in table 6-20. Readings which do not
a. Symptom and Isolation of Malfunction.
agree with the values given in the table
A malfunction of the governor control unit
indicate a malfunctioning component in the
is usually indicated by loss of frequency
control unit and it should be replaced.
control, unstable frequency, or by instab-
ility only when operating sets in parallel.
2. Unstable frequency. - Refer to
To isolate the malfunction, proceed as
the alignment procedures (paragraph 6-211)
follows:
and check the adjustment of the magamp
bias gain R12, the load measurement gain
WARNING
R15, the frequency gain R18, and the feed-
back gain R16. If the above adjustments
Exercise extreme care not to
are correct, connect a DC voltmeter
touch exposed electrical connec-
(0 to 50 volt scale) across test points 1 and
tions when working inside precise
2 of the control unit. The voltage should be
zero at rated speed and should swing as the
operating.
frequency is varied above and below rated
speed by manually forcing the actuator
NOTE
linkage above and below its normal posi-
tion. If the readings are correct, check
Fold hinge cover away from pre-
the throttle position transducer circuit by
cise governor control unit to gain
measuring the voltage across test points 3
access to test points as shown in
and 4 (+) with a DC voltmeter. Operate
the set manually with connection P2 dis-
connected and move the actuator manually,
1. Loss of Control. - With the set
the voltage across TP3 and TP4 should vary
operating under manual speed control,
with actuator movement. Capacitor (C1)
measure the input voltage to the P1 connec-
can cause unstable frequency and should be
tion, pins A and B (nominal 120 VAC). Also
checked for a short or excessive current
measure input voltage to the P2 connection,
leakage. If the cause of this unstable fre-
pins A(+) and B(-) (20 to 32 VDC). If the
quency is not located by the above checks,
control unit is properly energized, measure
perform the resistance checks listed in
the voltage at test points A to B and C to D
with A and D(+) (4 to 6 VDC). If either volt-
readings when the adjustment potentiom -
age is approximately 15 VDC, check for an
eters are turned. Also check the resistance
open circuit to the actuator coils. The
of all pins to ground with an 100, 000 ohm
actuator coil resistance should be 10 ohms
scale. All readings shall be infinite resis-
10%. If there is no voltage, the control
tances. Readings other than those speci-
unit should be replaced. If the above read-
fied indicate replacement of the control unit.
ings are correct, check the circuit to the
frequency adjusting rheostat (R1) on control
3. Instability when operating in
cubicle from the PI connection. Pins N to
T should measure 950 ohms 10%, pins M
parallel. Check this setting of the load
sharing potentiometers (R28). Both units
to N and M to T should measure 750 ohms
should be set at 4.6 0. 25 volts with Pi-G
10%. If the above checks have not indicated
the malfunction, disconnect all cables from
positive (pin A of the paralleling receptacle).
the control unit, rotate potentiometers R11,
Also the frequency gain (R18) and feedback
Change 8
6-162
