(b)
Open the two generator circuit breakers C801 and C802
NOTE: You will find the circuit breakers on the outboard
____ side of the nose wheel in the right forward compartment.
(c)
Open the two APU generator circuit breakers C889 and C890 on the P6 panel.
(d)
Open the generator control circuit breakers C4, C5, and C6
NOTE: The circuit breakers are found in the load control
____ center (P6-4) on the right side of the airplane.
(e) Measure the exciter field resistance between terminals A and F.
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(f) If the field resistance is not between 6.7 and 9.0 ohms, replace the ac generator.
(3) A rotating rectifier failure.
(a)
Make sure that the generator turns. 1) Operate the engine with the generator control relay open. 2) Measure the residual voltage of the generator.
a) You must find 12 to 19 VAC between the terminals T1, T2, and T3 of the voltage regulator and ground. 3) If you do not find the correct voltage, replace the ac generator.
(b)
Make sure that there are no open or short circuits in the exciter field. 1) Open the generator control relay (GCR). 2) Open the circuit breakers C801 and C802 for the generators.
NOTE: You will find the circuit breakers on the
____ outboard side of the nose wheel in the right forward compartment.
3) Open the circuit breakers C889 and C890 for the APU generators.
NOTE: The circuit breakers are found on the P6 panel.
____
4) Open the generator control circuit breakers C4, C5, and C6
NOTE: The circuit breakers are found in the load
____ control center (P6-4) on the right side of the airplane.
5) Measure the exciter field resistance between terminals A and F.
6) If the field resistance is less than 8 ohms, replace the ac generator.
(c)
Make sure that the voltage regulator operates correctly. 1) Install a GCU that has a known good voltage regulator. 2) If the circuit operates correctly, replace the defective
GCU.
(d)
ENGINES WITH A CSD; Do this task: "Generator Rotating Rectifier Test" (AMM 24-21-61/601). 1) If the rotating rectifier is defective, replace the ac
generator.
(4) The generator feeder wires have a short circuit.
(a) Disconnect the generator feeder wires from the T1, T2 and T3 terminals on the generator.
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(b) Use an ohmmeter to examine the feeder wires for continuity.
NOTE: Measure all of the wires phase to phase and phase to
____
neutral.
1) If you find continuity between the wires, replace the applicable wire.
I. ENGINES WITH A CSD; The Constant Speed Drive
(1) An input shaft or a generator shaft failure, or the generator will not disconnect.
(a) Make sure that the constant speed drive is connected to the gearbox.
NOTE: If the CSD is disconnected, do the CSD Inspection/
____
Check (AMM 24-11-11/601).
(b)
Operate the engine with the generator control relay open.
(c)
Measure the residual voltage to makes sure that the generator turns. 1) You must find 12 to 19 VAC between the terminals T1, T2 and
T3 of the voltage regulator and ground.
(d)
If the CSD is connected and the residual voltage is zero, the input shaft or the disconnect unit is defective. 1) Replace the CSD.
(e)
If the low oil pressure light is off and the residual voltage is zero, the generator shaft is defective. 1) Replace the generator.
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