24-21-00
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A
737-300/400/500MAINTENANCE MANUAL
 S 975-112
 (7)
Read and record the duty cycle displayed on the multimeter.

 S 835-113

 (8)  
Shut down the engine.

 S 975-114

 (9)  
Calculate the direction and number of VSCF voltage regulator adjustment screw turns to achieve a duty cycle of 24% +/- 1% using the following data. Each turn changes the duty cycle by approximately 8%. Counter clockwise turns increase the duty cycle.

 S 015-115

 (10)
 Open the engine cowl.

 S 015-116

 (11)
 Gain access to the VR dajustment screw on the VSCF unit.

 (a)  Turn the adjustment screw accorcing to the calculations.
 S 825-117
 (12) Start the engine and make sure the adjustment is correct.  If the adjustment is not correct adjust the VR again.
 TASK 24-21-00-705-118
 5.  Bus Transfer Interlock Test____________________________
 A. General
 (1)  
The purpose of this test is to check the intergrity of the bus transfer interlocks provided by the auxiliary contacts of the Main Power Circuit Breakers. Transfer times of approximately 8 to 12 milliseconds indicate correct behavior of the interlock and the intergrity of the associated airplane wiring. Transfer times of approximately 4 milliseconds would indicate the loss of the appropriate interlock due to either 1. a malfunction of the auxiliary contact in the contactor being transferred FROM or 2. a short in the associated wiring which bypasses the auxiliary contact. This condition by itself would not result in paralleling sources but if coupled with a contactor slow to drop out by an additional 4 milliseconds or more, parralleling would be expected.

 (2)  
The test checks each phase during transfer thereby providing three checks of a particular type of transfer. If intermittent operation is suspected then wire wiggling at the contactor connectors in conjunction with the transfer test may be warrented.

 B.
Equipment

 (1)  
Tektronix portable Oscilloscope THS 720, THS 732 or equivalent oscilloscope which can trigger on power interruptions.

 C.
Procedure

 S 865-119
 (1)  Apply electrical power to the airplane using all electrical power sources (AMM 24-22-00/201).
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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737-300/400/500MAINTENANCE MANUAL
 S 865-120
 (2)  
Connect the oscilloscope to the AC contact of the M400 module.

 S 725-122

 (3)  
Set the M400 switches to the appropriate main bus and phase as follows:

 (a)  
BUS 1
 Phase A -A1
 Phase B -B1
 Phase C -C1

 (b)  
Bus 2
 PHase A -A2
 Phase B -B2
 Phase C -C2

 S 975-123
 (4)  Measure and record the transfer times for each main bus for the following transfers:
 (a)  EXT to APU to GEN to EXT to GEN to APU to EXT.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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737-300/400/500MAINTENANCE MANUAL
 AC ENGINE-DRIVEN GENERATOR - REMOVAL/INSTALLATION
_________________________________________________
 1.  General
_______
 A.  This procedure has two tasks. One task is the removal of the ac engine-driven generator (G1). The other task is the installation of the generator.
 TASK 24-21-11-004-002
 2.  AC Engine-Driven Generator Removal (Fig. 401)
__________________________________
 A.  Special Tools and Equipment
 (1)  F80011-1 or F70333-1, Cradle Adapter Assembly, AC Generator and Constant Speed Drive (for supporting CSD and/or generator during removal/installation)
　
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