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(3)  
A dedicated winding in the EEC alternator supplies a frequency proportional to the N2 speed to the engine (N2) speed card.

 (4)  
The EEC monitors N1 and N2 parameters along with various other inputs to maintain engine performance.

DM7353
M7353 EIU-3

DM7352
M7352 EIU-2

CH A
DM7198B
DM7351

CH B
CH B
M7351 EIU-1

M7198 ELECTRONIC EEC SPEED ENGINE CONTROL TRANSDUCER (N1)E2-6 EIU RACK
N1 Indicating Simplified Schematic
Figure 3

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E47376
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M7603 ELECTRICAL SYSTEMS CARD FILE

YMLA001-ENG 1 YMLA003-ENG 2 YMLA005-ENG 3 YMLA007-ENG 4
N2 Indicating Simplified Schematic Figure 4
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ENGINE TACHOMETER SYSTEM - ADJUSTMENT/TEST
__________________________________________
 1.  General
_______
 A.  This procedure includes the task to do an operational test of the engine
 tachometer system.

 B.  To do the operational test, you must operate the engines.
 C.  Do the operational test to make sure the system operates correctly after
 you replace these components:

 (1)  
The EEC Speed Transducer (N1)

 (2)  
The EEC Alternator (N2 transducer).

 TASK 77-12-00-715-003-N00
 2.  Engine Tachometer System Operational Test (Fig. 501)
_________________________________________
 A.  References
 (1)  
AMM 24-22-00/201, Manual Control

 (2)  
AMM 31-61-00/501, Integrated Display System

 (3)  
AMM 32-09-02/201, Air/Ground Relays

 (4)  
AMM 71-00-00/201, Power Plant

 (5)  
WDM 73-21-71, 73-21-72, 73-21-73, 73-21-74, 77-12-21, 77-12-22

 (6)  
WDM 77-12-23, 77-12-24

 (7)  
SSM 73-21-08, 77-12-21

 B.  
Access

 (1)  
Location Zone
 221 Control Cabin, LH
 222 Control Cabin, RH

 C.  
Preconditions

 S 865-008-N00
 (1)  
These conditions are necessary for this task:

 (a)  
Electrical power on (AMM 24-22-00/201).

 (b)  
Integrated Display System serviceable (AMM 31-61-00/501).

 (c)  
Airplane must be in the Ground Mode (AMM 32-09-02/201).

 (d)  
The engine must be operational (AMM 71-00-00/201).

 D.  
Procedure

 S 865-001-N00
 (1)  Operate the engines at the same power.
 (a)  
Start the engines (AMM 71-00-00/201).

 (b)  
Make sure these engine parameters become stable and are approximately the same value: 1) EPR 2) EGT.

 S 715-004-N00
 (2)  
Make sure the N1 indication on the main EICAS display is
 approximately the same for each engine.

 S 715-005-N00

 (3)  
Make sure the N2 indication on the auxiliary EICAS display is approximately the same for each engine.

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