(2)  
Access Panel
 P180 DC Power Distribution Panel

 C.
Install the DC Bus Isolation Relay

 S 424-027
 (1)  
Install the relay:

 (a)  
Put the relay in its position on the P180 panel.

 (b)  
Install the two screws that attach the relay to the panel.

 (c)  
Tighten the screws.

 S 434-028
 (2)  
Connect the electrical leads to the relay:

 (a)  
Remove the screws that attach the terminal cover to the relay.

 (b)  
Remove the terminal cover.

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 (c)  Remove the nuts and the washers from the terminal studs on the relay.
 CAUTION: MAKE SURE YOU CONNECT THE CORRECT ELECTRICAL LEAD TO EACH
_______ STUD ON THE RELAY. AN INCORRECT INSTALLATION CAN CAUSE A MALFUNCTION OF THE CIRCUIT AND DAMAGE TO THE EQUIPMENT.
 (d)  Connect the electrical leads to the terminal studs on the relay.
 CAUTION: DO NOT INSTALL THE WASHERS BELOW THE ELECTRICAL LEADS.
_______ THIS WILL CAUSE HEAT THAT CAN BURN THE STUDS ON THE RELAY.
 (e)  
Install the washers and the nuts on the terminal studs.

 (f)  
Tighten the nuts.

 (g)  
Remove the identification tags from the electrical leads.

 (h)  
Put the terminal cover in its position on the relay.

 (i)  
Install the screws that attach the terminal cover to the relay.

 (j)  
Tighten the screws.

 S 414-018
 (3)  
Close the access doors for the P180 panel.

 S 864-032

 (4)  
Connect the electrical connectors to the batteries:

 (a)  
Put the main battery connector (DM7423A) into the receptacle on the main battery.

 (b)  
Put the APU battery connector (DM7432A) into the receptacle on the APU battery.

 (c)  
Turn the knobs on the connectors clockwise with your hand until they are tight.

 D. Do a Test of the DC Bus Isolation Relay
 S 864-020
 (1)  
Supply electrical power (Ref 24-22-00/201).

 S 714-029

 (2)  
Do a test of the relay:

 (a)  
Get access to the EXISTING FAULTS page for Chapter 24 (if any) on the CMCS (AMM 45-10-00/201).

 (b)  
Make sure the CMCS messages for the applicable DCIR do not show.

 (c)  
Push the applicable BUS TIE switch, on the P5 panel, for the DCIR that was replaced.

 (d)  
Make sure the ISLN light on the BUS TIE switch comes on.

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MAINTENANCE MANUAL

 (e)  
Get access to the EXISTING FAULTS page for Chapter 24 (if any) on the CMCS (AMM 45-10-00/201).

 (f)  
Make sure the CMCS messages for the applicable DCIR do not show.

 (g)  
Push the BUS TIE switch.

 (h)  
Make sure the ISLN light on the BUS TIE switch goes off.

 S 864-030
 (3)  Remove electrical power, if it is not necessary (Ref 24-22-00/201).
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747-400 MAINTENANCE MANUAL
 APU TRANSFORMER RECTIFIER UNIT - REMOVAL/INSTALLATION
_____________________________________________________
 1.  General_______
　
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