TUBE ASSEM. 7P7976 - Caterpillar

The MCM Panel has two connectors that can be used to provide power to the panel. The leftmost connector, A-C5, is where the panel receives the Primary Power Source, and the rightmost connector, A-C6, is where the panel receives the Secondary Power Source. The pinout of A-C5 and A-C6 is shown here. The mating connector is Cat part number 172-3998 Plug As .The power sources on A-C5 and A-C6 are redundant to the MCM panel. If one of the power sources fails or is disconnected via one of the power source breakers or one of the keyed switches on the front on the panel, the MCM panel will continue to operate using the other power source if the other power source is operational.Each power source should meet the constraints in Table 1:
Table 1
Power Source Specifications    
Constraint    Value    Unit    
Voltage (range)     19.2-26.4     VDC (Volts DC)    
Voltage (range) (1)     8-32     VDC (Volts DC)    
Current (minimum)     10 (2)     A (amps)    
( 1 ) At this voltage, the MCM Panel will function, but operation and integrity of the remote/local status relays are not guaranteed
( 2 ) Minimum current does not take into account the current required for the load sharing module or other external devices powered from the terminal blockKeyed Switches and Indicators
The front of the MCM panel has a keyed switch and a light indicator for each of the primary and secondary power sources. When closed ("on"), the keyed switches provide power to the component power breakers from each of the power source breakers. When power is supplied to the component power breakers, the light indicator illuminates green.Power Source Breakers
There are two power source breakers that disconnect power from the entire MCM Panel. Power is only removed from the MCM Panel if both breakers fail to conduct current (either by a tripped breaker or a failed power source to the breaker). Each of the power source breakers corresponds to either primary or secondary power source, keyed switches, and indicators as follows:
Primary power: A127
Secondary power: A129Component Power Breakers
The component power breakers receive power from the power source breakers when a keyed switch corresponding to an appropriately wired power source is in the ON position. The component power breakers serve the components as follows:
Table 2
Power Breakers    
Component    Breaker    
Master MCM     A130    
Slave MCM     A128    
Internal Signal Converters     A130 or A128 (when either or both is powered, the converters are powered)    
Load Sharing Module Supply (Term Block A113)     A113    Power Circuit Schematic
Illustration 7 g03280957
Power circuit schematicField Wiring
Terminal Blocks
Many signal connections are made via the terminal blocks. Each terminal block has 4-spring loaded contacts for easy insertion and extraction of wires. A wire is inserted into and extracted from the round holes by inserting a short, flat blade screwdriver into the square hole. Refer to Illustrations 8 and 9 for the field connections on the terminal blocks.
Illustration 8 g03279817
Terminal block (top half)
Illustration 9 g03279818
Terminal