GE 90-30 PLC Series Installation And Hardware Manual page 216

8
LED Indicators
Internal Fuse
The TCM's internal fuse is a 2 Amp, 125V subminiature type (Littlefuse Microfuse, Catalog
Number 273 002 or equivalent). If the P (External Power) LED will not light, the internal fuse may
be open. To access this fuse:
Automatic Data Transfers Between TCM and PLC
The PLC CPU controls the TCM by automatically passing commands to it on each PLC sweep.
These commands are contained in %Q bits and %AQ words that command such things as
Enable/Disable Output, Auto/Manual Mode, Do Autotuning, Setpoint values, and Alarm Limit
values.
In return, the TCM sends information to the PLC CPU by automatically passing %I bits and %AI
words each PLC sweep. The information sent by the TCM includes Alarm and Output Short
Circuit status, Current Temperature, PWM Period, and TCM Error Code.
8-38 Series 90-30 PLC Installation and Hardware Manual – August 2002
P (External Power) - This green LED is normally ON, indicating that the module is receiving
power. If this LED is OFF, it may indicate that the TCM's internal fuse is open.
R (Run) - This green LED is normally ON. When there is an internal module fault, this LED
will alternately flash with the red Fault (F) LED.
F (Fault) - This red LED is normally OFF. This light flashes upon module startup and goes
out when the TCM finishes its internal startup routine. When there is an internal module fault,
this LED will alternately flash with the green Run (R) LED.
S (Short) - This red LED is normally OFF. This LED lights when there is a short on one of
the output circuits.
1 – 8 (Output Status) - These green LEDs normally turn ON and OFF while the module is
regulating their outputs. The percentage of time that one of these LEDs is ON verses OFF is
representative of the PWM period of that output. Each of the eight LEDs corresponds to an
output channel. The output connector is the one on the right side of the module. The channels
numbers are labeled on the module next to the connector. For example, LED 8 corresponds to
the connections labeled 8+ and 8- on the right-hand connector.
Turn off power to the PLC, then remove the TCM module.
While gently pulling outward on the front cover, release the front cover side tabs with a small
("pocket-size") standard screwdriver.
Gently remove the fuse by pulling it forward, out of the front of the module, with a small pair
of needle nose pliers.
Replace fuse only with the correct size and type. Using an incorrect fuse can
result in harm to personnel, damage to equipment, or both.
Warning
GFK-0356Q