Supply Is - GE 90-30 PLC Series Installation And Hardware Manual

13
Module LED Indicators
Input Module LED Indicators
When a discrete input device closes, the corresponding input LED should light to indicate that the
signal reached the module. If the light does not turn ON, a voltage check can be made on the
module's terminal board or block:
If none of an input module's inputs are working, it may be that the external (field) input power
supply is defective, not powered up, or not connected properly. (Input and output devices are
powered from an external power supply, not from inside the module). Input modules are not fused,
so the Fuse Indicator LED in the previous figure does not apply to them.
Output Module LED Indicators
When a discrete output address (%Q) is turned on in the ladder program, the corresponding output
LED should light to indicate that the signal reached the module.
If none of an output module's outputs are working, it may be that the external (field) output power
supply is defective, is not powered up or is not connected properly. (Input and output devices are
powered from an external power supply, not from inside the module). If the output module is a
type that has built-in fuses (some have electronic short circuit protection instead), the Fuse
Indicator LED (labeled "F"), shown in the previous figure, will light if a fuse blows.
Power Supply LED Indicators
The power supplies have four LED indicators. Their functions are explained in the "Power
Supplies" chapter.
CPU LED Indicators
There are several different LED arrangements on the various CPUs. These are explained in the
"CPUs" chapter.
Option Module LED Indicators
There are numerous LED arrangements on the various option modules. The "Option Modules"
chapter has some information on this subject. It also directs you, for each module, to further
information in the "Documentation" heading for each module. Also, Appendix G contains a
catalog number to documentation cross-reference.
13-2 Series 90-30 PLC Installation and Hardware Manual – August 2002
If the correct voltage is present at the terminal, the corresponding input bit can be checked in
the PLC with your programming software. If the software shows that the input bit is at logic 1,
the module's LED circuit is defective.
If the correct voltage level is not present at the terminal, a check can be made at the input field
device to determine if the device or interconnecting wiring is defective.
If the light does not turn ON, the module may be defective or the LED light may be bad.
If the light turns on but the output device doesn't operate, a voltage check can be made on the
module's terminal board or block. If the correct voltage level is present there, the output
device or wiring should be checked.
GFK-0356Q