This guide is intended to help users understand the L4 and L2 inductors that are fitted to the CP-11's and CP-10's.
This article will explain how the inductors compatibility with different backplane voltages, how to identify them on their above mentioned processors and potential fixes that can change the compatible input voltage supported on the board.
Issues with voltage incompatibility:
The location of inductors that are installed on your CP-11 and CP-10, will determine whether or not the board is compatible with the voltage on the backplane.
The L4 inductor allows for voltages at 24V to function on your CP-10/11 processor. The L2 inductor allows for voltages at 12V to function on your CP-10/11 processor.
Hence if you have both inductors installed, you board will be able to support both 24V and 12V inputs.
This can be determined by looking at your boards and determining whether or not the L4 and L2 inductors are installed. See below for examples.
Above you can see a CP-10 with both the L2 and L4 inductors installed. Meaning it is compatible with both 24V and 12V backplanes.
Above you can see a CP-11 that only has the L2 inductor installed, hence it will be only compatible with a 12V backplane. A 24V backplane will not function correctly on this particular board.
How does it work, and how can I modify it?
The L4 and L2 inductors are connected to different resistors respectively, which drop the voltage down to the boards preferred 5V.
These resistors have different values in order to correctly drop down the voltage to the correct value.
This does mean that it is possible to modify this board to convert it from a 24V to 12V compatible board, and vice versa.
The inductor model in these pins are the same. Hence by un-soldering one inductor and re-soldering it to the other L4/2 pin location, you can change the input voltage the board can support.
Note: If you proceed to modify your boards by performing this fix, you will void any warranty covered on the boards.