Connecting the degauss circuit.

If your monitor is an LCD, you don’t need to worry about degaussing and can skip this page.

If your monitor is a CRT, each time it’s rotated, the Earths magnetic field will distort the display, and it will need to be degaussed in order for the colors to be correct. Many monitors have a built in degaussing circuit you can activate via a pushbutton.  If your monitor does not have this function, you will need to devise your own way to degauss the monitor. You can still use LPT port pin 6 as a logic control if needed.

(There are a few sites that detail building a degaussing coil, you can check it out. You could use an SSR similar to the one used for the monitor on/off if AC power control is needed. Just check the current draw with a meter and size the SSR appropriately. If your monitor has an internal degauss coil, but it is only activated via an internal menu instead of a pushbutton, you may be able to disconnect the coil from the monitors control circuitry, and power it directly when needed)

If your monitor does have a pushbutton to activate the degauss, then we are in luck. We can use a small relay in parallel with the button to turn on the degauss function. 

For $2.37, DigiKey offers us this small reed relay . For this particular relay, connect pin 2 of the relay to pin 5 of the LPT port. Connect Pin 6 of the relay to any ground pin 18-25 of the LPT port. 

Find the degauss pushbutton switch for your monitor. There should be two contacts that short when the switch is pushed. You will need to solder a jumper wire to each of these contacts. One jumper wire will attach to pin 8 of the relay, the other jumper wire will attach to pin 14 of the relay. 

Please note that this relay is only designed to switch a logic level signal.    Use a meter to check and make sure the voltage across the degauss pushbutton in the monitor is  < 5v!!! 

You have now wired the relay in parallel with the button that activates the monitors degauss. When the relay is activated, it simulates you pressing the button.

More cheesy mspaint diagram action here: