I have an old IRIS 4d/35 system with touchscreen capabilities and display is CRT type.

Recently we upgraded the system to run on LCD displays where we needed to provide the touchscreen controller with a separate power supply since the power for the controller was previously drawn from the CRT power supply.

However when a new switching power supply was used the touchscreen did not work. Reverting back to the supply from the CRT works flawlessly.

The supplies required for the touchscreen controller are 12V, -12V and 5V. The CRT power supply had a common ground and so does the new switching power supply.

Any idea what could be the problem with the new power supply. Any advise would be very much appreciated.