It's normal that all records to have 'psc_mod' field empty. This is only changed only for newly added device templates or for those who are changed. It looks like you didn't add the device template at all.
Please try again, following this steps:
- go to A/V equipment;
- choose add device;
- select the manufacturer and the device category (both are displayed on top of the page, just under "manufacturer" and "device category" titles;
- click "add", the button on top of the page;
This should open a wizard who will allow you to add and setup your device template.