[Zope] Getting Zope code to output to event.log

To debug my code in my Zope/Plone site, I sometimes need to put logger lines into Zope/Plone code, in order to trace my way through an error traceback. I can do this easily with Plone code in the Plone Products folder: Just put in the logger line, restart Zope, run my tests, and the output appears in the Zope event.log. But when I try the same thing with native Zope code (for example, in the OFS directory), the output doesn't show up in event.log. I figure these modules have to be reinstalled or re-somethinged to get my changes activated, but I don't know how to do this. Can you help? ~ TIA ~ Ken