I recently purchased a Grizzly G0634XP planer/jointer combination unit. I was using it yesterday, and when in the planer mode, there is a sound that I believe is the planer's chain slapping something. The sound is not present when used as a jointer. There appears to be a great deal of slack in the chain. I've looked through the instructions, and can't find an explanation for how to tighten the chain. I was wondering if anyone had any thoughts?