How to adjust the bias on an Audio Research Ref 75?

I've jumped into the tube world in the last 30 days with purchasing a Ref 6, PH7, and now the Ref75.  The sound is just superior to what my AudioControl Maestro M9 powered by a Parasound A31 could ever produce.

Yesterday, I checked the bias reading on the tubes and only one is sitting at the 65 mark.  So I pulled off the cover and read the manual but I'm lost.  Where is the bias adjustment screw?

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@cleeds Thank you so much!!!  We are sitting pretty now across all four tubes at 65.  

Eva Cassidy is sounding angelic right now. 

Congradulations! Being a real fan of the wonderfully natural and musical sound of Audio Research. I know what you are experiencing. That combination has the sound that draws you in and involves you in the music (instead making you listen to the system). I listen to mine two to three hours a day and have to drag myself away when I need to go.