Hi Mike, I don’t know if you are still interested. But if you download the service manual from Vinly Engine, here, you can see what you need to do. You have to take off the mat and platter and then remove the bottom board to get to the circuit board. The knobs are on the board that is connected to the rotor assembly. You can read what another poster did to adjust the speed by trial and error: viewtopic.php?f=18&t=71108
That is what I did and I got the turntable to 33.31 according to my iphone app. But using the printed strobe disc, I think it is right on 33 1/3.