Initially, I replaced the speed governor and speed control plate. That did not help. Then I replaced the phase control board and that fixed the problem. I was able to calibrate the mixer so slow speed (lever position 1) was running at ~60 rpm and medium speed (lever position 6) was ~180 rpm. Good as new.
Even with buying the two unnecessary parts, I was still only into this less than $50 + shipping - beats buying a new mixer.