I think the model is a TLX. (Octagonal) Balboa control system. 115v (dual voltage model, powered by 115v). The pump is a 2 speed AquaFlo XP. The low speed works fine. When you select high speed there is a hum, higher current draw (the spa light dims slightly--I did not check with an amp meter), and the motor does not spin faster.
Thinking this was most likely a motor problem I took the motor to a local electric motor shop. They checked it out and said the pump/motor are fine. The cleaned up the switch inside while they had it, but proclaimed the motor is good.
So, now I get to troubleshoot the control board. I suspect a relay may be sticking, or something. My "day job" is in electronics, I have been a technician/engineer since the late 1970s so there may be some hope I can fix the board, not sure.
Any help and advice on this symptom would be greatly appreciated. Thanks!