My Air Vac AV850 recently needed a replacement control board. Unfortunately the board is no longer available. This Air Vac is over 40 years old and I have replaced the twin motors two times as well as replacing the motor brushes a few times. Customer service for parts sites are useless in helping out. The original system was 220VAC and the motors are control via 110VAC.
I had an idea and wasn't sure it would work. I removed the 220VAC line and replaced it with a 110VAC power cord 12 gauge, plugged into a 20A outlet that is on a 20A circuit breaker. I removed the original board and bought a 110VAC board and installed it. Everything is working great now.
This is the new board: Vacuum Motor Circuit Board for Dual Motor / 28 amp 120v part # M-CB2MTR28A from Central Vacuum OnLine or Part #235L from Built-in Vacuum Systems MD.
This is my Air Vac and old control board:
