I highly recommend AGAINST powering your control panel from a lab power supply or other source. Also do not add any circuitry between the opener and control panel like a linear voltage regulator. Those two wires are NOT just power, they are power AND a 2 way communications network. The control panel is expecting a specific source impedance and voltage from the opener. The control panel uses the available power for it's operation, but it also shorts out it's own power supply to provide digital communications back to the opener, signaling the opener to perform certain functions like open your door. It also monitors the power supply for communication data from the opener. Placing any circuitry between the opener and control panel will block this communication.
I have a 3800 and a 3900. After one control panel failure of "phantom opening" I removed both wall units and installed doorbell style push buttons. I briefly looked at reverse engineering the communications protocol, but soon lost interest.
For people with 8500 openers or others openers where the vehicle remote receiver is built into the control panel and are experiencing repeated failures, I might suggest a workaround.
Liftmaster and others sell a "receiver" that is designed to add remote functionality to commercial garage and gate openers that do not have remote functions. These receivers simply have a relay that acts just like a momentary push button. Thus, throw your control panel in the trash, install a doorbell for manual operation, then the receiver to add vehicle remote functionality.
I've been using the 850LM on one of my commercial openers for 4 years now.
https://www.northshorecommercialdoor.com/li85ungaandg.html
Brian