After encountering a problem with saved scenes not being displayed, I wanted to initialise my desk.
Previously, this was done by holding PEQ in and HF, as described here:
Unfortunately, this somehow doesn’t work on the + series. Although this method is listed for both the old and new version of this desk, on the + it doesn’t have any effect.
To hard reset an Allen & Heath SQ+ model (such as the SQ-5+), turn off the mixer, press and hold the ‘LIBRARY’ and PEQ ‘HF’ keys simultaneously, and switch the power back on. Keep holding the keys until the unit fully boots up to clear all data and restore factory settings.