Hi, Hope you were able to revive the G68!
The 5.2V made my volume knob more responsive, so for me a worthwhile tweak.
You can also power it down, take off the power lead. Adjust the pot meter a little, power it back on and then check voltage. But in the end you'll be measuring with the voltage on, so I just tweaked it while the power was on. You just need to be a little careful, but as there are no open 230V wires, you should be fine unless you are really clumsy smile.
Bas

Meridian G68 AXV, HD621 | Cinepro 2k6mk5 | 4x Scanspeak A4 monitors, center & 26W Sub | RPi Hifiberry digi+ | Roon