Relative to hissing sound.
Folks the pmc8 drives the motors 100% of the time, even when the mount is sitting still. Wait, what? Yep. The motors are stepper motors and are always energized. The current into them is pulsing on and off (42,000 times per second), it’s the nature of the beast. So they make noise. And the noises are variable. So noise ordinarily does not equal issue. Now if the mount is moving in an abnormal fashion and making a racket you have something going on, generally binding on an axis.
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired