I had this problem just after I purchased my pre in 2018. Didn’t correlate an hr/reset time for it to correct and then happen, again, but reading your description it’s definitely the same symptoms. Service dept sent me a replacement microprocessor, updated firmware, tool, anti-static strap and instructions. Seemed to do the trick, however, I do get the same intermittent problem @jamesh experiences. I’d say I’m 97% fixed but it does happen on occasion and I’ve lived w/it.
At first, I phoned the service dept, followed by the following correspondence when I was troubleshooting. Read as most current email first w/older as you scroll. There are references to other threads, too.
From: Mark Simpson
Sent: Thursday, February 21, 2019 09:42
Subject: RE: BHK Signature Pre Volume Problem
As we discussed, I’ve initiated a zero dollar Sales Order for a new Preamp Firmware Upgrade. You should have that in 3-5 business days.
Sent: Thursday, February 21, 2019 10:16 AM
To: Mark Simpson
Subject: BHK Signature Pre Volume Problem
…I received a replacement microprocessor and I swapped it out approx. 1 month ago. Been on the road and finally able to follow-up w/you guys. Microprocessor did not fix the problem and it persists.
Following posts are from the original PSA Forum thread I found when this first started researching this.
Complete thread: https://forum.psaudio.com/t/bhk-pre-amp-problem/
These 2 posts are the exact symptoms I’m experiencing:
Jun '17 I just started having my own problems. The preamp started normally this evening but when I tried to change the volume with the remote it didn’t move. I rebooted the preamp and the 45 second warm-up countdown took four or five times that long. When it eventually came on, it had the same volume problem. If I spin the physical volume knob it sometimes moves a click or so per revolution (or two or three revolutions). I unplugged the unit for 15 minutes and rebooted. Same thing. 45 second countdown took over five minutes. Volume knob mostly unresponsive and remote totally unresponsive, including input changes (inputs can be changed from front panel). It is not in Home Theater mode.**
Jun '17 I’ve had a similar problem(s) with my BHK preamp… Both times it was the small board/microprocessor that the stepper motor is attached to… First fault: a failed display - burnt-out component. ( Dave P sent me the parts and I installed the board and display and all was well for a few months ) Second fault: unresponsive volume ! ( Dealer sent me the new microprocessor and the musical bliss resumed ) …"
…Edited for format.