Threshold NS10 Preamp Repair

I have a Threshold NS10 which I have had for 30 years.  I only use it as a phono stage, most recently for my VPI turn table.  I have always loved that preamp.  It's such a musical yet invisible phono stage.  I've recently noticed more hum emanating from it when the volume is turned up and nothing is playing. There is also now a pop when I turn my VPI motor pod off and forget to turn down the volume on the preamp, which isn't connected to , or powered by the same circuit.  I am thinking it's time for it to be gone through and possibly repaired if need be.  I was hoping I could get some guidance on who might repair these (I hate to say vintage because that makes me vintage) old Nelson Pass Threshold NS10's.  Thanks in advance for any ideas on the issue and/or recommendations on a repair place.  I live in the SF Bay Area if anyone knows of someone local.  Thanks.