Turntable Hum And Channel Drop

I got a new Origin Live Silver tonearm for my SOTA Star turntable about six months ago and it sounds great.  About two weeks ago I noticed a faint hum, but wrote it off as HVAC noise from the neighbors house.  The hum grew ore noticeable a few days ago, and now the left channel fades out at about 1 1/2" into the record, and returns at about 2 1/4"  I raised the tonearm with the motor on and moved it over the top of a record ,and can hear the hum increase and decrease in volume as the tonearm moves over the record.  I checked all of the connections and they are fine.  I swapped RCA cables from left to right and the channel drop then goes to the right channel.  Grounds are all snug.  Any thoughts on what's going on? 

For the record I have a Hana EL cartridge and a Jolida JD-9 phono amp.  Thanks in advance for your input.