1st culprit I would be checking is the cartridge/cartridge wiring. You did not mention if you replaced it or not or what it was. And any of the other info in the 2 posts above should put you on solid ground, no pun intended till I had the thought.
apt holman problems
I recently bought a rega 25 and tons of albums -- the good news. The bad news occasionally the right channel cuts out and I reconnect everything and will try some connection cleaner. Now a hum has begun in the phono stage, seems worse on phono 1 than two. I don't have a manual, but might it be a ground issue? Is it worth trying to fix or is it time to get "tubed." Other components are Adcom 5500 monoblocks with Vandersteen 2ce's. thanks.