Hello all. I recently purchased a new Shen SB180. The bass has a good set up, and sounds great (for what it is) but the tuning machines have to go. The D key slips, due to the key not being close enough to the gear. It stays in tune but when tuning down, the key slips. You have to go under pitch, then back up, to avoid rattle. I m guessing this is a standard size Tyroleon type tuning machine. I plan on getting new ones soon, but want to make sure the new set interchanges easily. Does anyone have suggestions on sets in the $200-$400 range? Any one else suffering from slippery keys?