I like to dive older Scubapro metal regs and my dive buddy is also catching the bug. He picked up a Mk5/R109 on ebay that really looked good. But a soniccleaning and new soft parts did not stop the slow leak thru the ambient chamber. Close inspection revealed a couple light longitudinal scratched in the piston o-ring seating surface of the ambient chamber (which still had most of its chrome finish intact). I verified the failure mode with an ambient chamber from another Mk5. With spare parts like that no longer available except from the junk yard, I decided to try to polish down the scratches to restore the sealing surface. I used some jewler's polish (Wright's Silver Cream) on the end of my finger and spent 10 minutes polishing the surface. (Careful, the ambient chamber threads may be sharp.) Worked like a charm and another Mk5 is back in service.
