I recently serviced this Seiko 6139-7070 vintage chronograph for a regular ClockSavant customer. The watch has many positive attributes including a case in unusually nice condition, but it experienced the dreaded vertical clutch failure that can happen with any vertical clutch-based chronograph including the Seiko 6138 and 6139. The most common cause is that a past watchmaker damaging the clutch by putting it in cleaning fluid. The general rule with many vertical clutch designs is that they are permanently lubricated at the factory, cannot be disassembled, and are best not cleaned because the cleaning process can promote “freezing” them by removing lubrication and replacing it with sticky cleaning fluid residue inside the sealed areas. The symptom of damage is very low amplitude (strength of balance swing is low) when the chronograph is off (or watch stops), and when you turn it on thereby releasing the friction inherent in the clutch design, the amplitude jumps to a much higher number. With a few rare exceptions, the supply of these clutches dried-up sometime ago. Fortunately, I had a donor movement with a good vertical clutch and was able to bring the watch back to excellent performance. Next on the list of items was an intermittent “stuck reset” pusher. The cause here, as shown in the magnified picture, was a rough spot on the tension spring used to “push-back” on the reset pusher. I was able to supply a replacement plate for this watch. While the watch would have benefited from a new crystal, some customers like older crystals even if they are scratched and such was the case here. The watch is now running very nicely and ready for its new future.
