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Good day, I have a strange situation - I have restored a non-running Seiko 7S26A and thought I had done a great job Rate <5 s/d Amplitude >220 degrees Beat Error 0.1 Hands move in sync Day/Date changes correctly Then I notice that the second hand continues to make one revolution every 60 seconds BUT the hour and the minute hand barely move over the course of a day. I pull the crown and both hands move smoothly and correctly. Then once I push the stem back in again the second hand ticks correctly but hour and minute hands are VERY slow. Timegrapher still shows watch is working well. Obviously the train of wheels/balance etc are working well as the watch seconds hand is ticking correctly, and the watch is performing well on the timegrapher. The hour and minute hands are installed correctly and not fowled as I can move them easily and in sync with the winding stem/crown. So what could be stopping/slowing the minute and hour hands from moving correctly (min hand moved 5 mins in about 12 hours), but still allowing the seconds hand to move at the correct speed (60 seconds in 60 seconds) and the watch to perform well on the timegrapher and visual confirmation that the balance/escape wheel/pallet fork are moving well? This has me baffled and I have taken the watch apart/cleaned and re-built with the same result... feel like I'm losing my mind as I don't see how these things can be happening at the same time! (pun intended)
Seiko 7S26A Complete Service Background I have a good friend, a brother in Christ Jesus, who I've known for many years. He knows I've embarked on retraining myself for a new career in Watchmaking, and seen my first two restored watches. He told me that his old faithful Seiko 5, which he's worn everyday for 12 years, has recently had issues. Occasionally it will advance rapidly in time (up to an hour in a few seconds) and then just keep ticking away normally. I told him I'd be happy to take a look at it, and put it on my ACEtimer Timegrapher. The pattern on the screen looked like a B-52 drop in Nam (stupid me forgot to take a photo), and I told him that his watch definitely needed an inspection and service. So started my research on what the problem might be. After reading a "Practical Watchmaking", and the many forums that I've read, I was pretty sure it was the Pallet Fork ... either very dirty or damaged stones, or a broken/damaged fork pivot. So onward to the service... Disassembly One unusual aspect of this watch is the crown ... or lack there of, more to the point. I suppose since this is an automatic watch, they thought it didn't need to be wound. This watch also has a display back, so extra special care not to mark any of the plates, or damage screw heads! The first issue you'll face when working on a 7S26A Movement, is how to get the stem out! It isn't obvious at all, and there is a little trick. The crown needs to be pushed all the way in to expose the push plate (it is hidden in the other crown positions). I took this photo once the movement was out to best illustrate where to push. Remove the Hands, Dial and Oscillating Weight (2.0mm Screwdriver). Gently lever up one end of the circlip and carefully work your way around. You then should be able to raise the circlip up the length of the shaft without it pinging off. Remove the Day Wheel and the four screws holding the Date Dial Guard. (Use a 1.40mm Screwdriver, and this driver is good of all the screws from now on; bar one.) NOTE ORANGE ARROW: Seiko Special Tool needed for the 0.98mm Philipshead Screw (Part Number: S-921) I had to journey down to my nearest Seiko Distributor and grab one ... cost was AU$24.00 Here's a closer look at the troublesome screw. Remove Date Jumper, and note that the Date Drivewheel lips over the top of the plate. Remove all the motion work, and pull the Cannon Pinion Remove the tension from the Mainspring. Remove the Ratchet Wheel and the Second Reduction Wheel and Pinion. (remember the Reduction Wheel has a reverse thread) Unscrew the Balance Cock and remove the Balance. Also unscrew the Pellet Cock and remove the Pellet Fork. BINGO! Found the problem with my friends watch. The top pivot on the fork is broken. Easy fix with a replacement fork :) Remove the Barrel/Train Wheel Bridge Remove the Click, then the Barrel. Remove the Fourth Wheel, Third Wheel and Escapement. Unscrew the Centre Wheel Bridge and remove the Centre Wheel Now to the Keyless Work. Remove the Setting Lever Spring Remove the Yoke and the Setting Lever Pull the Stem out, and the Clutch and Intermediate Wheel will fall away. Lastly, pull the black plastic location ring off. ... and now it's bath time!!! I hope this has been of help to you guys. I'll post the Assembly steps in this thread tomorrow morning.