The autoweight on a 7S26 will not spin like a top when the ms is fully powered. You should be able to visually determine that it is advancing the ratchet wheel at low power and when fully wound (causing the bridle to slip). Also, you should be able to determine if the autoweight is impinging on the movement or case back due to wear or incorrect mounting/spacing/caseback gasket.
If you were able to remove/service the mainspring, you are better than most...these are sealed barrels, not designed to be serviced. BTW, did you use braking grease on the barrel? Seiko loads these up with a nasty moly lube...but I get better results lubing barrel wall only (with braking grease) and leaving the ms clean & dry.
Diagnosing PR-7S26:
Remove the back. Remove the rotor. Remove the Second Reduction Wheel (careful…screw is left-hand thread. Turn CW to loosen…once slightly loose, disengage the pawl lever fingers, then completely loosen and remove the Second Reduction Wheel…this should prevent launching the SRW across your bench). With a screwdriver, put full power on the mainspring by turning the ratchet wheel (screw) 10 full turns (only 6-7 should be required…so 10 insures full power).
Now see how much power actually have on the mainspring. Use a screwdriver to control let-down of the mainspring ½ turn at a time (using tweezers) to alternately hold the click back to let down the ms, then re-lock. Count the number of turns to fully deploy the power. For the 7S26, it should be 6-7 turns. If 5 turns or less, you may have a worn barrel, broken mainspring, or braking grease issue. This barrel is sealed…designed to not be cleaned/opened…only replaced…and the replacements are now obsolete…and there was never a replacement mainspring listed.
Now see how what your PR is on a full wind: Put 10 turns of power on the mainspring. Close the watch (without the second reduction wheel & rotor)…set the date and time (and make note). Let the watch run until it stops. Determine how long the watch ran. If 40 hours or more, performance is probably adequate.
Check remaining power: Remove the back. Use your screwdriver and tweezers to let down the remaining power on the mainspring. If more than ½ to 1 turn of power remains and the watch is stopping, you very likely should service the movement (which is preventing full deployment of the ms power).
Finally, check the autowind: Fully power the mainspring (10 turns on the ratchet wheel screw). Reinstall the Second Reduction Wheel (careful to get the pawls back into position on the SRW). Reinstall the rotor. Now rotate the rotor with pegwood/toothpick and verify that the ratchet wheel is advancing. If the rotor will not drive the ratchet wheel at full ms power, you may have an issue with the pawl lever finger condition or Second Reduction Wheel teeth. If this action drives the ratchet wheel, then rotor should be able to fully power the ms.
Finally…how many turns of the rotor (from zero power) to fully power the mainspring? 156 turns of the rotor yields 1 full turn of the ratchet wheel…so roughly 1092 turns (7 x 156) should yield full power. When your 7S26 is fully powered down, you need to put about 1000 turns to get full power. When mine is fully powered down, I usually put 500 turns on it (actually not that difficult to count), then wear it… Or I put it on the winder and rotate it at 6rpm for 3 hours.
Following the above procedure should help point you in the right direction when diagnosing PR in the 7S26.
If power reserve is still a problem with watches that test okay…then most of the time they are not being powered up adequately to begin with…or the owner is too sedentary…or the watch is not being worn long enough.
, b t w the watch is a 7s26a-0020, skx007 made in nov. -96 according to the case back.
