The Watch Site banner

1 - 14 of 14 Posts

·
Registered
Joined
·
118 Posts
Discussion Starter #1
I've a problem with a oscillating weight, (Seiko 7s26) it's very sluggish, it's not spinning freely as it should, suspected a mainspring problem, took out the spring, cleaned and oiled it, put it back but same result, tried with an other barrel from a working 7s26 but same result ???? b t w the watch is is working if i use a screwdriver to wind it.

Any suggestions on a solution.

Regards.
 

·
Registered
Joined
·
845 Posts
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.

This is how I would further evaluate:

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.






Regards, BG
 

·
Researcher
Joined
·
5,027 Posts
Nice answer, and useful for others - but the OP seems to have forgotten his manners.
 

·
Registered
Joined
·
118 Posts
Discussion Starter #5
Wow, that what i call an answer, maybe a sticky, and it was not my intention to be rude or anything and i apologize for my manners for not reply, but sometimes you have other things in mind.

I have disassembled the whole movement and cleaned, reassembled and oiled it and it's a little bit better, and yes i managed to open the barrel, cleaned it, greased it with Moebius 8200 and the spring with D-5, i'm no watchmaker so i don't have all oils and greases as they use, don't know what breaking grease is.

There are no scuff marks on the movement and the pawl lever advance the ratchet wheel when i rotate the weight, even fully wind.

Thank you for a very nice answer and i will go thru the checking list.
 

·
Registered
Joined
·
118 Posts
Discussion Starter #6
First checkpoint, turned 10 times with a screwdriver and it took 6 turns (ccw) before the watch stopped, and now i have to wait and see how many hours the watch will run until it stops.
 

·
Registered
Joined
·
845 Posts
First checkpoint, turned 10 times with a screwdriver and it took 6 turns (ccw) before the watch stopped, and now i have to wait and see how many hours the watch will run until it stops.
If I'm reading this correctly, after letting down the power 6 full turns of the ratchet wheel...the balance stopped. Was there any tension left on the mainspring at this point?...If so, how much (1/2 turn, 1 turn, 1 1/2 turn, etc)?
 

·
Registered
Joined
·
845 Posts
... yes i managed to open the barrel, cleaned it, greased it with Moebius 8200 and the spring with D-5, i'm no watchmaker so i don't have all oils and greases as they use, don't know what breaking grease is.
Using 8200 on the barrel, will likely allow bridle to slip a bit prematurely. See this link on lubricants: http://hiro.alliancehorlogere.com/e...view_of_Modern_Lubricants_Used_in_Watchmaking

We use a moly based lubricant on the barrel wall...and either leave the alloy MS dry or use a very light touch of 8200 on the spring itself).
 

·
Registered
Joined
·
118 Posts
Discussion Starter #9
Checkpoint 2: The watch stopped after 41 hours and it kept the time well , and i think that's pretty okay for an older watch :), b t w the watch is a 7s26a-0020, skx007 made in nov. -96 according to the case back.

Approximately a 1/2 turn (maybe a little less) of tension left after the balance had stopped, and the same after 41 hour.

I've read the link (thanks) and i guess it's a little bit expensive for a hobby watchmaker to store all lubricants :(.
 

·
Registered
Joined
·
845 Posts
Checkpoint 2: The watch stopped after 41 hours and it kept the time well , and i think that's pretty okay for an older watch :), b t w the watch is a 7s26a-0020, skx007 made in nov. -96 according to the case back.

Approximately a 1/2 turn (maybe a little less) of tension left after the balance had stopped, and the same after 41 hour.

I've read the link (thanks) and i guess it's a little bit expensive for a hobby watchmaker to store all lubricants :(.
1/2 turn (or less) of remaining power is acceptable. PR 41 hour is acceptable. While I would use different lubricants, it appears that for the near term, your cleaning and selection of lubricants has lead to an acceptable result. If the autoweight is not impinging on the movement or caseback, if it is correctly lubed and if it will advance the rachet wheel when the mainspring is fully powered, and you are still experiencing an issue, then it is most likely is inadequate power to begin with, inadequate movement when wearing, or inadequate time of wearing (or some combination there of).

Good lubricants are expensive...what is your time worth? And what is the cost of having to repeat work which has failed due to selection of inferior lubricants. This is less important for the hobbyist...but any piece you give to someome else, you should be able to guarantee.
 

·
Registered
Joined
·
118 Posts
Discussion Starter #11
If you hold the movement like the picture and turn it around (see arrow) shouldn't the weight always stay in its lowest position even fully wound?

Thanks for the answers. but now it's bedtime here in Sweden :bedtime2:.
 

·
Registered
Joined
·
845 Posts
If you hold the movement like the picture and turn it around (see arrow) shouldn't the weight always stay in its lowest position even fully wound?

Thanks for the answers. but now it's bedtime here in Sweden :bedtime2:.
Weight will not always drop to "lowest" position with 1g acceleration. If ms is close to fully powered, there will be resistance and the "sluggish" operation you describe in the original post (at least on the 7S26). With motion to provide more than 1g acceleration, it should move, however. This varies among calibers and manufacturers. From the information you've posted, I fail to see a problem with your watch. As a final test, you should power the watch up (at least 3 turns of the ratchet wheel). Check the amplitude (one position only should be okay, provided the watch has been serviced and delta is within specs)...put it on a winder set for about 1000 turns per day (bi-directional)...wait 3-5 days and check amplitude and timing again. If this is okay and it is still running down, wearer needs to be more active or wear it more hours in the day.
 

·
Registered
Joined
·
118 Posts
Discussion Starter #14
The watch rather okay then, unfortunately i don't have a time graph to check the amplitude and other measurements, wish i had one, and my watch winder is a cheap one with just on and off, rotates 1 h and pauses 3 h, change direction is manually by a switch.

A huge thanks for your effort.

B t w here's a pic of the actual watch:
 

Attachments

1 - 14 of 14 Posts
Top