Mail Call 235, not 236! I got the title card wrong. November 22, 2024

@greenerick
Could you please share your thoughts on the Seiko Spring Drive movements?

@truebluemiata
Question about the 7ax8 svs manual. It showed an adjustment trimmer. I recall you saying that the only shortcoming of these is that it lacked a trimmer, having only several wires to clip to adjust accuracy. Am I misremembering?

@BlairWitchProject
Another Resist/Proof from early 1970! I will add this to my database. None of the resist/proofs I’ve seen have dial dates

@BiffTannenBTTF
I think Daniel Blair has a list of serials for several proof/resist 6105’s. I also owned one that was about 150 units away from Daniel’s watch. So I do believe it was a thing based on his evidence that they were from a short period of time in summer 1971. [Regarding the Seiko mainspring question] - I would think that there must be a mainspring out there for Swiss watches that comes close to the dimensions of the 6159 spring

@bobbressi5414
My major experience with Seiko movements is that every watch that I own with a 7s26 movement keeps better time than my watches with newer NH35 and 36 movements. I'm not really sure why that is.

@philipmccracken697
Of course the amplitude is lower by design. Do you think Seiko doesn't know how to engineer a watch movement?

@vectorgen
Do you think that Seiko deliberately underpowered these movements specifically because the arbors were not jeweled? You should put a beefier mainspring in a non-modified movement and see if it causes damage.

@WeekendWatchRepair
Hey Spencer, I’ve been wondering the same thing. Perhaps would the 6146 spring be the same as a 6159? I haven’t bothered to look it up, but the dimensions on the 6146 should fit fine in the 6105 barrel, although it is slightly shorter and will affect the power reserve. Not really an issue though in an automatic movement. Overall, it has the same dimensions except for thickness, which is 0.15 in the 6146 instead of the 0.115 on the factory 6105 spring. GR2537X shows to be the part number from cousins, however I don’t know if the inner loop on the spring will accommodate the arbor without adjustment. I will source one of these springs and give it a try on a freshly serviced movement. (edited)

@brucebarlow6604
Yeah I think you are correct. My 6309’s and 6105’ are putting out 210-230 amplitude, my 6138 however puts out 260-270 with its original mainspring. When I do use an aftermarket new spring I’ve had good results with a GR25341x they take a little longer to come up to full power but when they do they hold good amplitude. Also to consider is what grease and oils are being used in the barrel and on the pallet stones. I get good results using 8213 on the barrel walls, 8200 on the spring and 9415 on the pallets jewels, I never use Seiko grease. A great topic to see what results others are finding.

@Nghdsjd
That makes sense, and the only problem, the reduced power reserve from the reduced length, isn't really that terrible on an automatic watch anyway. Coincidentally, I have a Citizen 8110 chronograph movement that had a broken mainspring and tried to find a good replacement, and noticed that the Seiko 6106 etc. spring is a actually good fit. It's just a bit longer and thinner. Turns out that results in a bit too poor amplitude and poor timekeeping for the 8110 (which of course is a higher beat movement). If you find a stronger spring for 61 series, that should fit the 8110 too.

@VintageWatchServices
It's a great question and a very interesting discussion but I think the premise is wrong :) 270 is just a convenient number (3/4 of a full rotation), set by the Swiss based on their ways of doing things.

@markos1388
Is this also underpower problem with my Seiko 5 6119-6003, is 6159 barrel compatible ?

@Supercruze
Nice observation. I typically see anywhere from 210 - 230s on a serviced 6105, 240s on a good day. I have always thought a hotter spring would solve this issue. Thanks for your vid. I guess the tradeoff would be slightly lower power reserve.maybe.

@cmb1972
HI, a channel on YT " weekend watch repair" who mentions you regularly BTW, has substituted 6138 mainsprings with swiss mainsprings with higher amplitude results. Might be worth having a chat with Adam.

@JxH
QUESTION: In an Automatic movement, would it still be capable of self-winding given a stronger-than-stock mainspring ? Perhaps they settled on a more delicate (wimpy) mainspring so that the Automatic system (where applicable) has a chance to push it around. Maybe the counterweight would need to be switched to a more aggressive one, but then the case might not fit.