Continuing on with the saga of my Seiko watches, when we last left off I had replaced the batteries in both watches in the hope that this refresh would keep them from running down so frequently. The newer watch has, subsequently, returned to an acceptable level of functioning, but the old one still tends to run down to zero after a few months.
Of course this isn't entirely surprising, since I only wear the older one once a week, however I tried to address this, years ago, by storing it in an automatic watch winder when it isn't on my wrist.
Rather disappointingly, this did not solve the problem, and the reason why is pretty straightforward: the device is programmed to only rotate the watch for something like 15 seconds every hour. This rotational austerity is done in the name of not over-winding a mechanical automatic watch, since as we all know, overwinding a mechanical watch can cause the mainspring to be damaged or broken.
Except that watchmakers aren't idiots. A regular non-automatic wristwatch has a mainspring that's retained in the barrel by a hook and on the arbor by another hook, creating a positive connection to the spring at both ends, which is sufficiently strong that overpowering it will result in breaking the mainspring.
HOWEVER, automatic watches only have a hook on the arbor, and the barrel is instead smooth, with the mainspring gripping it via friction through a specially formulated sticky grease. If the watch is "overwound" then the winding action pulls the mainspring away from the inside of the barrel and this reduced pressure allows the spring to slip along, safely releasing the excess spring tension.
Never mind that my Seiko watches don't even have a mainspring. The automatic works runs a little generator that charges the battery.
But it's easier to sell people snake oil to alleviate their unfounded anxieties than it is to educate them and dispel their misunderstandings, so the result is we get an automatic watch winder that doesn't actually properly wind an automatic watch.
Now I've known this for a while and I've been mulling over ways to address it. I could replace the control board with one that's programmed more to my liking, or possibly just reprogram the control board that's already in there, but both of those options feel a bit tedious and excessive. Instead, I'm just going to install a switch to bypass the whole thing so that I can set the motor on to run constantly when I need to fully charge the watch.
And that starts with getting inside.
The winder can be optionally powered by a pair of batteries, but I run it off the wall-wart. Still, the battery compartment is one of the two main access routes to get inside the unit.
And the control board is just held in place by the nuts on the knobs and barrel jack.
The watch holder basket thing is held onto the gear motor shaft by a single screw, and another single screw holds the diagonal main plate in place. With those removed, everything comes apart.
There's not a ton of room in the bottom of the case, but I should be able to fit the switch here beside the basket where it'll be easily accessible from above.
Though the main plate is a little thick compared to the barrel size of this switch, so I'll need to carve out some space on the back side.
First up is drilling the hole.
Which worked pretty well, despite going through a layer of fabric on top.
And it's clear to see that we won't be able to get the retaining nut onto the switch without a bit more work on the backside.
But a little work with a 3/4 spade bit (which I had to run in my cordless drill because it's a cheap bit and not anywhere near straight) makes a nice little pocket for it to sit down inside.
And now we've got enough threads showing to secure the switch in place.
The nut and the anti-rotation washer go on just as planned.
And now it's time to solder. These two contacts on the programming header connect to the ground plane and the power input jack, so they make a convenient spot to tap into.
And then the switch gets soldered up to select between either the normal PCB connection or the direct power connection.
Then all that's left to do is pack everything back in the case like it was before.
So now whenever my watch is getting low on charge, I can just flip the switch to have the motor run constantly (and faster than normal too, since the new connection bypasses the 3.3v regulator) and leave it for an hour or two to make absolutely sure that the battery gets completely topped off.