Seiko 7A38 - by the numbers

I bought a non-working 7A48-7000 from ebay recently, if nothing else for the bracelet and spare parts.

It had a very leaky battery inside, along with significant sign of rust - either from the battery itself or possible watrer ingress from the 10pm pusher. You can see the staining on the case back:

But the case itself, front and back were in good condition:

if rather dirty!!

The dial was stained from the rust, but cleaned up very well:

So, I thought this was an ideal opportunity to take a look under the dial and see how the moon phase complication works.

Dial off:

to reveal:

See the tension finger spring at about 3:30pm on the moon phase disk.  Zooming in to the complication itself:

with the crown at the 1st click position, turning the crown in one direction (away from oneself), the 'finger' moves up and down in a vertical plane with each revolution advancing the small gear to the left of the moon phase disk, which in turn advances the moon phase disk.

Here you can see this vertical movement:

Turning the crown in the opposite direction (towards oneself), the finger moves across (and under the moon phase disk):

Removing the moon phase disk:

we can see underneath:

a second gear wheel, which is the date wheel (so I guess has 31 teeth?). We can see the end of the 'finger' engaging with this wheel - this is the quickset for the date.

We can also see how the day of month changes in normal operation - see the tiny notched tooth on the gear wheel with the square teeth. See also the tension finger spring.

I didn't remove the plate which holds the complication gearing. That's for another day 

Here is the reverse side of the movement, after it had had a substantial clean-up:

It all looks very familiar. But unfortunately despite all this good work the watch was dead.

This is what was hiding underneath:

and in closeup:

which despite it looking OK from this side:

was a dead circuit 

But ......... it was worth swapping in a working circuit.

and

amazing - but it still works!!

this circuit came out of a battery damaged  7A38-7270.

Super photos and write-up, as always, Simon ! 

I think you may have confirmed something I wrote in the 'Are 7A28 and 7A38 modules interchangeable?' thread:

By the way, the culprit responsible for that 1.0mm difference in thickess, between 7A28 and 7A38 movements, is probably the least aesthetically pleasing component used anywhere in any 7Axx - the day / date spacer ring / dial mounting plate p/n 0105726*.

*The 7A48A movement uses p/n 0105725.

I presume it is the same 1.0mm overall thickness as p/n 0105726, with different internal cut-outs to clear the moon-phase complication.

I don't suppose you thought to measure the thickness of the 7A48's spacer ring, while it was still dis-assembled, by any chance ?