This Seiko 4006-7011 came in recently for a service and to sort out a problem with the date changeover.
The Bellmatic line was originally released in 1966 and carried on to the late seventies. The earliest Bells used the date only calibre 4005a movement, these were soon phased out and the day/date 4006a was used from thereon in. The alarms spring is wound by the crown whilst the movement is wound automatically. To set the time of the alarm you pull the crown out one click and rotate the indicator on the chapter ring to the desired time. As soon as you pull the button above the crown out the alarm is then set, when it sounds just push the button back in to stop it.
The early Bells also had a higher jewel count, 27 as opposed to the later 17. You can see in the picture below that six of these jewels were used for the date ring to slide on! This seems to be over egging the pudding a little but these were fitted to overcome an issue which which translates from the Japanese as “the shake fall problem”. The only thing is I’m still not sure what the shake fall problem was!
The 4006a has an extra layer below the calendar mechanism that contains the alarm components, you can see the various levers and keyless work in the picture below. The little star shaped wheel acts on the hammer below it to actually sound the alarm.
On the motion work side of the movement you can see the sounding spring curving around the perimeter. Very early bells from 1966/67 had a longer spring that curved around even farther.
It was apparent why the date changeover wasn’t working. I found a little pin rattling around in the movement which belonged to the date changeover wheel, it must have become jammed at some point and sheared off. The hunt was on for a new one!
The movement was fully stripped ready for cleaning and inspection. Note the two mainsprings, the smaller one is for the alarm and doesn’t have a barrel, it coils up into a recess in the mainplate.
Whilst the movement was waiting for a new date changeover wheel to arrive I cracked on with the case. The owner wanted a new crystal fitting so the old one was removed. It’s not at all unusual to see this kind of crud in the nooks and crannies of vintage watches, in a way it’s quite reassuring as it’s evidence that points to the probability that no one has has messed with it before you.
The missing part arrived and the movement was finished off, this was just after the alarm indicator ring had been fitted.
The dial and hands on this example are in remarkable condition with no damage, fading or staining apparent anywhere.
The movement has been recased in this picture, all ready to renew the caseback seal and close it up.
And here she is finished and looking splendid. These Bellmatics are fun little watches and are still quite affordable at the moment. This one in particular has a very desirable dial design and case style.