My father received this Accutron as a wedding gift from his parents about forty-five years ago. He wore it religiously but at some point in the 1990’s switched to wearing more robust tool watches. The funny thing is that none of those tool watches have held up as well as the Accutron has over the years.
A few months ago he gifted me the Accutron on account of my keen interest in horology. The watch no longer ran but being an electrically driven mechanical movement I figured on the battery having been long dead. A replacement battery confirmed my suspicion but soon after patting myself on the back for a job well done I noticed the minute and hour hands seemed to be stuck in place.
A bit of research on the web brought to my attention a well known problem with Accutrons- the center wheel assembly is susceptible to oxidation (rust) which will cause it to seize; the symptom of such a seizure is movement of only the sweep second hand. Clearly a service was called for.
The Accutron movement is completely different from a typical mechanical watch. While a mechanical watch is powered by a mainspring, the Accutron is powered by a battery. A mechanical watch’s timekeeping ability is regulated via the escapement (balance wheel, pallet fork, and escape wheel) while an Accutron’s timekeeping ability is derived from a vibrating tuning fork, a jeweled finger and pawl, and index wheel which converts the lateral motion of the fork into the rotary motion needed to drive the gear train. The finger, pawl, and index wheel in an Accutron are amazingly small. It is due to the delicate nature of the Accutron movement that I didn’t even attempt this repair until several months after my father gave me the watch.
Disassembly began by removing the threaded retaining ring from the case back. With the retaining ring removed, the case back came away from the case revealing the movement inside.
The battery cell is held in place with a ground strap and two retaining screws. Loosening the screws, I lifted the battery out and revealed a bit of corrosion from a previously failed cell.
Next the movement was removed from the case.
The dial is held in place by two small screws on the side of the movement. I loosened these to lift away the dial. The work of a previous watchmaker was apparent as one screw was an ill fit and must have been a replacement.
Having never serviced an Accutron watch before I was keen to do my research before getting in too deep. Fortunately I was able to find the service manual for the movement online. It was a good read and prepared me for some of the surprises a first timer might encounter. For example, I discovered that Bulova only uses two types of lubricant on this movement. The Molykote grease used in the date mechanism has mostly dried up since the last service.
This was only the second watch I’ve worked on with a date mechanism and the Accutron has a wonderfully snappy date feature. I was very careful to note the location of each spring required to make it go.
The center wheel assembly put up a bit of a fight which was expected. I don’t have a proper cannon pinion remover- my tool is a cannon pinion/hand puller device which comes up short sometimes. In this case I used a small pin vice to remove the assembly as it could grab all the way around the pinion head with equal pressure.
Next I flipped the movement over and began breaking down the topside. First off was the large jeweled bridge that secured the gear train in place.
With the bridge off, the gear train came away simply which left the tuning fork, coils, and hack mechanism.
The most difficult part of the disassembly was ensuring that the tiny jeweled finger that moves the index wheel was not damaged- and also to keep loose screws from contacting the highly magnetized coils!
Once the movement was broken down most of the pieces went off to the L&R cleaning machine. The index wheel was cleaned in an ultrasonic bath as per the service instructions, and any electrical parts were carefully cleaned with bit of rodico.
The case was dirty and the crystal badly scratched so it was removed and then the case was run through the ultrasonic cleaner.
Reassembly began on the dial side with the center wheel assembly and setting mechanism.
The hacking mechanism was then assembled on the top side before installing the tuning fork and coils. As with the bottom plate, Molykote grease was used exclusively to keep everything moving properly
The tuning fork was assembled with the coils under the microscope before being secured to the plate. In the picture below you can see the jeweled finger which contact the index wheel with each vibration of the fork- it’s quite small and exceedingly delicate.
Next came the gear train followed by the jeweled bridge. All of the pivot jewels on the Accutron movement are capped which makes cleaning and oiling them a bit difficult. I invested in a high quality injection oiler just to make sure this job was done right.
With the base movement reassembled it was time to get onto the date mechanism. Reassembly was the reverse of disassembly but it still proved difficult as there were two springs to set. Sadly for me, I didn’t realize the date mechanism was covered in the back of the service manual (let that be a lesson to all to read cover-to-cover) and as a result I thought the date trip spring had to be placed under tension before the date bridge was screwed down; the spring shot away from the movement (repeatedly) until it was lost.
Once the replacement spring arrived I was back in business and it didn’t take long to finish the job. Reassembled the watch came to life with a new battery although it did run a bit fast. Adjustment was a tedious process to set it just right but I am very happy with the end result. The watch has been cleaned and renewed and is ready for another forty years (with periodic service of course).
When Bulova released the Accutron watch it was with great fanfare as more than a decade of development had gone into the electro-mechanical movement. The Accutron was the most accurate watch in the world and a true wonder of engineering. Unfortunately, within just a few years of it’s release, it was superseded in accuracy by Seiko’s quartz movement. With Quartz watches trumping mechanical watches (including the Accutron) in price and accuracy, mechanical watches soon went out of vogue. Bulova ceased production of the Accutron movement in 1977.