Author Topic: Service: Bulova Accutron cal. 2181  (Read 4191 times)


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Service: Bulova Accutron cal. 2181
« on: May 17, 2015, 05:13:11 PM »
I have previously met 218d and this is mostly similar. Small differences are in the calendar mechanism. Mostly, to my understanding, to ease the reassembly.
This watch comes to service with box and papers. Rare set these days.

Watch has clearly collected dirt inside, but the watch was still in operation when it arrived. First I take off the casing spring, which tensions against case back to support the movement. Below this opens the view to see the tiny fingers which turn the index wheel.

Jewels are dry and there's enough dirt.

Fingers are dirty too. It's indeed time for a service.

The principle of the calendar is quite simple but functions well. In the latter picture the small wheel turn the "arrow tip" (date trip wheel) which builds tension to the spring during the day. This tension releases at midnight and releases date indicator trip arm to advance the date wheel. This makes the date change instantaneous.

Tuning fork removed from the movement. The pawl finger is not removed from the tuning fork during service and this makes handling the tuning fork very critical. If tuning fork flips, Mr. Murphy pays you a visit and you can expect to see at least distorted finger.

Little bit off focus, but here's the index finger held in the plate, which is adjustable. When hacking function operates, index finger is lifted off of the index wheel to stop it to rotate. Pin sticking out of the hack lever assembly bends the finger little bit which is enough to stop index wheel rotation. This bend should be ½ width of the index finger tip (the part). This is important, because if bend is too much, it can change the static position of the index finger.

Fully dissassembled.

The crown gasket has completely dissolved and that's because of bad quality silicone grease.

Non-critical part cleaned in normal watch cleaning cycle. The delicate parts get special treatment.

Fingers and index wheel are so delicate that these cannot be put in the cleaning basket, as they would damage in the cleaning process. In the ultrasonic I have normal water based cleaning solution in the bottom but in the cups there is normal cleaning solutions: cleaning and rinse.

Ultrasonic in operation.

Because Accutron can operate long without been serviced, many times the cannon pinion greases solify, causing cannon pinion to jam. If this happens and time is set, wheels can get broken. Here I put the cannon pinion upside down first to lubricate the friction surface.

Here correctly assembled.

Keyless assembly.

The calendar quick set claw missing still.

Hack lever goes to the bottom. In lower section of the hack lever is the pin which bends the index finger in hacking mode.

Firstly the index finger back on. One (the most below) of the screws is off center one to allow adjustment.

Tuning fork assembled.

At this point extra carefulness required. If finger stays in wrong position, no alarm is given while bending happens.

Before the wheels oils to the jewels.

This time this part went too easily as the train bridge just dropped in its correct place.

Fresh battery and the hum begins.

Few extra closeups.

Pawl finger vibrating. Here I'm adjusting the hacking. This is too far from the index wheel.

I tried to take picture of the date quick set claw. It's pointing up, here.

assembling the date mechanism is quite delicate. Two simultaneous springs are tensioned here and the date trip sprig is quite forceful.

Waiting for the dial.

There is lot of discussion whether to put old style 1.35 V or 1.5V battery into these. Originally Bulova have spec'd these watches to survive even 1.7V, so nothing will fry with 1.5V battery. If the watch is adjusted to 1.35V battery and 1.5V battery is replaced, the watch will start to gallop, run fast. This is because higher voltage causes bigger amplitude to the tuning fork. Bigger movement in tuning fork causes pawl finger to swing more and this causes index wheel to advance 2 or more even more teeth per one vibration.
The amplitude of tuning fork can be adjusted and this is simply done by adjusting the force the fingers push to the index wheel. Here it sounds easy, but in real life it's little bit delicate process.
This watch run first at too high speed, but after adjustment it started to run just fine.
I recommend to use normal 1.5V battery. Reasoning: these are the most fresh, modern batteries with best operation life. There are also batteries and battery adapters, which are based on diodes, but when these are used, they only can use the volume the original battery has. This means ultimately poor operation life compared to battery of "full volume".

New tension ringed crystal and new gaskets and this one is ready to head home.