Wristwatch restoration, servicing and repair

Posts Tagged ‘Omega’

Omega ’53 (Omega Cal. 283)…

Another military watch on the blog, this time an Omega ’53.

(Click pictures to enlarge)

Omega were one of a number of watch manufacturers that produced timepieces for the British Military. According to official records, Omega supplied around 110,000 watches to the British Military during their partnership, the watch in this post being one of the models supplied to the RAF (Royal Air Force).

This model is best known as the “Omega ’53”, so named because it was only issued for one year – 1953,  making it one of the more collectible military watches. Turning the watch over, the now familiar military designation numbers are on the caseback, and the bottom line shows the serial number and year of issue.

You will also see these watches referred to as either a ’53 TA, or a ’53 FA, the two letters standing for “Thin Arrow” and “Fat Arrow” respectively. These watches were originally produced with radium filled figures and hands, and the Broad Arrow symbol was printed on the dial in a thin script, hence the name “Thin Arrow”.

In the early 1960’s the MoD started to withdraw from service all timepieces with radium hands and dial markers to replace the radium with non-radioactive tritium lume. As part of this process the dials were all stripped and repainted, and this time the Broad Arrow symbol was printed in a much heavier script, or “Fat Arrow”. (Comparing the two watches you will see that the subject of this post is obviously a ’53 FA.)

The watch arrived in running condition, but had seen better days as the dial was barely visible through the stained crystal. Opening the watch and removing the protective anti-magnetic/dust cover, revealed the movement, a manually wound Omega cal. 283.

A crystal that was too small had been fitted at some time in the past which had failed to make a watertight seal, and over the years water had seeped past the crystal and into the watch.

With the watch removed from the case, looking inside revealed the extent of the damage; the whole area around the crystal had rusted, and the dust/residue had worked its way onto the inside of the crystal – I can only conclude that the old steel tension ring had completely disintegrated here, as there was a lot of rust and very little damage to the case itself.

Aside from a little staining to the lume, the dial was largely unaffected, but when removed there was significant staining on the dial side of the movement. Thankfully, none of this was permanent and just needed careful cleaning.

Thankfully, the rust damage hadn’t penetrated any further, and the rest of the movement was in pretty good shape. It obviously hadn’t been serviced for quite some time, so after a routine service things were looking much better.

The remainder of the rust was removed from inside the case, the dial cleaned, and the correct sized tension ring crystal was fitted to complete the job.

Rich.

** Many thanks to Stephen Brown for letting me feature his watch on the blog. **


Omega Seamaster Memomatic…

I’m sure it’s obvious to regular visitors that I’ve got a keen interest in Seiko’s Bell-Matic watches. I’m looking to broaden my knowledge of vintage alarm watches and read about Omega’s Seamaster Memomatic model from the early 70’s, which shares a lot of similarities with Seiko’s Bell-Matic, so I thought I’d compare the two.

Here’s the Memomatic, it’s a great looking watch…

(Click to enlarge – pictures by a.r.a. gallery)

The first thing to point out is that rather than having a separate bezel for setting the alarm, the Memomatic has two discs in the centre of the dial which are rotated via the crown. This allows the wearer to set the alarm to the exact minute, rather than the ‘near enough’ approach used by the Bell-Matic and most other vintage alarm mechanisms.

The adverts from the time show that this was a major selling point for Omega, but looking closely at the service manual, a tolerance of +/-4 minutes is deemed acceptable when testing the alarm triggering mechanism, which makes it no more accurate than the Bell-Matic. Doesn’t this actually defeat the whole purpose of setting the alarm to the minute? Strange!

It has a very similar crown layout and operation to the Bell-Matic except that the alarm time can be set both clockwise and anticlockwise via the winding crown and date quickset is performed by pressing the recessed button between the crowns. The Memomatic mainspring can also be hand wound, the Bell-Matic cannot. (A scan of the full Memomatic user manual can be found here).

The engine in the Memomatic is Omega’s 980 calibre, which has 19 jewels and is slightly smaller in diameter than the Seiko at 30.8mm, (Seiko’s 4006A is 31.2mm) but slightly thicker at 7.8mm (the Seiko is 7.15mm).

It runs at 21,600bph (6 beats/sec) which is slightly faster than the Seiko which runs at 19,800bph (5.5beats/sec). Notice too that, like the Bell-Matic, the 980 has an independent sounding spring around the edge of the calibre rather than the hammer impacting part of the watch case as is common in other alarm mechanisms.

The biggest advantage that the Memomatic has over the Bell-Matic is that it has only one mainspring which powers both the going train and the alarm. As this is an automatic winding calibre, this also means that the alarm never has to be wound independently. If the watch is running, the alarm should be ready to go.

Reading the technical literature on the calibre, when triggered, the mainspring barrel completes one complete revolution which sounds the alarm for 8-10 seconds (about the same length of time as the Bell-Matic). How it manages to do this while still supplying power to the going train is very intriguing to me. Even looking at the exploded diagrams in the service manual it’s hard to work out how it does this.

I’d like to get hold of one and study it in depth but that could be tricky as only 35,000 examples were made and they now change hands for around the US$800 mark. Even when available on the high street, this technology still commanded a hefty price, the Memomatic originaly retailing at a higher price than Omega’s popular Seamaster Chronograph.

I’d better start saving up….

Rich.