Doxa 103

Doxa 103
Doxa 103

Description

The Doxa 103 is a high quality swiss handwinding movement of 11 1/2 lignes, which bases on the ETA 2391.

You can easily see, that the Doxa 103 bases on the ETA 2391, when you compare the inner workings. Their construction is identical, in both cases, the minute wheel is driven on the dial side via the third wheel. This wheel is driven by the fourth wheel with its thick axles and trains, which itself is driven by the mainspring barrel.

inner workings
inner workings

The center second is direcly driven. As you can see, the arrangement of the wheelworks is quite clever, using as few space, as possible. On the large 11 1/2 ligne main plate, there's a lot of solid, unsed space, which is a result of the fact, that the ETA 2391 is nothing but an ETA 2390, where the main plate is extended from 10 1/2 to 11 1/2 lignes, while the rest stayes the same.

main plate
main plate

The golden toned Glucydur screw balance is not yet shock protected, but carries a blue Nivarox-I hairspring, whose end is connected to a moveable stud. Altogether this was among the best things, which were available on the (mass-)marked at that time.

Nevertheless, there's a little downer: The Doxa 103 lacks any kind of find regulation, which means, that the effective length of the hairspring can be adjusted directly at the hairspring key only. This very cheap and crude mechanism does not fit into the picture of the otherwise high quality made regulation organ.

gold toned Glucydur screw balance with Nivarox-I hairspring
gold toned Glucydur screw balance with Nivarox-I hairspring

The Glucydur screw balance is a feast for the eyes!

dial side view
dial side view

On the dial side, there's ETA everywhere: The yoke winding system, the second wheel which its visible teeth at "7" and the massive axles, the third wheel, which indirectly drives the minute wheel at position "7:30" and last but not least the ETA-typical spreading spring on the hour wheel, which prevents it from slipping on shocks.

The partial minute dial on the lower part of the dial side plate indicates, that this movement is pretty old, since it was used in times, when timegraphers were not yet avilable everywhere, and helped the regulator to adjust the movement without mounted dial.



Technical data

ManufacturerDoxa
Caliber103
Number of jewels17
EscapementAnchor with pallets
BalanceGlucydur screw balance
Shock protection(s)none
Balance cock directionclockwise
Hairspring studmoveable
Regulator typeHairspring key
Movement constructionFork
Escapement wheel, Fourth wheel, Third wheel, Large driving wheel
Mainspring barrel
Construction typesolid construction
Bridge shapeTriangle, rounded shapes, 4 gears
Winding mechanismyoke
Setting lever spring4 holes
FeaturesSCD
FunctionsHour, minute, second
Beats per hour18000
Size111/2''' (measured: 25,6 mm)
Image in Flume Werksucher K2 -
Factsheet

Test Results

The movement came completely gummed into the lab, sealed in a watch wreck (see below) and hence got a full service.

Nevertheles, the movement has got a tiny problem: Since the gears are so near to each other and tend to "tumble" a bit, they tend to touch from time to time, slowing down the movement a tiny little bit.

It's likely possible, that this problem originates from the bad treatment, it got over the years.

Timegrapher Protocol

On the timegrapher, which printed here in double precision, the movement performed not bad, but still far beyond its possibilities.

While on the horizontal positions, the deviation is pretty low (at max. +15 seconds per day), three of the four vertical position show a bad performance, down to -45 seconds per day. It's quite possible, that this is due to the slightly "tumbling" gears. In the vertical positions, any gear will start tumbling, if no cap jewels are used. And if the gears are not 100% straight, you will see these problems. Unfortunately, the Doxa 103 lacks cap jewels, except one on the escapement wheel.

dial down
dial down

dial up
dial up

12 up
12 up

3 up
3 up

6 up
6 up

9 up
9 up

Usage gallery



Links
Ranfft Uhren: ETA 2391 (de) (en) (the base ebauche, ETA 2391)