UMF 28-40
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| UMF 28-40 |
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Description
The UMF Ruhla caliber 28-40 is a true quarz movement with stepper motor, and hence not a target
of this collection, but its unusual construction saved it a place here:
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| movement without electronics board |
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As you easily see, the 1978 launched caliber 28 bases on most parts of the several
million times produces
Kaliber 24. The modification
for quarz driving was relatively moderate: At the place of the mainspring barrel, a large Battery of
type LR 44 was set as powering source, and instead of the escapement works with escapement and
balance, a rather large stepper motor was used. The rest of the movement remained more or less
the same, even the center second hand was indirectly driven, just like on caliber 24. This
constrution is pretty unusual and rare for a quarz movement.
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| Overlay of caliber 24 and 28 |
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Electronics was already quite advanced at the end of the seventies, so this movement only
uses a tiny quarz, an integrated circuit and a trimmer condensator for regulating the quarz. This
construction was so timeless, that even today, modern quarz movement are built the same way, except,
that on most modern movement, the costly trimmer condensator is already lacking.
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| electronics board |
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The electronics board was pretty large and therefor had to be placed besides the actual
movement. The new plastic board, which was then required blows up the size of the new movement
to giant 14 1/2 lignes, which are almost 33mm. By now it's clear, why this movement had to be
replaced soon by a true (small), newly developed quarz movement.
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| electronics board, downside |
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However,t he usage of an integrated circuit shows a general Problem: When, e.g. by drowning
water, the circuit goes out of order, especially after many years, it's no longer possible to
repair the movement, since no replacement parts (replacment ICs) are available.
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| dial side view |
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On the dial side, you see the familiar construction, known from the UMF 24-33, with its
very simple date mechanism in plastics, the date disc spring and the rocking bar winding mechnism.
On that mechanism, the now useless top gear is removed.
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| dial side view without date disc |
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Technical data
| Manufacturer | UMF |
| Caliber | 28-40 |
| Number of jewels | 0 |
| Escapement | q |
| Movement construction | Escapement wheel, Fourth wheel, Third wheel, Center wheel |
| Features | SCI,QG |
| Functions | Hour, minute, second, day, quartz controlled |
| Beats per hour | 3600 |
| Size | 141/2''' |
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| Factsheet |
Usage gallery
