The Pre-Minivox: The pre-production model of the Jughans J89

A myth gets a face - Junghans J89 Minivox preproduction


Junghans J89 Minivox Vorserie; Front; foto: Fischer; collection: Fa. Junghans/Schramberg


Junghans J89 Minivox Vorserie; Front; foto: Fischer; collection: Fa. Junghans/Schramberg

There were several significant patent disputes and competitions in history to bring inventions to the market: Samsung against Apple, Google against Microsoft, Graham Bell to Elisha Gray and Thomas Edison against Emil Berliner.

Also Junghans can provide a tangible patent dispute - against the in the Swiss La Chaux-de-Fonds based firm Vulcain (Fabrique de Montres Vulcain).

The patent dispute was about the diaphragm back of the watch which should amplify the sound of the alarm clock by more ressonanz. Junghans lost the patent dispute in 1947 about the launched model " Cricket " against Vulcain.

The case of The Junghans J89 designed by the brilliant designer Albert Letsche had in its original version but more to offer than Vulcains "Cricket" because the loudness could be adjusted by means of a small lever on the diaphragm base.

The diaphragm base

- with lever and sound holes (pre-series) and without (standard series)


Junghans J89 Minivox preseries; back; foto: Fischer; collection: Junghans/Schramberg


Junghans J89; Junghans 689.70; Minivox; back; standardseries

Letsche who came back injured from the war, immediately began with the construction of the Junghans J89 and the legendary Junghans chronograph J88. The construction of the J89 was probably finished already after half a year, reaching (according to Letsche) already 1946-47 to  series production.

The original design of the case of the J89 still had a double diaphragm base (patent and patent), which promised a loud alarm sound and was equipped with a small lever to adjust the volume. Unfortunately, Vulcain has patented this double bottom before Junghans. Letsche was therefore forced to optimize the sound volume and otherwise solved this by a perfect attaching of the diaphragm base in the case and a perfect positioning of the anchoring of the lever, where the hammer hits. The best position is the center of the diaphragm base. Also Albert Letsche has been tested the material that had the best and loudest properties. From the patent: "The sound volume and purity can be further increased if the following measures are taken, which already individually on their own, but in particular in cooperation will bring success: The alarm hammer should at least insist on his serve part of hardened steel; preferably is riveted to an unhardened hammer body a hardened striking piece. As has been shown in extensive trials, the maximum loudness at a number of beats of the hammer 25-37 per second, reaching an average preferably from 31 beats".

In order to have available the greatest possible main-spring for the movement which provides by a more constant power output significant advantages over smaller barrels, he built only a single barrel, instead of using as many competitors two mainsprings - running and alarm. This always makes available the full and uniform torque of the mainspring for a better regulation. There is more space for the actual movement available by accommodating only one barrel.

Despite the use of only one spring, the duration of the ringing is up to 10 sec and after the use of the alarm there is at least 30 hours power reserve available.

As seen from the Patent the engineers wanted to show a similarity to a chronograph with the watch-design.


Junghans J89 Minivox preseries; back; foto: Fischer; collection: Junghans/Schramberg


Junghans J89 Minivox preseries; front; foto: Fischer; collection: Junghans/Schramberg


Junghans J89 Minivox; preseries; crowns; foto: Fischer; collection: Junghans/Schramberg


Junghans J89 Minivox; preseries; back; foto: Fischer; collection: Junghans/Schramberg

The Junghans J89 is very easy to use:

The crown at 3 is the same handling that you expect from a "normal" watch. Winding the mainspring and in first position setting the time (in both directions).

The crown at 2 for setting the alarm hand. This extends through its length in the early Minivox-dial designs in the outer scale and can easily be read in 10 minutes increments.

The smaller, non-knurled knob at 4 o'clock is for starting and stopping the alarm and can hardly be stopped accidentally, because it allows only in the depressed position the alarm event. However, the pressing need for a certain resistance.

A word of advice for hobbyists: When pressing the back cover, ensure that the crown case is perpendicular to the top and the notch coincides in the lid with the nose on the case. Only in this way ensures that the hammer is in the correct position and is not damaged when the lid will be closed.

There are different versions available of the caliber J89:

The caliber J89-2 with only 17 jewels (for the US market; fewer jewels because of the otherwise higher duty import charges), eg for Bulova

The caliber 89-3 with raised hand tubes for curved dials

The later versions also have small changes: the number of jewels used by then has increased from 20 to 21 because the friction spring on the second hand received an additional jewel to reduce friction. There later on was also a small spring, which presses a gear on the alarm pointing wheel, installed to prevent that the teeth could not engage at the onset of resinification of the lubricant.

For more information: Junghans J89; Junghans 689.70

Use of photos: Courtesy of the Junghans company / Schramberg; with kind permission: Junghans / Schramberg