The Bulova Thermatron is the first thermogenerated wristwatch in the World marketed in 1982 (P2 code) after years of research in developing this technology in wristwatch size. The whole concept is based on the thermo-electric discovery by Thomas Seebeck in 1821 which shows that a junction of two alloys kept in different temperatures produce an electric current. The thermogenerator consists of two metal plates (red & blue) that hold 4 groups of thermic couples in each corner. Couples made of antimon, bismut and tellurium produce 0.25 milliVolts when a temperature difference of 1.5 Centrigrade occurs. The 700 couples (175 in each group) produce a combined voltage of 175mV which by means of the electronic circuit and coil transform the insufficient voltage to the output 1.4V to run the 246 (245) movement.


The Thermatron achieves the temperature difference by means of the main body made of black fibreglass which perfectly insulates the steel caseback (which has contact with the skin of the wearer) from the top metal bezel (in room temperature). The blue and red plates are correspondingly connected with the top and bottom of the watch case and transfer the gathered voltage to the movement through a red and green wire. The Thermatron was far from becoming a success in the watch industry. Due to enormous costs and premature marketing of the watch it was a total disaster. If the watch was not worn the battery ended up completely discharged without a possibility to recharge it again by the wearer. Many of these watches were returned to the factory and caused severe financial problems for the Bulova company.


Base calibre 245 (Citizen 85) compared to Bulova 246

The entire stock was sold to a company called STW for rebranding and fitting a workaround. The solution required the capacitor to either be recharged by removing it from the watch or by kickstarting the movement so that it could once again begin producing thermo-electricity. STW modified the casebacks and fitted larger capacitors that could now be kickstarted (through a small hole in the caseback) with a smart device containing a 1.5V battery. A detailed analysis and repair hints have been presented by Richard Kunze from Germany (try BabelFish to translate). Check his ingenious idea to produce a caseback wrench for the untypical screwheads by using a hex screw. Hint: The original battery is no longer available so use a V6HR accucell (with spacer) in the unmodified Thermatron. Good, cheap, used in PDA devices.



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Keywords: bulova thermatron

Market value: 150-300$ (version, condition)


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