C1) Is my LED repairable?
The chances are good, if some driver transistors failed or the oscillator circuit is damaged - unfortunately this doesn´t happens very often, and the module was destroyed by leaking batteries, that were forgotten in the watch, when it was less interesting at the beginning of the 80s.
If you think, the IC is still working, there is just one possibility: Sometimes big electronic companies offer a bonding service. That means, that they replace the little wires from the IC to the circuit board. If you own a watch with the Pulsar 201 or 301 module (Omega 1600 and 1601), the bonding is almost impossible, because the IC itself is placed under a ceramic body.
C2) repair service for your module..
Repairing costs 95,00 EUR plus shipping. The display of your watch shouldn´t show "18:88". A good assumption is a "1:" or any other kind of number, (f.e."0") or a strange letter (f.e."F") on just ONE of 4 digits. If you are not sure about the condition of your module, just send an email- help is for free.. If your module couldn´t have been repaired, this serive is also for free, except for the shipping costs. Service basically for the following modules: Pulsar: 10X, 20X, 30X, 40X, Omega: 160X. If it is hard to explain the mistake, feel free to send some photos.
C3) How does a LED watch work?
Processor and Clock:
The essential part of a LED watch is a small microprocessor, which controls the displays and all switches. The contents of such a microprocessor are usually the accumulator or "accu", a small ram/rom, a reset circuit to reset all functions as well as a few I/O ports, which control f.e. as IN-ports all switches of a LED watch in an infinite loop. An OUT- port function would be the controlling of the display unit f.e.. Early microprocessors weren´t able to generate their own clock, so this problem is solved with an external crystal, running at 32,786 Khz. This frequence is devided by either the software of the microprocessor or the microprocessor itself, so that the watch is running at 1Hz.
The matrix system:
All LED watches are working with a matrix to manage switch and display functions. Imagine, each segment of a digit of a LED display had to be controlled separately. If we take a closer look at the module below, we talk about 7 segments for each digit. A Pulsar watch with a 201 or 301 module is equipped with 3 complete digits (with 7 segments each) and the "1" digit with just 2 segments plus the 2 dots, which can be controlled separately, too. To run a watch with a separate controlling of each segment and the two dots, more than 25 I/O ports are needed, and we have forgotten all four switches yet. To avoid these costs and the much more complicated wireing, the matrix system was introduced. All equal segments of each digit are tied together. For example all upper right segments etc. You might say, because of the common trace between the equal segments of each digit, all segments light up, when the processor gives an "ON" signal for just one segment. This is right, but each digit has it´s own data line, the common anode or kathode, which depends on the display. If the display shows a "7" on digit 3, which means the two right and the upper segment light up, the CPU activates the line to digit 3 and to the common segments. All other digits stay dark, because just the common segments are activated, but not the digit. At 12:32, we don´t want to see just an "1" on digit 4 behind the red crystal, but also the 3 other digits... But the CPU switches after you have pushed the "time" button and starts from digit 4 then switches to 3 to 2 and finally to 1. The switching is so fast, that you cannot see a frequence on the display - it appears, that all 4 digits are lit, but just for the human eye. Very common are frequences around 50Hz which means 50 switches per second.
Other components :
On some modules you can find a small photo cell, which affects the brightness of the display. The brightness depends on the incidence of light through the red crystal of the watch. Small trimmers such as on the module on the lower left (marked potis), are responsible for the fine adjustment of the clock circuit. 7 drivers work as amplifier to to strengthen the signals comming from the OUT-ports of the micro, because the power of the outcomming signals is to weak to feed the segments. The switches on all 201/301 and 1600/01 modules are reed switches..
C4) Which batteries fit in my watch?
You can use some LR44 (quite cheap) or batteries type #357. OK, this type doesn´t fit in the hugh battery holes of the Pulsar/Hamilton or Omega modules, however the pression between backplate and module is high enough, that I had NEVER problems with batteries that shifted inside the hole, althought I wear my watch every day. Who thinks, this is not a proper solution can use the so called spacers. These are out of plastic tubes with the diameter of the #357 battery size. If you cut such a tube in small pieces, a battery LR 44 fits excellent in these modules. You can search for them on internet auctions, but think about the value of these things, before you press the "bid" button.
