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Dec 24, 2012 11:31 am
Dec 24, 2012 11:31 am
Subject: Smiths Clock - How to reverse the polarity
Having decided to convert 108 to Negative Earth I thought I would reverse the polarity of the clock one of the few items affected by such a change. The procedure is fairly simple, if a little fiddly - here is the procedure I used;
1. In order to access the mechanism carefully bend back the tags which fix the chrome bezel to the main body, the front will come off revealing the hands and face be careful not to loose the spring and washer which are part of the hand adjuster.
2. Remove all four screws on the rear and lift the body off the mechanism be careful not to damage the hands when laying the mechanism down. Avoid touching the mechanical parts of the clock.
3. To reverse the polarity two things need to be done. First the diode needs to be removed and turned round in my clock it is a spring pressed against the disc diode which simply pushes into a slot. I removed the plate above the coil (and coil) to gain good access this also allows you to make the second alteration easily as well
4. Carefully remove the spring and disc diode watch out that the spring does not go flying off! Turn the diode around and reinsert with the spring in the same configuration as before I used thin pliers while someone else pushed the spring and diode in with a thin bladed screw driver.
5. The second alteration is to swap the connections over on the coil. I simply snipped the connections to the two pins, shortened the wires and re-soldered. It seems that this configuration works better so I wonder if it was intended that the clock be negative earth originally?
6. Its probably worth making a note of the change on the rear of the clock body with a fine indelible marker.
7. In my test, using a 12v supply, I had to manually move the pendulum to get it going again; I assume moving the car will do this when reinstalled.
Having decided to convert 108 to Negative Earth I thought I would reverse the polarity of the clock one of the few items affected by such a change. The procedure is fairly simple, if a little fiddly - here is the procedure I used;
1. In order to access the mechanism carefully bend back the tags which fix the chrome bezel to the main body, the front will come off revealing the hands and face be careful not to loose the spring and washer which are part of the hand adjuster.
2. Remove all four screws on the rear and lift the body off the mechanism be careful not to damage the hands when laying the mechanism down. Avoid touching the mechanical parts of the clock.
3. To reverse the polarity two things need to be done. First the diode needs to be removed and turned round in my clock it is a spring pressed against the disc diode which simply pushes into a slot. I removed the plate above the coil (and coil) to gain good access this also allows you to make the second alteration easily as well
4. Carefully remove the spring and disc diode watch out that the spring does not go flying off! Turn the diode around and reinsert with the spring in the same configuration as before I used thin pliers while someone else pushed the spring and diode in with a thin bladed screw driver.
5. The second alteration is to swap the connections over on the coil. I simply snipped the connections to the two pins, shortened the wires and re-soldered. It seems that this configuration works better so I wonder if it was intended that the clock be negative earth originally?
6. Its probably worth making a note of the change on the rear of the clock body with a fine indelible marker.
7. In my test, using a 12v supply, I had to manually move the pendulum to get it going again; I assume moving the car will do this when reinstalled.