Some of these watches run fast which must indicate an indexing problem. In the meantime I have set the adjusters to midpoint on all my 14 problem watches and started a 24 hour test so I can get a good baseline. I have got a stroboscope coming but time will tell whether it is any use. It would be very helpful and speed up things if I had a Vibrograph or something else to directly measure tuning fork frequency. No watches go to the display part of my collection till they do! I don't give up and will eventually get them all keeping time to within factory specs. I intend to try replacing the component coil in this watch. I suspect that by slowing the circuit timebase the fork frequency may be being dragged down. One of the slow runners, which incidentally has a NOS movement, has a capacitor which reads 0.4 microfarads. The solution can then only be to replace the index wheel. If one tooth is skipped per rotation the watch will gain 4 minutes per day which is in line with what I see. Love to get some feedback on this, particularly from the experience of others servicing Accutrons. I hope to be able to produce a graph of weight removed against frequency change. Fortunately I have an analytical balance so can do this with great precision. I intend to do some experiments by filing a known amount from the upper outer edge of the cups and then redetermining the the rate of a watch. I can only conclude that over time there has been a drift in the metallurgical properties of the forks themselves which has lowered their resonant frequencies.When the forks were manufactured it looks like they had a higher frequency and were adjusted downwards by filing a semicircular notch at the base of each tine, thereby reducing the stiffness of the tines. If this were the case a run current greater than 10 microamps would be observed. This is not caused by any obstruction to the tuning forks, gear trains or hands. I have found that about 1 in 4 of the Accutrons I have serviced run slow at a rate outside the range of the regulation adjusters.
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