[time-nuts] Odd FTS 4060 Behavior

[Adrian]

I have a FTS 4060 Caesium Frequency Standard that I never managed to get 
working properly.
When powered on, it locks properly after some 10 minutes and keeps 
running until it jumps off by about +1E-7. That is, the 10 MHz output 
then reads 10,000,001 Hz, and the red alarm light is on.
When I tried it yesterday again, it worked for about 2 hours before the 
shift appeared. Oddly enough, the green 'Locked' light was still on. 
This happens every 2...20 hours.

Any ideas what could cause that failure?

Adrian