[time-nuts] FE5680A signal output

[Remco den Besten]

I recently obtained a FEI FE-5680A Rb standard Revision: B.

After powering it up 'out of the box', a lock @ 50.25505.. MHz was obtained
within
a few minutes, confirmed by measuring the lock indicator on pin 3 of J1 and
listening to the signal on my FT 857 receiver. Nice to hear it sweeping
before locking ;-)
Here te levels at pin3 of J1 are: unlocked +4V, locked +1.5V

A 1PPS signal could not be detected with a multimeter, so I connected a
scope.

I consider the signal levels somewhat peculiar and am curious if FE 5680A
owners
here have the same experience. E.g. the amplitude of the PPS signal at pin6
is superimposed on a DC offset of ca. 170 mV and amounts (only?) 25 mV.
It is visible as a small spike here (depending upon the time base of 
course).
My perception of a '1PPS' signal is a signal with TTL levels or open
collector out or something, and a pulse width of 10 - 200 ms..
I connected a 2k2 resistor between pin6 and pin1 (pull up) but could not see
any improvement. The top-top amplitude remained ca. 25 mV.

Pin6 (measured with scope) spikes with t = 1 sec:

200mV       |      |      |
170mV ------|------|------|

The signal above will be hard to interface, but I feel that perhaps the PPS
output is not 'set' or perhaps broken.

After powering up, the unit draws 1.6A which gradually decreases to 800mA.
This looks normal.

Anyone any ideas?