[time-nuts] FE-5680A pin 6?

EB4APL eb4apl at gmail.com
Fri Sep 11 16:16:05 UTC 2015


Hi Nick,

FE-5680A is a whole family of Rb oscillators that have in common the 
case and name but the functionality, connectors and inner stuff varies a 
lot.  Some are programmable on a wide frequency margin, others has a 
fixed frequency output, mostly 10 MHz.  The connector arrangement also 
varies but you probably are referring to one with the P/N 217400-30352-1.
These units have a 1 PPS output on pin 6, the signal is normally at 0 
volts with a 1 uS wide 1PPS at about 5 volts.  This low duty cycle 
signal is difficult to see on an analog scope but you can see the 
trigger light blinking at each pulse.
The 1PPS signal is buffered by U503, a 74ACT240SC-ND chip. A word of 
caution here: since the driver circuitry is shared with the Lock output, 
an excessive (ie. a LED) load on the lock pin cause the 1PPS to 
disappear.  Please recheck the output voltage on pin 6, -5 volts doesn't 
make any sense for me, even with a driver chip failure (I have busted 
mine some time ago by connecting the +15 V power supply to the 5 volts 
input, a consequence of the disperse information about these units that 
circulate on Internet. Apparently on some units pin 6 is the +5 volt 
input so you can also ruin the driver following this wiring list.
If you are interested I have the board schematics that was reverse 
engineered by a member of this list who unfortunately I cannot give 
credit because I don't remember who is.  I can send it it directly to 
you if you want it.

Regards,
Ignacio EB4APL


El 11/09/2015 a las 3:06, Nick Sayer via time-nuts wrote:
> I’ve acquired an eBay 5680. I’ve hooked it up to +15 and +5 and am getting 10 MHz out and the test pin is low. The unit is warm and within any reasonable expectations, it appears to be working properly.
>
> What I wonder about is pin 6 on the connector. Google results seem to indicate that that’s supposed to be a PPS output, but what I get on it is a fixed -5v or so. Anybody know what this signal is supposed to be?
>
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