As has been mentioned by Pete and others the majority of the inexpensive 5680 units can only be adjusted for frequency by inputting rs232 info. I am experimenting with a simple mod to add a fx adjust pot to my unit. I removed the unconnected "dummy" pot and glued a miniature 100 k pot upside down in the area where the original pot was. Its connections are on the top of the pot. Cold side of pot went to ground, hot side of pot went to output of 8 volt regulator through 1 k resistor. Wiper goes through a 100k resistor to pin 5 of the chip next to the ribbon connector. (To find pin 5 have unit positioned with db9 connector at upper left, ic area will be in lower right. Pins 1 through 7 are between the chip and the ribbon connector - pin 1 is at the extreme right next to the marking on the chip - count left to pin 5! I got my 8 volts from the 8 volt regulator that is the first xsistor of the two that are mounted on the vertical heatsink. The third pin is 8 volts output. Pins are counting down from db 9 connector area.
Three hours after doing this mod my unit is about 5x10-12 high. The voltage on pin 5 is 3.52 volts. I have my thunderbolt 10 mhz output triggering my 465, the 10mhz from 5680 going to vertical input, time base set to .1 usec and the x10 mult on giving me .01 usec per div. With a stopwatch I time the time it takes for the trace to move one division. I divide the seconds measured and divide that into 1 to the minus 8th and get the offset. in this case 1 to the minus 8th divided by 195 seconds gives me about 5 parts in 10 to the 11th. The trace is moving to the left which means the osc is high. I would appreciate any of the 5680 gurus to go over my math and what I have done and let me know if I am all wet!! Thanks to all of the threads on this unit that have been on this list. 73, Bill Riches, Wa2dvu Cape May, NJ -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of saidj...@aol.com Sent: Thursday, December 22, 2011 1:39 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Using Thunderbolt to Discipline FE 5680A? Hi there, maybe this has already been discussed here.. There is a small hole on the side of the unit with a small trim-pot visible through the hole. Does anyone know if this is an analog frequency adjustment? If it is, maybe that trimpot connection can be used as disciplining input.. Thanks, Said In a message dated 12/22/2011 09:20:57 Pacific Standard Time, albertson.ch...@gmail.com writes: I think the FE-5680A has to course of adjustment to be used in the "fast" control loop inside the t-bolt Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
