Hi Ed Can't help with the oscillator but the 74xx140 is a dual 4 IP Nand 50 ohm line driver, you'll probably find more data available if you search on 74S140 rather than 74LS140. Regards Nigel GM8PZR In a message dated 13/01/2013 21:50:38 GMT Standard Time, [email protected] writes:
I want to modify an old HP XTL oven for remote voltage tuning. The HP part number is 0960-0079-1, made by Ovenaire (model OSC 49-14). These were used in HP8443A tracking generators and probably other models too. It puts out 1 MHz, and is powered from +24VDC wrt the case ground. On opening it up I found that the circuitry includes a 74LS73 dual JK FF, and a 74LS140 - very obscure - apparently a dual 4-input gate of some sort. Since there are two FFs available, it appears that the actual frequency of the crystal could be 2,3, or 4 MHz. I'm guessing that it's 3 MHz since there wouldn't be a need for extra gate decoding if it was just a divide by 2 or 4. I will measure and see, but I'd appreciate if anyone has any more info about the guts of these oscillators, so I'll have more to go on for modification and long term maintenance. The fine frequency adjustment is done with a ten-turn trimmer pot, so converting it to remote operation should be fairly straightforward. The divider circuit board is outside of the insulated XO oven, but still goes within the case. It also has the external interface connections and the fine trimmer, so easy enough to get at. I hope I won't need to modify the actual tuning range - I don't want to crack open the oven part. Ed _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
