The data sheet for the 1000B is available on the Symmetricom website. The pinout is not given. Here is the pinout. 1- Electronics return 2- Control voltage in -10 to +10 VDC 3- Coarse tune in voltage 4- +12VDC reference out, coarse tune hot 5- Oven return 6- Oven monitor 7- +24VDC oven power 8- +24VDC electronics power 9- Case ground On some units the internal coarse control is disabled and the pot is brought out to the instruments rear panel to allow adjustment without disassembling the unit! You can tell if this is the case if wires are connected to the mainframes connector on pins 1 3 and 4 and finding the pot at the other end. These 1000B have pins 3 and 4 as shown. In this case pins 1 and 4 connect across the pot and the wiper goes to pin 3. The pot on the 1000B will not have any effect. Hope this helps. Corby Dawson After some comparisons against my 1000B I swapped the oven controller card and the oven current came back! Further tests isolated a bad .01ufd capacitor on your controller board (shorted with a reading of about 400 ohms). After replacing the cap and putting it back together The frequency could not be adjusted to center so I pulled it apart again and adjusted the trim cap on the oscillator board. This got it close but still not right. Then I determined that the frequency adjust pot available thru the front panel was not connected internally! Your unit is configured for an external pot. I connected an external pot per the data sheet and with zero volts on the EFC pin was able to use it to adjust to center frequency! Whew! After a weeks warmup to get the aging out of the way your 1000B was tested to evaluate its short term stability using its 5Mhz output. Attached is a plot of the measured data.