Joe, Your unit could be a 916 prefix with the newer physics package and 10811 added as retrofits.
Look at the top of the A3 module, what is the series number? Also look at the A9 op-amp module, does it have a Epoxy block op-amp or a transistor can style op-amp? What serial number is penciled in the data log on the front panel that swings open? Last year sold was 1992 and latest serial number prefix was 2816A. With the unit in lock adjust the Oscillator fine freq to mid range and the coarse for a reading of around zero. Red lamp is not stock, the green one probably broke and that was only one they could find! Like Dan said the top cover is covered in holes and is hard to find. If you find a bottom that fits make sure you cover the inside with insulating tape. The original bottom cover has a very thin phenolic insulator covering its inside. The switch Paul mentioned is for the 1Mhz and 100Khz dividers. the rational was that if you had a power hit the clock would stop (the 1Mhz also drives the clock option) making sure you were not using a bogus time. Just leave it in the auto start position! The logic reset button is the one that will turn on the operate light! Cheers, Corby _______________________________________________ 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.