Hello time-nuts, A while back I acquired a Tracor 308A (ATT version with 4.94MHz output also) in the hopes of comparing it to the HP5065A and perhaps using it to experiment to improve stability. The two units are the same form factor, use similar sized optical units, have similar electronics, and manuals with schematics are available. Tracor's are notorious for lamp failures (underfilled lamps). However, the lamp on this one did light although it did look a little funky. Try as I might, I just could not get signal through the optical unit. So, I ended up acquiring a similar Tracor 304D unit with the hope of swapping parts and comparing to get one or both working. The lamp in this unit was dead and would not even light. So, I ended up yanking out the lamp assembly and replacing it with one from an FEI FE-5650A (with appropriate mechanical adaptations). After a little alignment it worked like a champ. Next I took the new lamp assembly and threw it in the 308D. And that worked like a champ. So a second new lamp assembly was built up (I have a pile of dead 5650A units). The moral of the story is don't throw out those old Tracor units. I have not run stability tests yet, or attempted any improvements but they make great experiment test beds. I have attached a couple of pictures of the new optical unit and its installation and the two units chugging along and happily locked up. Regards, Skip Withrow