Thanks. That is just the type of information I was looking for.
I have some pictures of my 'melted' unit with the covers off the end of the cell end if anyone is interested. It is pretty messy after the meltdown. There are at least three metal cylinders for sure, an outer one then foam between it and the next one, then foam between the second and third one then foam inside that between the inner cylinder and the aluminum cylinder that is the rubidium lamp assembly. When I started trying to disassemble the unit, I could not get the aluminum cover of the lamp assembly to turn loose. I replaced the three 2-56 screws that hold the cover in place with longer ones then used a 1/2 inch thick aluminum disc with a center hole placed over the center bolt of the lamp assembly, resting on the long screws. I used one of the nuts and 'torqued' it to 'pull' the cover off the lamp assembly cylinder but to no avail. However, after the melt down, with everything 'hot', it came off relatively easily. This is what makes me think it had had a prior 'meltdown' and the 'goo' had dried as an incredibly strong glue. Although mine was destroyed, it did not appear to have a 'twisted pair' type winding but rather a single layer. I had missed that it was a 'parallel pair'. Thanks, Joe -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chuck Harris Sent: Saturday, March 20, 2010 11:38 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] HP 5065A rubidium lifetime Hi Joe, The original winding was wound with parallel (non twisted) bifilar wires. The two wires at the entrance to the winding went to the oven circuitry, the two wires at the exit to the winding were shorted, thus forming the "hairpin". There were hundreds of turns of wire tightly wound in a single layer. I recall that the wire was about #36 AWG. I replaced the winding with some coaxial heating wire that I found someplace. It has been something like 25 years since I did this. As I recall, HP wound some Kapton tape on the aluminum oven assembly, and then wound the nichrome wire over the tape. The whole assembly fit loosely in the mumetal can that encloses the entire physics package. They expanded some kind of foam in the space between the assembly I knew the oven was shorted, and I had little to lose, so I just pressed the assembly out of the can. This exposed the oven winding. When I foamed the oven, I used a couple of wooden wedges to hold the aluminum oven centered in the shield. I seem to recall that there were two mumetal cans, with foam between them. One had a tuning solenoid winding, and the other had a heater winding. All of this is pretty foggy... -Chuck Harris _______________________________________________ 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.
