Great thread. Though no one answered a question I had. Would it be smart to add a safety. This sounds like a royal pain to rewind a heater. I also did not realize you could open the whole assembly up. Not that I want to. But when the day comes with nothing to loose in I will go.
On Sat, Mar 20, 2010 at 10:15 PM, Bob Camp <[email protected]> wrote: > Hi > > You make a tightly twisted pair. The ides is to get the magnetic field to > cancel out. > > Bob > > > On Mar 20, 2010, at 9:14 PM, J. L. Trantham wrote: > > > Do you make a 'twisted pair' and then wind that or just wind two parallel > > wires around the cylinder? > > > > Joe > > > > -----Original Message----- > > From: [email protected] [mailto:[email protected]] On > > Behalf Of Bob Camp > > Sent: Saturday, March 20, 2010 7:59 PM > > To: Discussion of precise time and frequency measurement > > Subject: Re: [time-nuts] HP 5065A rubidium lifetime > > > > > > Hi > > > > I think I can answer part of that, though I've never dissected a 5065. > > > > To make the heater work right you need the proper resistance / foot > heater > > wire. Cupron is a pretty typical material if you want to solder to it. > > Nicrome is fine if you are welding to it. THe real trick here is to find > > somebody with a spool of the right stuff and then beg a few feet from > them. > > > > Doing a hairpin and then twisting is much harder to do right than winding > it > > tightly and then shorting the end of the pair. > > > > The easy way to make the twisted pair is to use an electric drill. Once > you > > wind the stuff, both ends are scrap, but the part in the middle is quite > > good. You loose an inch on each end and get a few feet (or how ever much) > > out of the middle. > > > > Since the maximum temperature the oven can go over ambient rises as the > > heater resistance goes down (good old P = E^2/R) you might put a heater > on > > thats a slight bit higher in resistance than the original. that would be > a > > problem when it gets to 0 (or -20) in you basement, but it would take the > > load off of the rest of the parts. > > > > Bob > > > > > > On Mar 20, 2010, at 8:30 PM, J. L. Trantham wrote: > > > >> Chuck, > >> > >> Can you provide any other information about this repair? > >> > >> How much disassembly of the RVFR, what kind of prep of the lamp > >> casing, how much wire, where did you find the wire, did you 'bend' the > >> wire into a 'hairpin' or did you wind two wires then short one end and > >> feed the power from the other end, what kind of prep for the outside > >> cylinder, what kind of 'jig' to hold everything in place while > >> applying the urethane foam, etc., etc. > >> > >> I have two of these and one arrived dead after which I 'killed' it > >> some more with a total melt down. If this should arise again, a > >> repair guide might be very helpful. > >> > >> Joe > >> > >> -----Original Message----- > >> From: [email protected] [mailto:[email protected]] > >> On Behalf Of Chuck Harris > >> Sent: Saturday, March 20, 2010 7:35 AM > >> To: Discussion of precise time and frequency measurement > >> Subject: Re: [time-nuts] HP 5065A rubidium lifetime > >> > >> > >> I can't say for certain. > >> > >> The heating element is a single layer of formvar coated nichrome > >> wire.... about #36 gage. To avoid magnetic fields, they wound it > >> bifilar, and shorted the far end of the bifilar wires... forming a > >> "hairpin" loop. > >> > >> I found a short about 1 inch into the 5 inch winding, and the oven > >> driver transistor was open circuited. The 1 inch that wasn't shorted > >> was surrounding the area of the lamp assembly. > >> > >> I recall that the oven fuse was ok. > >> > >> -Chuck Harris > >> > >> John Miles wrote: > >>> What was the root cause of the oven failure in your case? > >>> > >>> -- john, KE5FX > >>> > >>>> -----Original Message----- > >>>> From: [email protected] > >>>> [mailto:[email protected]]on > >>>> Behalf Of Chuck Harris > >>>> Sent: Friday, March 19, 2010 9:58 PM > >>>> To: Discussion of precise time and frequency measurement > >>>> Subject: Re: [time-nuts] HP 5065A rubidium lifetime > >>>> > >>>> > >>>> When my 5065A had its oven failure, it got so hot that it melted all > >>>> of the solder joints on the lamp board. I resoldered the joints, > >>>> rewound the oven > >>>> winding, and foamed the unit with some spray can urethane (Great > >>>> Stuff), and > >>>> had it working again for a couple of years. Then something else > failed. > >>>> > >>>> I'd sure like to fix it, but Scott McGrath, representing himself as > >>>> an employee of Harvard University, borrowed my manual more than a > >>>> year ago, and refuses to return it. Oh well! > >>>> > >>>> -Chuck Harris > >> > >> _______________________________________________ > >> 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. > >> > > > > > > _______________________________________________ > > 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. > > > > > _______________________________________________ > 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.
