Bruce Griffiths wrote: > Chuck Harris wrote: >> This is a chicken vs egg sort of problem. When I took apart the oven >> on my 5065A rubidium, it looked to me as though the enamel insulated >> nichrome wire developed a short about 50% into the coil, and wiped out >> the transistor. It also heated the rubidium lamp hot enough to reflow >> the solder on its circuit board and thoroughly char the PCB's epoxy. >> >> I am not sure how the quartz ovens are wound (I suspect they are the >> same), but with the rubidium ovens, the nichrome wire is wound as a >> bifilar loop. This is done for two reasons, 1) to cancel the magnetic >> fields, and 2) to make the start and finish wires of the winding happen >> at the end of the oven where the terminals are. >> >> -Chuck Harris >> >> > An Ayrton-Perry style winding will also have low magnetic field.
There are no doubt hundreds of ways of achieving the same result, but HP used a single layer bifilar winding of enameled nichrome wire that was shorted on the far end. When I replaced the oven winding on my Rubidium, I used a shielded coaxial winding that was also shorted on the far end. -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.