On the FE-5680A, there are two mosfets on the lamp housing - one of them is purely a heater, and the other is the drive FET for the RF lamp exciation signal. I assume the designers figured it was going to run pretty hot anyway and they might as well use the heat for something useful. In practice, the lamp housing temperature seems to be fairly uniform - probably becasue the other end of it is attached in a way (PCB soldered to the heater cup and fibre washers) that gives it a quite high thermal resistance. The lamp is attached to the housing using what appears to be RTV silicone at the base and does not touch the housing at other points. See the attached photo.
The cell cavity has a single MOSFET heater on it and is thermally insulated by a sheet of what looks like FR4 PCB materal at one end and the support for the C-field coil (which seems to be made of similar stuff) at the other end. This sort of level of temperature control seems to be characteristic of small Rb standards based on what I've seen. Regards, Pete On Fri, Dec 2, 2011 at 4:46 AM, Steve . <iteratio...@gmail.com> wrote: > Are there any other (mosfet)heaters on the oven cavity? Seems that heating > from one point is going to create a large temperature gradient which would > probably effect spatial phase congruency. I believe this problem exists on > the two mosfet configuration as well. Anyway, my idea is to remove the > mosfet heaters, wrap my own heater using light gauge nichrome (aka, fuse > wire), mica insulator and build a proper heater/oven assembly. Finally, pot > it all together with some sauereisen ceramic cement. Nice, clean, > controlled gradient. > > Maybe I'm over thinking the whole thing too. I guess I'll find out when I > start my experimenting. > > Steve > > On Thu, Dec 1, 2011 at 9:52 AM, Arthur Dent <golgarfrinc...@yahoo.com>wrote: > >> The referenced photos are poor quality and taken in tungsten lighting >> so you really can't see much from them. Here is a photo I just took of >> a somewhat similar 5650A that may be new so it is still pretty shiny. >> >> http://farm8.staticflickr.com/7142/6436441767_26980890bb_b.jpg >> >> -Arthur >> _______________________________________________ >> 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. >> > _______________________________________________ > 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.
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