[time-nuts] Re: An update on my Efratom FRK with "inoperative lamp"

[paul swed]

Its been a long thread and quite an effort by Julien. We hate equipment
being bad.
Julien
I could have sworn you did get the lamp to ignite. Is that false?
You had heated the lamp up to release the rb that may have plated out on
the wall also. I remember doing that and there was actually a small silver
colored drop that could slowly be moved around. That then vaporized and for
me the lamp did recover.
When they ignite they are one color after 10 minus they change to a
different purple orange color and thats correct for operation.
But know light? Forget the heat. They should ignite with just the rf field.
Regards
Paul
WB8TSL

On Wed, Mar 9, 2022 at 1:22 PM Bob kb8tq <kb8tq at n1k.org> wrote:

> Hi
>
> Adding insulation to an Rb is a very tricky thing. There are
> two heated zones. They need to both be at the correct
> temperature. If the “cold one” gets to hot, things stop working.
>
> No, this isn’t the root cause issue here. If you bulb does not light
> then that’s the root cause. Bulbs do go bad.
>
> Bob
>
> > On Mar 8, 2022, at 8:33 PM, Julien Goodwin <time-nuts at studio442.com.au>
> wrote:
> >
> > As the project has now stalled I figured I'd send another update on my
> FRK with the current state.
> >
> > The FRT:
> > Although the replacement cap I'd picked up (KEMET PEH169MD4470QB2) was
> perfect in two dimensions plus the mounting, it turned out to be way to
> tall. I'll pick up a smaller option at some point (PEH169KB4470QB2 looks to
> be right), but for now I'll just avoid running it for extended durations.
> >
> > The FRK lamp board:
> > The excitation oscillator is absolutely working. I'm still waiting on
> some sensible probing to tune, but it's putting out decent power within the
> right band, which many of you seem to confirm should be fine.
> >
> > After swapping the trimmer back in the heater is absolutely heating hot
> enough, and if anything too hot. I've tuned it back down to roughly right.
> >
> > I don't have any great options for thermocouple probes (just the classic
> K-type beads) so it turns out to be easy to tune things well over if the
> thermocouple isn't making decent contact. Suggestions welcome (although
> non-contact options won't work here, see the next paragraph).
> >
> > New thermal insulation has absolutely helped power usage, not a
> surprise. I filled the lamp cavity, and also put a thin sheet over the OCXO
> cavity, it may also make sense to also add a sheet behind that board, but I
> can always do that later.
> >
> > Sadly, despite all this it still doesn't lock after being left for a few
> hours, and I don't see any light when I look at the lamp (with ~no ambient
> light). As mentioned above I'm not willing to let it burn for a week so
> Darren's suggestion isn't currently practical. I did heat the lamp to ~240c
> early on based on some discussion a long time ago on this list, but that
> was before I'd fixed the excitation oscillator.
> >
> > For now this is stalled until I either pull the bulb out of my house
> standard for a test, or get a parts unit, and thanks to Max for offering
> one the latter may happen soonish.
> >
> > Once again, I appreciate all the experience you've shared while I work
> on this.
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