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

[Julien Goodwin]

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.