Some pix of the rg would be great On Wed, Apr 25, 2012 at 11:43 PM, Ed Palmer <[email protected]> wrote:
> Paul, > > Good suggestion, but I don't think pop rivets had been invented when they > built this thing! :-D It's built like a piece of mil-spec equipment. > When I google for individual parts, I keep tripping over NSN numbers. Now > that I look closely at it, I realize that the case is just the case with no > electrical connection between it and the circuit other than the BNC jacks > on the front panel. The concept of 'chassis ground' is an unknown concept. > I don't think there's even one chassis ground lug anywhere. Even when I'm > poking around inside the unit, there are no live wires that I can touch, > everything is insulated. The build quality is very high. > > But now that you've got me thinking about it, I think there's something > weird about the grounding in the physics package. I've got to take another > look at that. > > Thanks! > > Ed > > > On 4/25/2012 8:59 PM, paul swed wrote: > >> Ed look for pop rivetted ground logs. Famous for going bad. HP even used >> them. >> Drill em out and put real bolts and lock washers in >> >> On Tue, Apr 24, 2012 at 7:34 PM, Ed Palmer<[email protected]> wrote: >> >> Paul, >>> >>> >>> On 4/24/2012 5:24 PM, paul swed wrote: >>> >>> When all else fails check the grounds. Especially 40 year old screws. >>>> >>>> Been there, done that. This unit had multiple problems with bad >>> soldered >>> ground connections. I went through the unit and resoldered everything >>> that >>> looked the least bit odd. I didn't find any screws that were >>> electrically >>> significant. Maybe I should look again! >>> >>> Ed >>> >>> On Tue, Apr 24, 2012 at 6:13 PM, ed breya<[email protected]> wrote: >>> >>>> Ed, >>>> >>>>> Tuning the cavity should peak everything - it just maximizes the >>>>> excitation power at the microwave frequency, so you get the most output >>>>> from the Rb light wavelengths. A mechanical cavity resonator will have >>>>> a >>>>> very wide (compared to the modulation frequencies you're looking for) >>>>> bandwidth, so unless something happened to it physically, it should be >>>>> OK >>>>> as originally built or adjusted. However, you may want to look at the >>>>> multiplier chain and SRD bias circuit components and adjustments - >>>>> those >>>>> could have drifted quite a bit over forty years, limiting the microwave >>>>> power due to being off-frequency, or having poor multiplication >>>>> efficiency. >>>>> >>>>> I'm guessing that the second harmonic is indeed present, but just >>>>> buried >>>>> in the noise, and the loop still can "lock" because of the further >>>>> signal >>>>> processing, even though you don't see the evidence - remember it's a >>>>> lock-in amplifier capable of digging a tiny signal out of the noise. If >>>>> you >>>>> go through the multiplier and check and tweak things, you may get more >>>>> excitation power and signs that it's getting back to normal. Once you >>>>> get >>>>> enough power, if the Rb cells are still good, the second harmonic >>>>> signal >>>>> should show up large enough for the circuit to detect sufficient S/N >>>>> ratio >>>>> and provide a valid lock indication. >>>>> >>>>> Ed Breya >>>>> >>>>> >>>>> Ed Palmer wrote: >>>>> >>>>> Could the drift be at least partially responsible for the lack of >>>>> second >>>>> harmonic? A message on the list ( >>>>> <http://www.febo.com/******pipermail/time-nuts/2006-****** >>>>> April/020562.html<http://www.febo.com/****pipermail/time-nuts/2006-****April/020562.html> >>>>> <http://www.**febo.com/**pipermail/time-** >>>>> nuts/2006-**April/020562.html<http://www.febo.com/**pipermail/time-nuts/2006-**April/020562.html> >>>>> >**) >>>>> said that you could peak the second harmonic by adjusting the cavity >>>>> tuning. >>>>> If the cell and the cavity are out of sync would that kill the second >>>>> harmonic? How close to they have to be? If this thing has a cavity >>>>> tuning adjustment I haven't found it. >>>>> >>>> > ______________________________**_________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/** > mailman/listinfo/time-nuts<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.
