[time-nuts] Re: Sulzer 5B Quartz Frequency Standard Questions

[Bob Camp]

Hi

These standards (and similar ones from various other outfits) were designed for rack mount / stationary use. Things like glass dewar’s for insulation are a fine thing if you are stationary. They are not all that great if you undergo a lot of shock and vibration. ( Also not great if somebody is shipping one of those designs to you via UPS or FedEx …). There are a number of “not so rugged” items like this in the typical designs ….

As a side note: they also “assumed” that power would be applied continuously 24 hours a day, 7 days a week. Fast warmup and fast stabilization …. not a major design goal. 

Bob

> On Mar 19, 2024, at 9:52 PM, Stan via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> Update: I reseated connectors and got the 1 MHz and 100 kHz divider chains working.
> 
> I found that the stiffness in the fine tuning mechanism was caused by a binding turns counting dial. The rest of the mechanism moved freely and to both extremes of rotation when the dial was removed. I disassembled, cleaned, and lubed the dial, and then reinstalled it. Now everything works as it should. I'm letting the standard stabilize before I attempt any adjustments.
> 
> One comment about the fine frequency adjustment. One side of the trimmer capacitor is the copper rod, and the other side is a metal cylinder that has insulation (dielectric?) on the inner surface and is held stationary while the rod advances into or retracts out of it, thus changing the value of the trimming capacitance.
> 
> What stood out to me when I examined this tuning capacitor mechanism is that the cylinder is attached to a short length of stiff wire that is then soldered to a nearby contact on the PC board. The only thing holding this cylinder in position is the stiffness of the wire. Since we're talking about being able to adjust the frequency in 5x10E-11 increments, with a total range of 1x10E-7 given by a travel of the rod of less than 1/2", I would think that any impact, vibration or other mechanical stress might cause the cylinder to shift, thereby changing the trimmer capacitor value. Maybe this standard is only supposed to be used in a vibration-free and stress-free environment, but it still seems like a poor design in an otherwise well-engineered frequency standard.
> 
> Thanks again to everyone for their help with this.
> 
> Stan 
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