Ed wrote:
My 04E must be less stable than yours. I was monitoring a fully warmed-up Efratom FRK rubidium and saw a drift of ~ 0.04 Hz (i.e. 40 counts) over two hours after I turned on my 1992 from standby. Are more than one type of oscillator used for option 04E? Mine is a model 9462.
There are actually two Racal part numbers that you sometimes see in documentation as being used for Option 04E -- 404386 and 454879. The 9462s in the US military contract 1992s that I have seen (pretty much all of the 1992s one sees in the US are from the mil contract, IME) are marked "9462 454879." I have not seen an oscillator marked "404386," so I do not know if these are Model 9462 oscillators or another model.
As with any crystal oscillator, there is no doubt a range of both stability and warm-up drift in the 9462s you find, but IME not a very large variation. (I'm assuming that you clocked the warmup after the 1992 had been in standby -- plugged in with the red power button "on" -- for a week or more [preferably for a month or more].)
An oscillator with greater warm-up drift will not necessarily be less stable, after warmup, than one with less warm-up drift.
How did you replace the switch guts? Where did you get the parts?
They pull straight out the front, after removing the key cap. We bought new switches from TOKO (the only OEM for that part), but they were retired from production around 20 years ago and I have not seen any available in the pipeline for years now. Unfortunately, the parts units you find for sale invariably have bad switches. I have more than once tried to use switches from a donor unit to repair a 1992, and they have all promptly failed during post-op testing. In one case, six successive switches failed within five presses after I installed them (that was way back before I figured out that you can replace the innards from the front, when I was desoldering and replacing the switches whole).
I hadn't thought about cleaning causing the switch failure. I just assumed it was old age with different brands or lots of switches being made with different recipes for the rubber and therefore different lifetimes.
That was my original thought, too, but I believe the data indicate otherwise. Soldering and cleaning appear to be the next most likely culprits.
I haven't seen a capacitor with detents. Could the fine adjustment be a multi-turn pot?
I assume that is the case -- that is exactly what it feels like -- but I have not disassembled a 9462 to see.
David wrote:
Strange, the fine adjustment on mine doesn't have any detents.
Not surprising -- I assume many of the parts were obtained from multiple sources, and if detented multiturn pots of the appropriate value were out of stock, it would be natural to replace them with their much more common non-detented counterparts. Or perhaps Racal specified a regular, non-detented pot and when a vendor shipped them detented pots by mistake, they used them anyway for one lot of oscillators and I happen to have a couple of those.
The labels on 9462s indicate there were several revisions. I do not know what is different internally between revisions.
Best regards, Charles
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