[time-nuts] 9390 GPS RX
Mark C. Stephens
marks at non-stop.com.au
Thu May 23 10:21:41 EDT 2013
Hey Ed, Well I have its Ball (just one? ;) Efratom out on the bench.
Seems they built this stuff to service, huh? Nice.
I managed to make a mating connector out of 2.54mm pitch header strip as per your suggestion.
Whew, that was my biggest concern!
Anyway, its after midnight and I have a full day ahead, Looking forward to getting this old gal working again.
I can't help giving the 9390 a reassuring pat every time I walk past it ;)
its sitting there merrily running off the house standard although PDOP hasn't gone below 4 which has me a tad worried.
It seems, I have become quite attached to this 9390 :p
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Ed Palmer
Sent: Thursday, 23 May 2013 1:16 AM
To: time-nuts at febo.com
Subject: Re: [time-nuts] 9390 GPS RX
On 5/22/2013 4:58 AM, Mark C. Stephens wrote:
> It's a 9390-55024
> I have plugged my counter into the Efratom rubidium oscillator thing and disconnected the EFC.
> It is actually wobbling ~ +/-650Hz, peaking as much as +/- 1KHz.
> So, hazarding a guess, something is very wrong inside the black box thing.
Is it really wobbling around randomly, or is it sweeping up and down.
Your counter could be fooling you by taking 'snapshots' at intervals dependent on the gate time setting. If the frequency is wobbling randomly that would likely mean an actual fault in the FRK rather than something that needs adjusting. If it's sweeping up and down, that means that it's searching for the rubidium signal, but not finding it.
Every rubidium will do that, but it should find the signal within 5 - 10 minutes. That could mean an adjustment or a fault depending on the actual frequency range that it's sweeping over. Obviously, you want the frequency range to be 10 MHz +- something.
> My biggest fear is, wherever will I get the 'Winchester' connector used on this oscillator?
That's easy. Improvise! Go into your box of junk connectors and find a female connector that uses pins of approximately the same diameter.
Remove the sockets from the connector body, solder wires onto them, insulate them with tape or heat shrink and slide them over the pins on the FRK connector. For example, RS-232 sockets are a bit big, but could be squashed down. Floppy disk connectors are usually really easy to remove from the body. I'm not sure if they'd work, but you get the idea. It doesn't have to be neat or elegant. It's just temporary for a test.
> What I mean is, for a proper bench job, according to the manual, I'd have to remove the whole rubidium from the 9390 and put it on the clean bench for disassembly.
> Then I can connect various voltmeters to monitor the various signals, and if needed, replace parts and re-align.
> However, I am unwilling to lop off the connector in the 9390, to only have to put it back on/in after Mr. Balls Efratom is back to normal.
> The other way, I suppose is to bodge up wires from the inside of the connector to some sort of temporary Jig for the service job.
> Reading the Most Interesting FRK.PDF, it sounds like the crystal oscillator assembly has issues, whether the crystal oven is broken or similar.
> That is a really interesting document, worth the read, even just for
> the heck of it ;)
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