I hadn't thought about the uA739 for a while. It was one of the
original low-noise amps - we used to use it for phono preamps.
Re: glass piston caps, I have been able to sometimes get what I need
from Surplus Sales of Nebraska
<http://www.surplussales.com/Variables/PistonTrimmers/PistonTrimmerCapsIndex.html>.
Perhaps something that small would not be too bad for shipping.
Regards,
David
On 6/5/13 7:29 PM, Mark C. Stephens wrote:
Talking about punishment, I pulled the old 9390 out yesterday and plugged it in.
Up the GPS came, but after 8 hours, still no lock LED.
(the lock LED is directly connected to Mr. Balls FRK).
So I thought, bugger, Well I have the Jig made up, I'll have a look at it on
the bench.
So I removed it and while I was removing the Mu Shield I noticed a missing
screw in the baseplate.
I bet you can almost hear the hmm..
I checked the rest of the screws, they were all loose!
So after a quick perusal of the Manual, I removed the bottom plate.
Well, the Pot that controls the temperature is still there - sort of.
The top half is missing! There is basically a 5K resistor there.
Methinks, I suppose that's half the problem, then.
Poking around amongst the foam I spot the lovely glass piston cap for tuning
resonance.
It is all scratched and loose. I'd say a bump would move it.
So, I replaced the Pot, but I dunno where I am going to get one of those
trimmer capacitors from.
I poked around for a while comparing notes with the manual and I find my
schematic doesn't match my servo board.
Mine has a different front end op amp, pin outs and everything are different.
My schematic has a OP27 but the board has a ua739.
Also, the voltages etc seem wrong on E1 and E5, I got a 30-45Mhz, 40mV sinewave.
Nothing on TP1
And a Nice 125Hz signal on Tp4.
I've gone and shelved it again as I want to get rid of some other projects.
I also noticed my Austron is stuck in a reboot loop.
Gets to all the way to checking failsafe ... something and then spontaneous
reboot.
Sheesh, I don't seem to be having much luck lately with these old chaps.
All I ever wanted was a half decent Rb GPSDO!!!
RDR-Electronics have heaps of stuff I'd grab in an instant but they won't post
to Australia.
RDR Won't budge an inch despite my begging. ):
I think I have a acquaintance in USA that can maybe help but the shipping is
going to kill me to death..
-marki
-----Original Message-----
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf
Of Ed Palmer
Sent: Monday, 3 June 2013 6:24 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Cheap 9.8Mhz Sa.22c's
Glutton for punishment, aren't you Mark! :)
There's probably no way to get to 10 MHz. I have two of these that I picked up
just to play with. Another purchaser contacted Symmetricom and actually got
some information out of them. The oscillator in these runs at 58.9824 MHz.
The default output is 9.8304 MHz. The output can be changed, but only in
submultiples of the 58.98 MHz. e.g. 58.98 divided by 6 equals 9.8304. You can
change the '6' to various integers as documented in the manual.
To move the output to 10 MHz you'd have to change the crystal back to the
standard 60 MHz so that you could divide it by 6. But then you'd mess up the
multiplier that takes the crystal frequency up to the Rb frequency. You'd have
to change the synthesizer that controls that side of the system. There's no
way to tell if that would require a completely new firmware load or if, just
maybe, there could be an undocumented (maybe protected) command to modify it.
You might be able to send it back to Symmetricom to get it changed but, based
on my experience, you couldn't afford it.
Ed
On 6/2/2013 11:52 AM, Mark C. Stephens wrote:
These are 9.8304Mhz, is possible to move them to 10Mhz?
http://www.ebay.com/itm/Symmetricom-SA-22c-9-8304MHz-Precision-Rubidiu
m-Oscillator-5V-and-15V-NICE-/261223397404
-marki
Kind Regards,
Mark Stephens
Mark Clemens Stephens | Customer service engineer | Non-Stop Computer
Ltd
* +61 2 9011 8186 | ( +61 428 256 334 | *
ma...@non-stop.com.au<mailto:ma...@non-stop.com.au>
Non-Stop Computer PTY LTD
79 Devon St
North Epping
NSW 2121
Australia
Timezone: AEST (UTC +10)
Email: serv...@non-stop.com.au<mailto:serv...@non-stop.com.au>
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