[time-nuts] 5MHz ocxo

Paul Flinders paul at flinders.org
Wed Jul 25 21:05:43 UTC 2012


I've finally had chance to pull my Rapco 1804M GPS conditioned 
oscillator apart to try to debug it.

To recap I bought this a few months ago from an ebay vendor. It was fine 
at first (for a few hours) although I needed a better antenna or better 
site for the one I have but the second chance I had to spend any time on 
the antenna the 1804M itself decided to develop a fault running for a 
few seconds then restarting the firmware.

It looks like the ocxo has died - pulling it from the unit and running 
it stand alone produces  a similar result, 10MHz output for a short 
while, then it dies. Presumably this is related to the oven heating up 
and a dry joint or something else that doesn't like getting warm/expanding.

The ocxo in the Rapco is an HCD-66-SC 5MHz 12V unit. They are completely 
sealed and I doubt I could get into it without destroying it so repair 
seems out of the question.

There is a UK supplier of HCD Research ocxo's and although the HCD-66 is 
clearly obsolete, a current unit - the HCD-660 looks about the right 
spec (http://www.golledge.com/docs/products/ocxos/hcd660.htm). However 
I'm pretty certain that if I have to "request a quote" the price will be 
beyond what I can afford to spend fixing the unit.

The only 5MHz ocxo available on fleabay is a Symmetricomunit but the 
auction has no data on it, nor can I find any on the net. It's obvious 
from the photos though that there are a couple of extra pins compared 
with the HCD-66 so it wouldn't fit the PCB.

Does anyone know where I might be able to locate a suitable (used) 
replacement?





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