[time-nuts] Temex LPFRS-01 / LPRO rubidium reference repair

Ed Palmer ed_palmer at sasktel.net
Sun May 26 14:37:11 EDT 2013

I don't have an LPFRS, but if I'm reading the manual correctly, the 
fourth column of numbers on the 'M' command (4D, 4C on your screen 
capture) is the VCXO control voltage.  Shouldn't this be continuously 
sweeping up and down until it finds lock?  Does the output frequency 
sweep up and down and is 10 MHz somewhere in the sweep?

I think that the second column (Rb Level) will only be valid after the 
unit locks.  The first column (Photocell DC voltage) shows that you've 
got lots of light from the lamp.


On 5/26/2013 11:43 AM, Gerd v. Egidy wrote:
> Hi,
> I bought a used Temex LPFRS-01 / LPRO from fluke.l on ebay. Unfortunately the
> unit is broken and shows the same defect as was mentioned about a year ago on
> this list: after warm-up it locks for a few seconds, but lock is lost again
> after a few seconds. The lock output pulls low for a few very short intervals
> afterwards, but that's it.
> I got a refund (but excl. the VAT I had to pay at customs), so it's just a
> small loss. But of course I want to try to get this thing alive again.
> In the post last year it was mentioned that these used units suffered from some
> kind of water damage inside. So I opened up the unit, but it looks clean
> inside. Just very small signs of surface rust on the screws and connector.
> Here are some teardown photos I made:
> http://www.egidy.de/temex_lpfrs_lpro/
> I have connected the serial terminal. When using the "M" command for
> monitoring, the unit returns detailed data. The rb signal level is too low on
> my unit, see the screenshot at the link above.
> Was anybody here already able to fix such a unit?
> Any ideas what to look for or other insights?
> Kind regards,
> Gerd
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