[time-nuts] Temex rubidium
wa1zms at att.net
wa1zms at att.net
Sun Feb 3 19:29:49 EST 2008
You have a good point. In my case, the varactor voltage as read by
the A to D shows "EF" which is very close to the "FF" max indicated
in the manual. If the temperature of the unit is warm or hot the
unit will lock. But if at room temp or cold the unit will never
reach a locked condition.
I have adjusted the freq trim settings both digital and analog
and just cannot trim the unit any more. Over the past several years
the unit has needed trim in one direction and so it is not
This is a very compact unit and I'm hoping to find a schematic
before I open it. Otherwise, I'll be drawing my own.
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
Behalf Of iovane at inwind.it
Sent: Sunday, February 03, 2008 5:42 PM
Subject: Re: [time-nuts] Temex rubidium
I would report my experience with an EFRATOM LPRO with a similar problem,
maybe this could help.
The sweept frequency was always below 10 MHz, so missing the opportunity to
The sweept VCXO control voltage at the monitor pin was correct, but at the
varactor it was too low. The problem was in a faulty (leaking) SMD ceramic
on the control voltage line to the varactor. Once replaced the capacitor,
So, I would suggest you checking the voltage at the varactor.
> I have a Temex LPFRS rubidium standard that from
> all indications appears to have an internal xtal osc
> that has drifted beyond what the control loop can
> correct for.
> Before I take the unit apart to try and manually trim
> the XO, does anyone has an internal schematic for it?
> (I have the operation/user manual already.)
> Has anyone else done this type of repair on such a model?
> Thanks in advance,
> -Brian, WA1ZMS/4
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