Antonio- 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 unexpected. 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. Thanks. -Brian, WA1ZMS/4 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of [EMAIL PROTECTED] Sent: Sunday, February 03, 2008 5:42 PM To: time-nuts 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 lock. 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 capacitor on the control voltage line to the varactor. Once replaced the capacitor, the LPRO rose again. So, I would suggest you checking the voltage at the varactor. Antonio I8IOV > 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 _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.