[time-nuts] HP/Agilent 5065A Rubidium Vapour frequency standard problem - fixed

Roy Phillips phill.r1 at btinternet.com
Sun May 11 13:08:31 EDT 2008

----- Original Message ----- 
From: "Palfreyman, Jim L" <Jim.Palfreyman at team.telstra.com>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Sunday, May 11, 2008 1:18 PM
Subject: Re: [time-nuts] HP/Agilent 5065A Rubidium Vapour frequency standard 
problem - fixed

> Thanks folks for all your efforts.
> It turns out I was right about the 10811. My replacement 10811 fixed the 
> fault but as Chuck pointed out I was being to much of a cowboy with the 
> course adjustment. Instead I tuned the course control of the 10811 to a 
> reference 5 MHz on the bench and then plugged it all in. This time it 
> worked and it stayed working well too! I've been calibrating the C field 
> over the last 12 hours.
> Now of course I'm turning my attention to the 10811. I would like to fix 
> that!
> With the heater off, the oscillator behaves well with the course 
> adjustment providing the appropriate control (haven't check the EFC yet at 
> this temperature). It is of course below 10 MHz. When the heater is 
> powered it does the right thing (0.5 amp for a few minutes then drops 
> back). The frequency rises to a bit over 10.0000 MHz. However the course 
> control no longer has any effect whatsoever.
> I'm guessing there are some components in the oscillator circuit that are 
> heat damaged after two and a half decades of being in an 82 degree oven. 
> I'm going to follow through the manual and see what I can find.
> However, if anyone has experienced this pattern before - please let me 
> know.
> Thanks again for all your help!
> Regards,
> Jim Palfreyman
> -----Original Message-----
> From: service at frequencystandards.com 
> [mailto:service at frequencystandards.com]
> Sent: Friday, 9 May 2008 4:00 AM
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] HP/Agilent 5065A Rubidium Vapour frequency 
> standard problem
> You didn't really say in your description but you really need to have the 
> loop open using the front panel switch before you try to adjust the 
> oscillator. Unless you are very familiar with how tiny of a turn it takes 
> to make it too far off to lock, you will have it out of range very 
> quickly. Open the loop and connect the 5Mhz output to a good frequency 
> counter, preferably one that is synched to another rubidium, GPS locked 
> crystal or cesium. Once connected, adjust your crystal coarse adjust for 
> as close to 5Mhz as possible. If you can't get it below a 0.1 hz error, 
> you are going to have trouble getting the unit to lock. Make sure you 
> allow a good warm up time for the crystal in the 5065 before you do any 
> adjusting.
> If you can get the crystal to that small of an error, then close your loop 
> and watch the control meter setting. Typical is that the meter will move a 
> small amount but not peg. If it pegs, you have another problem with the 
> unit. If it moves a small amount and stops, you can then adjust the coarse 
> or fine and bring the meter back to zero. If you use the coarse adjust, at 
> this point, you are going to be making VERY tiny adjustments of it.
> Let us know what you find from this and we can move you to the next step.
> Chuck Norton
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