[time-nuts] HP 5065A questions

Skip Withrow skip.withrow at gmail.com
Sun Sep 25 21:42:50 EDT 2016

Hello time-nuts,
I have recently had the opportunity to play with an HP 5065A rubidium
standard and have some questions.  This unit has been powered down for
quite a long time, it appears to be almost working.  I can see both the
137Hz and second harmonic signals but they seem very low.

In the manual (the one from KO4BB.com) in section 3.9 (pg 3-1) there is a
procedure to apply a 1A current through the TEC until the 2nd harmonic
comes back (due to cell flooding).

1. What the heck is rubidium cell flooding, and how does the TEC in the
5065A fix this problem?  None of the -many- rubidium oscillators that I
have been inside before has a TEC, and I have never seen the subject
The manual suggests that it may take several weeks at the 1A current to fix
the problem (normal operation of the 5065A applies .7V across the TEC).

2. When the coarse oscillator control is swept across 5Mhz (open loop) the
137Hz ERROR signal swings about +/-8 on the meter.  This seems low (and may
be related to this flooding issue).  Just wondering what others have seen
on their units?

3. On page 5-15 of the manual it says to adjust A7R29 for a 2nd harmonic
voltage of 4V at A14(1).  In the section on A14 on page 8-61 the table
states that the normal A14(1) voltage is 8V.  So which is it?  Granted the
2nd harmonic won't extinguish the CONTINUOUS light until it falls to less
than about 1.1V.

I'm also curious about the level of the 60MHz signal feeding the Rb cell.
This unit has several volts of RF, which appears to be plenty, but just
wondering if anyone has any baseline information.

Also, any hints about the care and feeding of the HP 5065A would be
welcome.  Thanks in advance.

Skip Withrow

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