[time-nuts] HP-5065a advise and purchase decision

[Magnus Danielson]

Edgardo,

On 06/30/2012 08:27 AM, Edgardo Molina wrote:
> Dear Group,
>
> Good morning. I wish you well. This is my first post to the Time-Nuts
> group. Please be gentle with the newbie ;)
>
> I have been offered an HP 5065a Rubidium Frequency Standard recently in
> what I feel, a bad operational condition. I need a reliable rubidium
> standard for my time/frequency experiments, still I am in doubt to
> invest in buying such and old beast. The general situation of the
> instrument (for what I have been able to see from the first inspection) is:

> 5Mhz output: Working. sine wave clean but a little bit distorted when
> ramping up. A couple of frequency counters showing 5.0000014 Mhz in
> frequency. No transient pulses or other glitches around the output
> signal. Last digits vary sporadically.

I would guess that you need to trim it so it locks up. Not all that hard.

> No lights coming up when the instrument turned on. No physical damage of
> abuse on case or internal components. No options installed . A couple of
> electrolytic caps replaced on some boards, no trace of burnt PCB traces
> or visible damage to electronic components or physics package. Haven't
> got the manual until today and was unable to check on the front panel
> voltages to check on general health. As turning the voltage test
> selector knob, voltage is shown for most positions, except of course
> battery and the 100 Khz oscillator output. Some voltage test positions
> get the instrument needle to go full scale and out of range, other
> appear to be within scale.

I would assume that the 2nd harmonic is essentially zero, as frequency 
is off, assuming you had a good reference.

> I can perform a second visual and operational inspection today, this
> time with a copy of the instrument manual. I will take my own trusted
> frequency counter and portable digital storage oscilloscope. Would
> really appreciate if I could receive comments from you experts to
> evaluate if such a unit could be worth buying. The asking price is $1K
> USD. Should I consider it an instrument that can be repaired and
> serviced to show some decent performance? Or should I look somewhere
> else to get a decent rubidium frequency standard.
>
> Thank you beforehand for all your kind and expert comments.

I think it is a bit high asking-price for the state it is in, but these 
are quite serviceable and it may take some trimming for them to lock up. 
It's all in the manual. The operation light on one of mine never turns 
on, since the lamp has burned out. This is normal maintenance one should 
expect.

You rarely use 100 kHz today anyway, the only time I use it is to check 
that it works.

cheers,
Magnus