[time-nuts] Re: New-To-Me HP 5071A Questions

[Tom Van Baak]

Hi Stan,

Well, that's the deal of a lifetime. Congratulations.

1) Send us a copy of the readings. But mostly realize that the 5071A has 
a lot of internal operational integrity checks so if anything is out of 
order it will be the first to tell you. If the green LED is on you're 
good to go.

You can grab a digital summary of the readings by sending the 
syst:print? command via the rs232 port. It looks something like this:

Freq Offset:Â Â Â Â Â Â Â Â Â  0e-15Â  Osc. control:Â Â Â Â  -6.14 %
RF amplitude 1:Â Â Â  27.9 %Â Â Â  RF amplitude 2:Â Â Â  26.3 %
Zeeman Freq:      39949 Hz   C-field curr:    12.170 mA
E-multiplier:Â Â Â Â Â  1318 VÂ Â Â  Signal Gain:Â Â Â Â Â Â  14.4 %

CBT Oven:Â Â Â Â Â Â Â Â Â Â  5.7 VÂ Â Â  CBT Oven Err:Â Â Â Â Â  0.04 C
Osc. Oven:Â Â Â Â Â Â Â Â  -8.9 VÂ Â Â  Ion Pump:Â Â Â Â Â Â Â Â Â Â  0.4 uA
HW Ionizer:Â Â Â Â Â Â Â Â  1.0 VÂ Â Â  Mass spec:Â Â Â Â Â Â Â Â  11.9 V
SAW Tuning:Â Â Â Â Â Â Â Â  1.0 VÂ Â Â  DRO Tuning:Â Â Â Â Â Â Â Â  5.6 V
87MHz PLL:Â Â Â Â Â Â Â Â Â  0.9 VÂ Â Â  uP Clock PLL:Â Â Â Â Â Â  2.6 V
+12V supply:Â Â Â Â Â Â  12.3 VÂ Â Â  -12V supply:Â Â Â Â Â  -12.2 V
+5VÂ  supply:Â Â Â Â Â Â Â  5.5 VÂ Â Â  Thermometer:Â Â Â Â Â Â  43.5 C

You can also get some additional diagnostic information by setting the 
logging mode to verbose and then watch the rs232 port during the 
power-up self-diagnostic and warm-up process.


2) There's no usage or life counter in the tube or the instrument so 
there's no obvious way to know if the tube is new or used, or if used 
once a year, or once a month, or continuously. The 10890A (standard 
performance) tube can last decades; the 10891A (high-performance) tube 
usually gets 7 years if used 24x7x365.

If you plan to run the standard continuously then pay attention to the 
operating parameters by, say, logging them once an hour. Decline in 
short-term ADEV or rise in E/M voltage are the usual warning signs of EOL.


3) My recommendation is not to use the internal batteries. They are just 
a point of failure and decay. The 5071A already takes 120 VAC and/or 24 
VDC from the rear so there's glitch-free power redundancy. I usually 
supply 24 VDC from both a lab p.s. and backup batteries using a diode-OR.

If you really must use the internal batteries, last I checked you an 
still buy the 12V modules pre-assembled. Alternatively you can refurbish 
the ones you have. Each battery module contains six Hawker / Gates / 
Enersys 2.5 Ah Cyclon batteries. Personally, given the value of a 5071A 
(or especially its 10890A tube), I would not substitute with a random 
SLA you have lying around. The Cyclon batteries are another level of 
reliability.

A DIY repair of the battery modules is possible. A spot welder is the 
right way but soldering works too. See page 57 of:

http://leapsecond.com/ptti2020/2020-PTTI-tvb-Atomic-Timekeeping-Hobby.pdf


4) Yes, the hp strap fits that standard sized frame no problem but I've 
never seen someone use it because 5071A are so heavy (75 lbs). I don't 
even like to use the rack mount ears but instead just place the 
instrument on a shelf. The alternative mounting is...

http://leapsecond.com/pages/atomic-bill/

/tvb


On 5/10/2023 5:31 PM, Stan via time-nuts wrote:
> Hello,
>
>   
>
> I just scored an HP 5071A in excellent condition, and to my amazement it
> warms up and locks to the cesium as it should. Here are my questions:
>
>   
>
> 1.	What are the ideal values for the various parameters that are
> displayed on the LCD screen? The Symmetricom manual shows only a range of
> expected values, with no indication of which values are more desirable than
> others.
> 2.	Which of these parameters give an indication of the health/remaining
> life in the cesium tube? The tube is a 10890A, with serial number prefix
> 3839A.
> 3.	The SLA batteries in my 5071A are essentially dead. I'm trying to
> charge them but do not hold out much hope. Are the OEM batteries still
> available? If not, can I substitute a couple of more generic 12V 2.5AH SLA
> batteries, like the Power-Sonic PS-1220, assuming that they will physically
> fit into the battery box?
> 4.	For the trivia experts: it appears that there are attach points for
> strap handles on the sides of the 5071A, but I've never seen a photo of one
> with those handles installed. What is the reasoning behind this?
>
>   
>
> Thanks,
>
> Stan
>