Hi
   I have said goodbye to this one. There are 5 more 5071A with yellow led 
flashing to visit this weekend. 


Regards
LiAng
BI7LNQ
---Original---
From: "Tom Van Baak"<t...@leapsecond.com>
Date: 2016/11/10 06:28:45
To: "Discussion of precise time and frequency measurement"<time-nuts@febo.com>;
Subject: Re: [time-nuts] 5071A with ATTENTION flashing


Hi Li,

1)
When there is a "fatal error" the unit goes back into standby mode, where the 
Cs oven is turned off. Hence the Cs oven temperature error will again be at its 
maximum value (which is that -9.55 number). This is by design.

I use a script to send a scpi syst:print? command once a minute, in additional 
to logging diagnostic information. That way you can see the unit slowly warm up 
and see how each of the readings stabilizes over time. What you may find is 
that the temp error starts at -9.55 and then slowly decreases to zero as the Cs 
oven warms up. If lock is not achieved the oven is turned off and the error 
slowly climbs back down to -9.55. This is by design.

2)
Under ideal conditions a 5071A will lock within 10 to 15 minutes. But if the 
tube has been idle for months or years it can take half an hour or more. During 
this time the ion pump slowly improves the vacuum. So having a log file of 
periodic syst:print output allows you to follow the progress; of the ion pump, 
of the ovens, etc.

The fact that the log has only one entry suggests that someone cleared the 
entire log before you saw the instrument. That's unfortunate. It gives the 
impression the seller had something to hide.

3)
Some comments on the diag information:

> Cs oven is up

This suggests there's nothing wrong with the ion pump or the cesium oven. Your 
oven heater and controller are fine.

> Low Cs beam signal = 3

This is consistent with a tube that's used up all its cesium.

> Raising emult voltage...
> Low Cs signal (37) with max Emult

This is consistent with a 5071 that's trying very hard to get enough beam 
signal, but there just isn't enough cesium left. If a high-performance tube, 
this is expected after 7 to 10 years of use.

> Fatal Error (see Log)

Unlike older cesium standards, the 5071A is quite clever. When there's nothing 
else to do, it does a clean shutdown of ovens and reports a fatal error. The 
unit goes into standby. When I refuse to give up I try powering up the unit 
again and again several times a day.

If I suspect the tube is the problem I swap tubes from a working 5071 frame. 
This is a very simple way to decide if the problem is the frame or the tube. 
After a couple of days of trying, and if the diag messages and fatal errors are 
consistent, then I finally admit defeat and mark the tube bad. The good news is 
you then have an entire frame of spare parts! And also a Cs tube to put on the 
"Dremel" pile!

Finally, remember that even in standby mode, a 5071A makes a very attractive, 
high-quality 10 MHz quartz standard, with multiple output frequencies, with 
high-resolution digital frequency tuning, a LED clock and 1PPS input/output. 
You can turn it into a GPSDO by sending phase or frequency step SCPI commands. 
That is, there's no need for a DAC or EFC; we've talked before on the list 
about the advantages of a DDS-based GPSDO instead of the traditional DAC/EFC 
method.

/tvb

----- Original Message ----- 
From: Li Ang 
To: Tom Van Baak ; Discussion of precise time and frequency measurement 
Sent: Tuesday, November 08, 2016 10:48 PM
Subject: Re: [time-nuts] 5071A with ATTENTION flashing


Hi Tom

I have collected the log from it. Log level is service. The 9.2G pll pass the 
test today. The log during the power-up process is also included.


Regards

Li Ang / BI7LNQ

-------------------------------------



scpi >

MJD        0 02:02:18

CBT ID: 3128A00642(H)

Status summary: Fatal Error (see Log)

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