Hi

A bit of digging into the error messages probably is in order. The 5071A isn’t great
in this regard so you only can get some of the data.

There are two basic possibilities:

1. It’s some sort of random failure. Corby is your best bet here.

2. Far more likely, It’s the tube. Cs tubes only last just so long. If yours has the high
   performance tube option, 5 to 7 years of operation is about all they are good for.
   The only known source for proper replacement tubes is Symmetricom / Microsemi
   / Microchip in Beverly Mass.

Last time I had to do a tube replacement, cost was right at $40K. That was many years
ago. My guess is you probably can add at least $10K to that number. That’s only a guess.

Properly shipping a Cs (as in shipping it back to get fixed) is complicated. If you do the
legit thing and label it as Cs / Hazmat there are a lot of hoops to jump through. The
person doing the shipment needs to have the proper training and credentials. I know this
sounds strange, but that’s how it works.

Fun !!!

Bob

See pages 2-15 / 2-16 in the operation & programming manual
(05071-90041). You want to set the diagnostic log level to "service",
configure the RS232 port, and run a terminal program on a PC to view or
capture the results. Power cycle and watch it until the end. Repeat if
necessary.

You will get a step-by-step account of the warmup and locking process.
This diagnostic information is very informative. It will help decide if
you have a temporary, minor, and interesting problem or if you need a
new CBT (Cesium Beam Tube), which is to say, you will either have a fun
problem to share or a very bad day.

Feel free to post the log files. A number of us have 5071A and can help
explain your results.

/tvb

On 2/3/2021 10:35 AM, Jeff Sanders via time-nuts wrote: