HP 54601a failed checksum test

[JacquesBBB]

Hello everyone,

I just got a HP54601a oscilloscope. I tested it for more than one day, and all the channels were working perfectly.
I  made all the internal tests of the machine with success.

Then two days later,  when powered on, it just could not start.
It failed to boot with  the message

illegal instruction : 0H

setup memories failed checksum test - defaults loaded



with nothing more. Impossible to go beyond this  first page.

Any suggestion on what happened ?

Jacques

[rf-loop]

Of course in fail case nothing is absolutely sure until find what is exactly wrong.
But, strong supect: NVRAM internal lithium battery is dead.

[JacquesBBB]

Thanks a lot for the hint.

I see that there is a   DS1220AB  SRAM

Do you mean that I need to change it.  Is  there any HP software on it, or is it safe to simply
change the component, without having to worry about any firmware ? 

Thanks

[rf-loop]

If think this scope age and NVRAM specs it is like final of its life. If it have never changed.

You can run full selfcal and watch if it keep cal and your personal settings and stored things after power off. 

But it is very typical NVRAM battery start fails at these years after manufacture.

In 5450x models NVRAM do not keep any other data than cal data + what user have stored to NVRAM (example swaveforms, settings etc)

I do not know exactly 100% sure how it is on 5460x models.  I have quite strong believe there is nothing else. (because it is HP and related to knowledge about some other HP 80-90 years digi scopes).

[JacquesBBB]

Hello rf-loop,

After your hint, I could search on the web about  the problem of dead battery on a DS1220, and I decided to try
to fix the  HP54601.

The first thing was to desolder the DS1220  (which is not that easy) and to install in place a socket for
future use.
Then I order a new DS1220, but as was impatient to see if that was the  right problem, I tried to change the battery
on the DS1220 following some indications which appear in several places on the web, as
http://www.vk2hmc.net/blog/?p=245

I  use my  proxxon drill to dig into the  epoxy from the bottom,  and manage to remove the battery.
Then I  soldered two wires on the ground and +  former connections of the battery (see photo).
I glued a CR2032  holder  on the top of the DS1220, and put
it back in the socket.

Bingo, it works !

Maybe the calibration is lost, and I will have to do it. This is a nice fix. I would not have known how to start
without your very  helpful comment, rf-loop.  Thanks again.