cal ram checksum error (HP 54501A)

[zolauri]

hp 54501a

My question is mainly for HP 54501A digit scope users or experts who are familiar in calibrating and fixing this modell, but every useful advises are appreciated.

I have a digit scope (HP 54501A) and there is a strange failure with it. After every single startup I get an error message "cal ram checksum error, re-cal instrument"

After re-calibration the scope works good.

If I ignore the error message and run the SELF TEST with TEST ALL option the following three lines returns with result "FAILED"

1.Protected Non-Volatile RAM
2.D/A converter
3.A/D converter

When I recalibrate the instrument (Util menu>Self Cal) the scope can be used again. What's more, if I run the Self Test _after_ recalibration all the lines returns with result "PASSED" even the mentioned tree. Since the problem appears _only_ after turning off and on that's why I think that is caused by a backup battery.

The question is: Is it an easy to handle tipical failure (broken backup battery or something like this) or it signs a more serious problem?

There is an important additional info. The scope had been out of use for about 10years at least when I turned it on last week.

thanks in advance
z.lauri

 

[pit]

cal ram checksum error re-cal instrument

Hello!

I am not familiar with this specific device, but HP devices of that generation often had a battery backup RAM (aka NV-RAM) with Li battery. Look inside if you can see something like that.

There may also be a external battery which is exhausted now.

You can replace the NV RAM module as a whole part, or you can rip off the battery and solder an new one on top of it. Look for Sun Sparcstation 5/10/20 NV RAM replacement/repair procedures, they have a similar problem.


CU

 

[zolauri]

hp 54501a repair

I took a closer look inside the instrument. I found this

**broken link removed**

ram in it.

Im almost shure that the litium cells inside the package are broken. Since this IC isn't available in my territory I will have to try to replace the cells.
Since I didn't find any detailed description about the structure of this IC so I dont know what can exacly be found in the package. Can this package be disassembled and can the cells be separated from the chip?

Has anybody ever met such problem?

 

[pit]

hp scope nvram error

Hello!

Looks like the usual NVRAM with exhausted Li cell.

The easiest way to replace it is to order a sample from Maxim. This may take a few days, sometimes it takes several months or a year. Recently I got samples that I have ordered about half a year ago...

The other way is to repair it as I already wrote, look for the Sun NVRAM repair docs on the net, for example:
<http://www.squirrel.com/sun-nvram-hostid.faq.html#attach>


CU

 

[MinMin]

hp54501a calibration procedure

You have to locate a swith for CAL/NORM and set to CAL then cal. again.
If this way can not get to work, Use a general porpose SRAM with Li batterys and diode. All the pinout exact to NVRAM.