Reoccuring error (749) on my HP 34970A

[jogri]

Hi guys,

i've recently bought a 34970a, and nearly every time i start it it shows me error 749 (DMM relay count data lost). The service manual just says "if this error occurs, bring it to Keysight". Do you know more about this error or what causes it? I suspect it's the aging battery (i measured 2.8ish volts) since i get error messages about the time and date being lost when i don't power it up for a week.

[Kleinstein]

The aging battery absolutely makes sense. The dead battery should be replaced anyway and chances are good this would also fix the error 749.

[TheSteve]

It could also be the FRAM, they like to fail.

[jogri]

I found this thread of another member having similar problems:

https://www.eevblog.com/forum/testgear/hp-34970a-error-741-fix/

Sadly, the error on my unit only comes up when the DMM module is installed, so i think the FRAM on the dmm module semi-died (the measurements are still bang on, it just displays this error message every time i start it). The battery is at 2.95V (it has a date code from 1999), i don't know why it lost the date and time.

But as i don't have a programmer for the eeprom and a gpib adapter for reinitializing the new FRAM, there is nothing i can do to fix this error.

[TheSteve]

I found this thread of another member having similar problems:

https://www.eevblog.com/forum/testgear/hp-34970a-error-741-fix/

Sadly, the error on my unit only comes up when the DMM module is installed, so i think the FRAM on the dmm module semi-died (the measurements are still bang on, it just displays this error message every time i start it). The battery is at 2.95V (it has a date code from 1999), i don't know why it lost the date and time.

But as i don't have a programmer for the eeprom and a gpib adapter for reinitializing the new FRAM, there is nothing i can do to fix this error.

I guess this is your chance to buy an eeprom reader/writer. A reader/writer might be able to still read the full contents of the old FRAM. I know mine was bad in the 34970a but the TL866 was still able to read 100% of it correctly. I then wrote it into the new one and soldered it in.

[jogri]

TL866 is on its way, do you know a good method to remove the glued FRAM without damaging it? Heating it won't work as it was wave soldered, do you know if Isoprop can soften it? I don't want to experiment with different solvents and risk killing the board.