datron-wavetek 1271 NVRAM

[guenthert]

I just acquired a datron / wavetek 1271 DMM, which seems to be in good working condition (I'm neither qualified nor do I have the necessary gear to determine, whether it is within specifications, but it seems to be fairly near at least, despite being some 25 years overdue on its regular calibration 

There's a cal. sticker from '93 over one of the chassis screws, so I must assume replacement of the battery is some 20 years overdue as well. 

The sensible thing would be to replace the battery and send it off to calibration, albeit I'd rather postpone this until I'm cash-flow positive again.  The manual recommends exchanging the battery while the unit is powered on.    I'd like to preserve the NVRAM content with the calibration data as is, while exchanging the battery.

I was wondering, whether someone figured out how to read out (and latter write, if necessary) the NVRAM using GPIB?

[Mickle T.]

Wavetek/Datron 1271/1281 do not have this capability

[ap]

My recommendation would be, based on work done on many Datrons such as the 1281, 4920 and so on, to replace the battery in power-on mode. Be carefull doing that, cut the wires and carefully solder in a new battery, with either the solder iron or the Datron NOT referenced to ground (floating). This way unless you short something, nothing should happen. This is also how the manual suggests it. And you will kepp cal data integrity. I have seen quite a bunch of meters having problems with the SRAM; if so, you have lost cal data anyway and would get an error message.

[alm]

Temporarily putting a secondary battery in parallel with the battery you are replacing is another possible safety net.

Instead of floating either the meter or soldering iron, the trick I used was to put a fairly large tip on the iron (large heat capacity), and unplug the iron from the station just before touching the terminal. Then solder/desolder one terminal, and plug the iron back in to heat up. Rinse and repeat until the new battery is in.

[guenthert]

Wavetek/Datron 1271/1281 do not have this capability

Hmmh, yes, what a pity.  One would have thought that such might be helpful at least in the development phase.  I was already afraid that this feature is not available in released firmware versions or not documented.

Thanks anyway.

[guenthert]

So I just replaced the battery feeding the NVRAM (*) while having the unit powered on -- brrrh, the battery is near the power inlet, and the tabs were crimped first, then soldered, making the procedure more difficult then necessary -- I ended up cutting the old wires.  Date code 10/93 and still more than 3.6V on the old one.  The manufacturer of the battery expects them to live up to 10 years, Datron recommends to change them every 5 years, but how long can they actually last (did any ever die  ) ?
Operation seems to have been successful (full test completed successfully) and at least a brief power interruption when moving the unit back on the shelf didn't destroy the NVRAM content. (where's the sweaty emoji?) Important to me, as I got the unit for less than calibration would cost...

*) Glad I kept my old Radio Shack fire starter, as that one has a high impedance to ground, unlike my new Hakko soldering iron.