Philips/Fluke PM 2525 - Replace Battery

[Fuwo]

Hello everyone, I guess I need a bit of an input.

I recently got myself a Philips PM 2525 (my first bench top DMM, will arrive the next few days), and as you do with old tech you go in and check.
Next to greasing the selector wheel gears (motorized selector inside), I also wanna replace the old BR 2/3a 3V Litium battery.

As this battery (most likely) holds the calibration, a simple solder out and in won't do.

So my question to the experienced voltheads:
Would it do to "just" have the system on mains and operating to keep the cal while changing, or will I need to look for points on the board to solder some leads on to hook it up to my bench psu and keep it alive over that while replacing the Bat?

Sorry if this might be a stupid question, I did amplifier recaps, repairs and such stuff, but I never before worked on a cricuit that depended on staying alive while doing so.

[coromonadalix]

you could supply  the meter and do the change,  but you need to have an isolated iron,  some people use  butane based solder irons, some use an isolation xformer,  the iron in some station are 120-220 earth grounded, most of the time its supposed to be fine.

For the calibration holding i dont know, i would personally use an butane iron since i have one.

[Fuwo]

Thanks for the answer coromonadalix,
guess I'll try it with a butan iron, they don't seem to cost that much.