Got this very clean 8600a for $10 at a hamfest yesterday, and rather than clutter the TEA thread I'm making a separate one to track the repair/conversion.
I have an 8600A already, and it's possibly my most used bench meter; all the features I need, and plenty accurate for audio work. So adding another at such a great price was a no-brainer. But the battery operation is frankly of no interest to me; I have plenty of portable DMMs and having to disassemble a meter just to periodically replace fussy old NiCd batteries would be a distraction, particularly when I have to extract it from a stack of other gear on the TE shelf to do so. Of course I checked the forum for existing threads on the subject:
https://www.eevblog.com/forum/testgear/fluke-8600a-battery-power-supply-conversion/and learned that I shouldn't power it up without the batteries installed. One of the batteries is kaput, and the 5VDC is only about 4.3V even when powered off the AC line. In spite of this, DCV is fairly accurate; but ACV is way off and Ω is very flaky. Some of this may be dirty switch contacts but until I get solid power to the unit I really don't want to do more than clean the switches and inspect for obviously damaged components. The cal sticker was still in place from 1974, so it's likely that the meter was retired without ever being opened or tweaked.
It looks very clean inside; even the battery leak was contained by the plastic holder and nothing got onto the board. So there's nothing shouting "replace me". OK, maybe the tantalums are whispering a little, but again until I get power to the board, I'm not listening.
The big question (addressed in the link above) is how to go about supplanting the battery power. Xrunner did a nice total replacement of the supply, and others have suggested I just drop in replacement batteries and be done with it. I'm favoring replacing the batteries with a cap and some form of LDO regulator, to minimize power dissipation and give the inverter a stable input. The transformer is a different model, not designed to run the same regulator setup that the line powered unit has, so I'll either have to do this or replace the whole PSU.
Right now, the first step will be to disconnect the PSU from the rest of the meter so I can see how much voltage I have to work with and not fry anything in the process. Then I'll see what my options are for a rugged 5V regulator and proceed from there.