Hi old duke,

pulling off the neg cable is probably not the time-honoured way. But I should add that once the engine is out, you should not replace the cable straight away. Keep it out the way of the battery, switch the ignition off, then replace the cable onto the battery. NEVER do this if the engine keeps running. Same thing here, neg cable out the way, switch off the car, ignition out, then put the cable back on. Otherwise, you stand a good chance to blitz the diodes in the regulator.
Maybe it's just my car but I've had to intervene a number of times on my 240 (1993) because of electronic-related problems, and this certainly seems to be an issue on BB. And electrnic-wise, I'm a caveman. But I learn. However, I'm convinced that compared with other makes (especially French and Italian), and the stellar mileages achieved by a lot of people in old Volvos which take a lot of components to limits never reached before, our tanks fare rather well. I think it's part of the philosophy of running an old Volvo : repair rather than throw away. I do, even if the car's worth little. Time and efforts are secondary, most of the time. It's part of the ethos.
Happy cruising

Pierre