As you have replaced the brushes I would guess that the problem is now solved. I'd give the bike a run, maybe 30 miles or so and then remove one of the pickups and see if there is any noticeable change in condition. If everything looks OK stop worrying! After all, there's no point in having an old bike and not using it. In the UK we have breakdown insurance so the worst case scenario is we get driven home in pickup!
Regarding slip rings generally (sorry if this is repeating previous posts) I use the black plastic slip rings which seem to have superb anti-friction characteristics but also they're not brittle. The original Lucas slip rings can have hair-line cracks which are difficult to detect. I saw the white, self assembly ones, at Stafford a few years ago and thought they were a good idea but they were very expensive. It appears now, from this thread, that the material isn't as friction proof as the black ones.
Regarding brushes, the original Lucas brushes had a fine groove down their length and a very light spring. If anybody has brushes like this, provided they are serviceable, I would advise sticking with them. I've had no problems with the replacement brushes from Wassells except that the springs are a bit heavy and short so, when fitting, it is necessary to make sure they are contacting the slip ring properly. However, these brushes are not the same as the ones supplied with Wassells pickups. I find these brushes to be much too soft, i.e they fail the graffiti test!, so I always chuck them away and fit the better quality brushes which I know are OK because I use them in my own bikes. It's weird that Wassells supply complete pickups with cr4p brushes yet sell perfectly good brushes separately! When using the replacement brushes I always rub their tips on some ordinary paper before fitting to clear away any loose particles and remove roughness from the surface. After a bit of a polish they leave no marks at all.
