Alternator with new regulator/brushes cuts out at 3500 RPM

My alternator stoped generating (but no charge light while running) so I replaced the regulator/brushes with the kit available here. Now, when I drive around with a volt meter attached to the battery, I see that the battery is being charged until the engine hits about 3700 RPM and doesn't resume charging until the RPM gets below 3400. The cut-in and cut-out RPM remain the same reguardless of what gear the car is in (even Park) or what accessories are on or off (although this does affect the battery voltage a little). My car is a 92 300TE 4-matic with 90,000 miles and an 80 Amp alternator (Bosch 0 120 469 927). When I changed the regulator, I did it from above, by feel, so I could not inspect the slip rings but I did feel the rings, while the regulator was out, and they felt perfectly smooth. The old regulator is definately shot with the brushes short and carboned up. I tighened the almost new belt with the almost new tensioner a little more just to make sure and it didn't affect the cut-in/cut-out RPM. The only thing I can think of is that the slip rings are out of round and that makes the brushes bounce and above a certain RPM they bounce so bad that the alternator cuts out. But that doesn't explain the very abrupt and consistant cut-out/cut-in RPMs. I'm about to buy a new (well rebuilt) alternator. I feel the stock alternator is under powered for the car. I'd like to go at least 100 amp. Will the alternator from a 300SL(Bosch 0 120 468 060) fit my car? Or some other 100 amp or greator alternator? Thanks Jud

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New Alternator fixed it

So I replaced the alernator and it fixed the problem and it was bad slip rings. Even though they felt smooth and looked ok, one was out of round. I think regulator/brushes are a good emergency item to carry (it was enough to get me down the road) and, if you replace them before they go bad, (like every 60,000) then your alternator may just last forever. However, once they,ve gone bad you might as well get a new alternator. Chances of your rings still being OK are probably slim. Unless you could find/make a tool to dress the rings. It would be great if the tool (cutter) could be mounted where the regulator goes and used without removing the alternator. Slap it on, idle the car for a minute, slap on the new regulator, and good to go for another 60,000 miles. I especially cared for being able to replace the regulator from up top, without going under the car or removing the plastic engine pan. I used only a screw driver (philips) and the handy tie wrap to change it. I could have done it beside the road, no problem. Some time when its bright out, take note of where the regulator is and feel around where the 2 screws are. If you know where the regulator is, you can, with a little patience, do the whole job by feel in about 10 minutes. If you end up changing a regulator beside the freeway, jump back in your car, go 80 miles an hour and it dies again, get a jump and stay below 3000 RPM. It will keep going then. Oh, btw, I'd still like to know if there's a more powerful (say 100 amp) regulator that will fit my car. Please.