Charging problem

[celicaboy1990]

So I'm basically new to this site and I know what your all thinking another nueb that doesn't know his ass from his valve cover. I've been on alltrac.net more than any other forum but I needed help with my supra for the first time. Basically I'll lay it out, I have a 1990 toyota Supra 7mge automatic with 181010 miles on it. Recently before I was going to sell it something happened. I got back from the shooting range and my car and a terrible time starting and started revving wildly, up to about 2500 3000 before dropping and doing the same. I thought this was weird. I was told by my father to charge the battery to reset the car and to park it and rev it up to a clear what ever was wrong with it. It's seemed to work because he's heard of the revving problem before. I was wondering though why the car was dead though?.. So I basically charged the battery and thought it was a freak thing. On my trip to up north though my voltage started to drop and I got stranded. After limping the car to a repair shop he tested the out going plug from the alternator and said there wasn't any voltage coming through it so it must have gone out. I was like alright got a new alternator assuming that was my original problem. After replacing it I seemed to work till I took an hour and half drive home and I saw the voltage slowly going down again. I parked the car took out the alternator and had it checked. They said it was good so I threw it back into the car and charged it up again. it runs for awhile but soon dies and the battery is basically new also. Can anyone help ?

[SupraTuned]

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[ddouglas77]

Have checked for voltage at the alternators voltage regulator, I had a very similiar problem.