1976 Toyota Corona alternator problem?

Electrical problem
1976 Toyota Corona 4 cyl Two Wheel Drive Manual

Hi there I has a 1976 toyota corona. I'm having issues with the charge light that comes on from time to time. When it comes on bright red, My car doesn't have much power when I'm driving, it feels like it wants to die, but at times when I start it up, the light will come on not as bright, and it runs just fine. Could this be the alternator? Because recently I changed the alternator belt, because the other one was cracking, but it's on there now tight but still have issues. Can you help, thanks.