Unfortunately we don't have another G4-like computer that we can test it in. We took it to Computer Warehouse over on Rte 7, but although they had some G4s, they were unwilling to test our power supply in them, since those machines had already been repaired and tested and were ready for sale. We have a couple of places yet to explore though. There's a Computer Warehouse outlet in Beltsville, and also a place that rhiannasilel mentioned. Also, our friend elwing2000 has offered to give us an old one that she happens to have lying around the house! (How fortunate is *that*?). Turns out that the G4 power supplies were really loud, and she replaced it with a quieter one, but the loud one works fine! So Yay! I think the problem is solved.