If you're not comfortable with capacitor swapping, find a good working platinum Mac Plus analog board (if it's pulled from the machine you can tell what color machine it was from by looking at the power switch). The platinum Pluses have sturdier analog boards than any beige pre-ADB machine from my experience.

And yes, the "flupping" noise is a common problem on the early Macs when the analog board fails. In fact, I recall reading a book (Upgrading and Repairing Macs) that used that exact word when describing the noise made by those computers.