Dave D wrote:
If you don't have a scope there's a great way to check for ripple on
supply rails.

If the ripple is bad enough, you can set your multimeter to AC volts and
measure the rails. You'll get a slight bump when you first touch the
probes to the rails, but then it should stay at zero. If not, you've
got AC on the rails. I found a very dry filter cap in a Tek scope this
way.

Matt Roberds