[R-390] Capacitor tip

[wli]

Here is a tip re checking caps that we all once knew, but probably forgot.

Bypass caps can be checked in a live circuit with a scope. By checking the ungrounded lead of the capacitor in question, there should be no AF or RF signal. If there is anything, the cap is either  open or its ground connection is open. Of course, a shorted bypass cap results in a loss of the normal DC voltage at that point.

Coupling caps should the exactly identical AF or RF signals present at both leads. A leaky one will show abnormal output voltages.

W. Li 
Mercer Island, WA