> I've got some that I suspect are not working.  20MHz
> crystal oscillators.  Besides actally trying to use
> them, is there a way to test & see if they are working?

The subject says "crystal" but you say "oscillators". I'll assume
you mean something like an 8- or 14-pin DIL oscillator module

First things first.......why do you suspect they aren't working ?
To have several that don't work seems a little unlikely (not
impossible though, without knowing where they came from
anything's possible)

Do you got a noscilloscope or perhaps a frequency range on
your multimeter ?

You could measure Vcc current

Take a PIC, for example one with working LED-blinky code

Use one as the micro's clock source into OSC1 and see if
the LED blinks at the expected rate

Or feed the oscillator into T0CKI, with s/w detecting TMR0
rollovers to do the LED blinky thing

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