In article , Uwe
writes:

12V, holy cow!
If I go low voltage I keep it at around 5. I am building a controller board
with basic stamps and recently fried an A/D chip by letting it have 12V, it
was lethal.

Heh heh heh...you low-voltage kids are all alike. Us vacuum veterans
would not think twice about the +120 VDC (the "B+") in the old
"All-American Five" cheap table model AM BC radios.... :-)

By the way, talking about overload. The issue of crystals breaking has been
mentioned a few times, but how do I measure what the crystal "sees" for
current and what is tooo much???

Seriously, folks, the websites for International Crystal, Corning
Frequency Control division, etc., all give specs on various sizes
and cuts of their quartz crystal units. Few really "measure" the
crystal drive levels since that can be done analytically...if one
knows how to do this. If not, there are several hints on the
various crystal unit websites for approximating that, such as
typical circuits.

The best approach at the beginning is to take advice from others
on what works and what doesn't...such as the old, old FT-243
holder crystals can take more power dissipation (thicker slice of
quartz) than most of the smaller HC-6 holder units. The newer
SMD quartz crystal units have very low power specs and should
not be used with most vacuum tube circuits because of that.

Having been in the electron-pushing racket for better than a half
century and bridging the tube and transistor eras, I've never
experienced any quartz crystal physically "breaking." If a
quartz crystal circuit stopped working, the quartz unit just sat
there without a sound, same as it did when it worked OK. :-)
Only the oscilloscope trace knew what was in the hearts of
such circuits...

Len Anderson
retired (from regular hours) electronic engineer person