Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!samsung!uakari.primate.wisc.edu!ames!amdahl!key!jbr
From: jbr@key.COM (Jeff Rubin)
Newsgroups: comp.sys.mac.hardware
Subject: ADB and blown motherboards
Summary: When is it safe?
Message-ID: <1494@key.COM>
Date: 1 Mar 90 20:10:22 GMT
Reply-To: jbr@hongkong.key.COM (Jeff Rubin)
Organization: Key Computer Laboratories, Fremont
Lines: 21


It was reported by several people that it is unsafe to plug and
unplug ADB devices when the Mac is powered on.  Some have even
reported blown chips on the motherboard that were attributed to
this type of manipulation.

I'm not sure which machines my question pertains to, so I will
phrase it in terms of my Mac IIcx.  The keyboard (Apple extended)
has a button with a triangle on it that I use to turn the power
on.  Since the keyboard is an ADB device, does the power-on
mechanism use the ADB?  If so, does this imply that ADB has power
even when the rest of the machine doesn't?  Does that mean that it
is not safe (just as unsafe?) to plug/unplug ADB devices when the
power is off?  Do I have to pull the plug from the wall before it
is safe?  Is there a big capacitor on the power bus?  How long do
I have to wait after I pull the plug from the wall?

Inquiring minds want to know ... and I do too.
------------------------------------------------------------
Jeff Rubin
...!amdahl!key!jbr