[sdiy] scsi shock

[Happy Harry]

Hi Dave...

The voltmeter is pretty high impedance... it might be that the
120VAC was capacitively coupled through some power supply (line filter
cap?)... and you were high enough impedance to get blasted. If you connected 
a 5K (maybe 5W) resistor across where you measured the
120V... that voltage would drop a lot (if I'm correct)... or not at all (if 
there is a real, hot 120V connection)

Try that (without touching, please... ;^)

H^) harry


>From: Dave Krooshof <synthos at xs4all.nl>
>To: synth-diy at dropmix.xs4all.nl
>Subject: [sdiy] scsi shock
>Date: Tue, 7 May 2002 23:56:09 +0200
>
>Hi list,
>
>I email the list as we had some nice discussions on grounding and shocks.
>Here's another story to share, and questions to ask...
>
>I'm typing with a sore hand, as I just got shocked by my
>image scanner (apple color onescanner) while patching it.
>The SCSI chain is: Mac G3 -> CD Toaster -> Scanner.
>All worked fine this very evening. Nothing got moved a lot.
>
>I just patched the cd toaster back into the chain,
>with both the computer and the scanner switched on. (yes.)
>I was holding the 'outgoing' SCSI cable from the toaster
>and touched the connector on the scanner with that same hand.
>	> Bzzzap! <
>Took a voltmeter, found 126 volts AC.
>The wall socket is 239 volts at the moment (good weather today).
>It's a zero/phase/ground wall socket. All equipment shares 1 socket.
>The scanner doesn't seem to have any short circuits, as far
>as I can see now.
>
>questions are:
>- Why didn't my computer crash, or smoked the SCSI controller
>or simply die?
>- Why didn't the safety ground switch flip? (It does work normally)
>- If a short circuit is there, why isn't it 5, 12 dc, or 230 volts AC?
>(can't test the voltage on the lamp, as it can't be switched on while
>not connected to the mac. No trace of 126 volts anywhere inside).
>
>Any hints on finding the error are welcome.
>
>I'll give my hand a rest, now.
>
>Thanks,
>
>Dave
>--
>____________________________________________________
>And I will make thy windows of agates, and thy gates of carbuncles,
>and all thy borders of pleasant stones. (Isaiah 54:12)
>
>        <Please> no html-mail! html does not belong in email. </please>
>
>http://www.xs4all.nl/~krooshof




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