22 Nov
2012
22 Nov
'12
2:17 a.m.
----- Original Message -----
From: "Eric Smith" <eric at brouhaha.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Thursday, November 22, 2012 5:38 AM
Subject: Re: floating the DUT and isolation transformers
Keith Monahan wrote:
Almost certainly not , the only reason for the live
chassis on a TV was to
avoide the cost of a mains transformer.
Dave
My DUT for the most part is a commodore amiga
that has an external 120v
to +12v,-12v, and +5v power supply. I'm not intending on opening
supplies, troubleshooting/repairing them or generally touching anything
that has live mains power following through it.
Generally speaking, the power supply (internal or external) for any
UL-listed computer (and most others) is isolated from the mains power, so
there's no problem with probing it with a scope or logic analyzer. It's
only when you're working on the power supply itself that you'd be likely
to run into trouble.
A common situation where people have damaged their test equipment is
working on a "hot chassis" (non-isolated) television. I haven't ever seen
a hot-chassis solid-state computer. I don't know whether many tube-based
computers were hot-chassis.
-----
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