Re: hot scope leads?
- From: "Phil Allison" <philallison@xxxxxxxxxx>
- Date: Tue, 18 Jul 2006 15:14:54 +1000
"RchTop" <rchtop68@xxxxxxxxxxxx> wrote in message
news:1153198903.281411.147850@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
** Groper ALERT !!!!!
I was using my new oscilloscope to look at the heater (6.3v) AC signal
in a simple 12AX7 into a 6V6 SE design guitar amp.
Next thing I know I can smell buring and the ground lead of the probe
is starting to melt.
I turn everything off and barely salvage the scope lead (the ground
lead plastic coating almost melted off, but the main part of the scope
was ok)
I had the scope probe connected like this:
Probe (+ve end) on one side of the 6.3v winding and the ground lead
(-ve end) on the other side of the 6.3v winding.
Anyone know why it would have gotten so hot?
Perhaps I am using it incorrectly.
I am now scared to use it in case I melt or blow it up.
** Err - your scope is grounded at the power outlet and SO is the earth
clip on the probe - hence all readings with your scope are RELATIVE to
earth.
That ground clip must not be connected to a source of AC or DC current which
is ALSO ground referenced as the heater supply is in that tube amp - bet
there is a centre connection going to ground.
Just attach the clip to chassis ground or zero volts on the device's PSU in
future.
......... Phil
.
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