[Ti] Painful shocks from Ti

[Jerry Krinock]

on 05/03/22 15:46, John at simplymail at ururk.com wrote:

> Should I be feeling painful shocks when my arm is touching a bare
> portion of the frame on the outside of the Ti? I only feel them
> strongly when my foot is resting on the heating duct register, and it
> seems only the bottom of my arms (between hand and elbow) feel it
> strongly.
> 
Here's something I wrote up around May 2004 but never sent....

Many have reported on this list receiving electric shocks from touching
their titanium powerbooks.  I have noticed this, and, for a couple years,
thought I was imagining things, that it was in fact something to do with the
texture of the paint.  But a few months ago I began using my powerbook on an
electronics lab bench, often touching it and other grounded equipment, and
after a few days realized that I the jolts I was feeling were not my
imagination.

Since I am spiffing up this powerbook to pass on to my wife and telling her
what a great machine it is, I thought I'd better investigate!

I bought my 800 MHz DVI powerbook used about a year ago, and with it,
instead of the white brick, came two of the old model M7332 YoYo AC
adapters.  From past experience, I knew that these adapters should have a
center prong on the DC (computer-end) plug which sticks out farther than the
outer ring.  For some reason, the previous owner had cut off these center
prongs so that their end is flush with the edge of the outer ring.

I also have a Madsonline model ZCV45FS24S48 45-watt converter, and a new
Apple which I just received with my 1.5 GHz aluminum powerbook.

For each power converter, I first made three measurements, from any of the
three conductors of the DC connector to the building ground, with the
adapter plugged into the wall:

a) AC waveform , viewed on oscilloscope
b) AC voltage to ground, measured with Fluke 77 multimeter
c) AC current to ground, measured with Fluke 77 multimeter

In all cases, I found that the measurement from two of the conductors of the
DC connector was the same, and also that this voltage appeared on metal
parts of the powerbook case when the adapter was plugged into the powerbook,
and this is the reason we feel the "joltage".  The third conductor (the tip)
was dead.  So, I only give the results from the two "live" conductors.

and I also measured, with the plug pulled out from the wall

d) DC resistance from any of the three conductors on the DC connector to
either prong of the AC connector.

RESULTS

1.  Modified Apple YoYos (Both YoYos measured about the same).

a) A half-wave rectified (negative only) sine wave, 60 Hz, with the negative
peak (the half-sine) hitting -75 volts and the positive peak (the
clipped-off positive peak) hitting +44 volts.

b) 55 volts AC

c) 40 microamperes AC

d) greater than 10 Megohms.

2.  Madsonline

a) full-sine wave, 60 Hz, with +100 V positive peak and -100 V negative
peak.

b) 81 volts AC

c) 40 microwamperes AC

d) greater than 10 Megohms