On Tue, 4 Dec 2007 09:11:37 -0800 (PST),
wrote:

Hi John

I thought I had all I needed but now I have one last embarrassing
question to ask...

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Don't be embarrassed. You knew you didn't know and asked for help.
That's commendable.
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Should the 5V ground be connected to the 70V ground? I.e should the
5V gnd be connected to the mosfet source?

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Yes.
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What is the reason for it to be attached not attached?

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The source is common to both the 70V supply and the supply providing
the signal the PIC will send to the gate, so their grounds both have
to be connected to the source.


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JF