Thanks guys for pushing me to look harder - there indeed is another connection to the gate that I missed. It comes from the control board, but I haven't been able to track it down more specifically yet. It looks like it may come from the micro computer chip, so I may be in trouble. I haven't got up the gumption to ground the gate again for fear I'll burn out something, but I guess that's what I'll have to do.
Thanks again. I'll open this back up once I have more info and/or questions.
Doug