[Farmall] H Ignition issue

[genscan tds.net]

I have a really nice H that runs great with one exception.  I will be
working it in the field, and suddenly it will kill, just like you pushed in
the ignition switch.  It will not start again until it sits for an hour or
so, then it fires right up and runs fine again.  It has done this for the
last couple of years.  I believe it is an electrical issue rather than a
fuel issue, as  it stops so abruptly, and choking it has no effect.
     Are there any theories out there as to what the problem could be?