"One thing to try is reversing the polarity."

I'll try the polarity thing, as far as the wallwart goes it works fine
with my second 707.
I bought it and the connector from allelectronics.com, so both are the
same 2.1mm, and it has all the specs for 707/727 power.

I also read about cleaning the contacts with isopropal, I'll try that
as well.

It would be nice to get it up and running.

Thanks again for all the input.

Ed