This happened to me once before.  You might check that the block
that slides back and forth inside the Tempo control box has not
been turned.  What happened to me was the rod was in a strange angle
to put the leather nut on, so I thought I turned the rod -- but
I also turned the block inside the box!

Duaine Hechler
Florissant, Missouri
http://www.hechlerpianoandorgan.com/