The other problem old color tv's had with convergence circuitry
was lots of interaction between the other pots and coils.If you
have not already tried this,you should unplug the convergence assy.
(some tv's like rca's need to have a jumper installed to ground
the cathode of the vert. output tube for the set to work without
convergence board)So check the schematic first to see what has to be
done.With the dynamic convergence removed you can now set
the static convergence without having interference from the
dynamic circuitry.you can then set all the controls and slugs
to their mid position and reconnect the convergence board.
Make sure to turn the power off before reconnecting.You may
not even need to disconnect the board,just setting everything
to midrange and then starting over may solve the problem.
Maybe this will solve your problem.You may get some needed
range on the controls that had no effect previously.I would try
that first and then check the resistance on the pots and coils.
If everything checks ok and you still have the problem,I would
look at subbing some new diodes in place of the selenium to see
if that fixes it.
Regards,
Swanson