Heathkit SB-10 Series Troubleshooting Manual page 72

If the dial mechanism slips while tuning, it may be that the beveled pulley is not gripping
the metal ring sufficiently. To remedy this, loosen the nut on the front of the shaft slightly
and move the bushing and shaft down very slightly.
If the pulley on the end of the main tuning shaft is positioned to the front of the metal
ring, the dial will not move unless the main tuning shaft is pushed in slightly. On the
other hand, if the pulley is positioned behind the metal ring, the dial will only move when
the main tuning shaft is pulled forward slightly so that the pulley is pressing on the back
of the metal ring.
In either case, the pulley can be positioned correctly by removing the large knob on the
tuning shaft and loosening the nut enough so that the bushing can be moved up and
down. When this has been done, the bushing can be moved up enough to permit the
main tuning shaft to be moved in and out. While doing this, the pulley can be
repositioned on the metal ring. This has to be done by "feel" as it is not possible to see
when the pulley is correctly positioned. When the pulley is correctly positioned, the main
tuning shaft and bushing can be moved down enough to provide smooth operation of
the dial, the nut tightened and the knob replaced.
Note that it is not necessary to remove either the escutcheon or front panel to perform
this operation.
Figure 10. Main Tuning Shaft Beveled Pulley
Servicing Procedures Page 72