DK3 declination control defective

[freiform]

Hi forum, 

the declination control of my DK3 hand controller appears to be broken. The motors themselves are working fine, so does the control for RA-axis. The symptoms are depending on the speed set:

- 1x, motor turns in the same direction for DEC+ and DEC-

- 2x, appears to work

- 32x, DEC+ works, DEK- turns very slowly (1x or 2x?)

Can anyone provide some help? On fist glance it appears a switch might be broken. Or could it be the drivers themselves? Unfortunately, all ICs have a coating, so I do not know the exact types - presumably to prevent reverse engineering and/or repair.

Any ideas or comments? Are there schematics available for this controller? 

Thanks

Sven