I had this same Issue with RobotLinking Full Graphic Smart Controller 12864. What I did is firs check with 470 ohm resistor as described above. It worked, but I decided to do the job as it should be - I unsold goldpin bar, then put there connector instead of soldering. Then experimentally set proper resistance with of the hidden pot. It worked VERY well :-) so thanks for advice !!!! I had idea toby glov - Controllers