Hi. I'd appreciate any help! I too have a repair issue with the SynScan dead hand controller. Here's what I think happened - after some visual observations and great polar alignment, I wanted move to EAA, so I wanted to control with my ASIAIR Pro via USB-B port into the hand controller, and fumbling in the dark, I probably inserted it into the RJ12 port. The outer metal shield of the USB-B plug probably shorted the connections in the RJ12 socket. The controller turned off, never to turn back on again. No smell of any burning, nothing. It shut down, and never started again.
Bottom line, I think I shorted some of the RJ12 pins and controller shut down, permanently.
I opened up the controller - and everything looks perfectly clear and clean. Any thoughts on which component could have gotten the damage and replacing it may recover the hand controller (especially because the hand controller costs $155+tax these days, and I would prefer a few dollars of component - soldering instead...).
Here are some pictures, that may help.
Oh, and this controller came from the SkyWatcher SynScan EQ5 Pro upgrade kit - even though it says 'Celestron' inside.