Two days ago, I used an improper power supply on my 12 years old CG-5. So, whenever I turn on the mount, enter time, date, and then press for alignment, the mount immediately starts slewing in RA in its greatest of speeds. Theory says most probably the mount control board got damaged; and you cannot buy a spare one from Celestron, since they have been discontinued.
Yesterday, I decided to at least check what would happen with the correct power supply, and by pure chance I discovered a quick fix. Here it goes:
When you turn on your mount, before anything else, before aligning, or entering any sort of time and date data, before anything, you adjust the slew speed to "8" or "9", and then you press the RA motion button just once, as much as is necessary to create motion. Then, you perform a "quick align" (to be honest, I rarely use anything other than quick align), and the mount works!
Well, not everything goes smoothly after that; for example, I ordered the mount to slew to Vega, and it started searching it in the opposite direction, to the west. But until I decide if it is worth to spend money on a repair effort, or buy a new mount, I can keep on doing basic work.
Hope this will help others with similar issues.