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Help with non working C8 Byers Clock drive?

Beginner Celestron Equipment SCT
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#1 fjparks


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Posted 19 February 2021 - 02:35 PM

Hi All,

Hopefully someone can get me going in the right direction. I'm experienced in electronics but brand new to astronomy. I have my Dad's old Celestron Super C8 Plus or more likely it is a Powerstar 8. (Has both manuals but it is DC powered). The drive is not working (no LED illumination on the hand unit and the drive does not move). I have no battery pack, only a 12V plug-in for a cigarette lighter which is not a perfect fit into the hand unit's 12v receptacle. The cigarette lighter adaptor plug / jack is conventionally wired with "+" on the center pin. (I have seen in posts that the 12V jack might be wired opposite and that a voltage regulator could be blown out). Does anyone have any advice, schematic, or documentation that they could point me to?

Pics attached.



Attached Thumbnails

  • Base M.JPG
  • Hand Unit M.JPG



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Posted 19 February 2021 - 04:10 PM

  I have repaired a number of telescope electronics but unfortunately  not that exact one but there are two common causes I have found on  these type units. One is that someone  reversed the polarity and that causes damage to ICs inside the hand controller. Many times the controller is using TTL logic which runs on 5 volts and there is 5 volt, voltage regulator to drop the 12 down to 5. The ones they use are not reverse polarity protected so it gets fried.  So  check  if one is present and the output is 5 volts. If not I would recommend replacing with a good old LM7805 and adding protection diode.

   The other common problem is the multi-pin connector. The wires will  break at the solder joint. 


                     - Dave 

#3 telesonic


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Posted 20 February 2021 - 03:43 AM

Your scope base is a Powerstar - and yes, it is DC powered.


The DC plug for this should be (tip/center pin negative) for the base, and also the same goes for the handbox. I've ran mine on 12v DC from a jump box, and it worked fine - so I don't think voltage would matter, provided you have the proper adapter and correct polarity.


First thing I would do - make sure your (power) plug is wired center negative, from there...

check to make sure that someone hasn't swapped or re-soldered the jacks in the handbox and base, thus changing polarity. I don't recall the wire colors off the top of my head, but that would be one other thing to check as well.



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