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Schematic for DD2 (DMD-2?) Hand Controller?

Accessories Beginner Cassegrain Celestron DIY Equipment
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#1 fjparks


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Posted 22 February 2021 - 07:31 PM

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). 

The hand controller is a DD2 (DMD-2?)

It is center pin negative and has been reverse polarity connected to 12V.

I fixed this, but still have no illumination of the power LED and no drive motor movement.  
The is a diode in series on the 12V input (presumably for reverse polarity protection) and it tests good, as does the 8V LDO regulator.
Any chance someone has a schematic for the PCB?


Attached Thumbnails

  • Hand Unit M.JPG
  • Base M.JPG

#2 photoracer18



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Posted 22 February 2021 - 07:43 PM

If there is no light on a Vixen type controller from the early days its most likely looking for the opposite polarity. Of course you could still be having some electronic issues leftover. And I am not sure that Celestron might have converted all those controllers they made for the C8s to +12v. And that controller is not a DMD or a DD as it has different parts and controls from the Vixen controller. I am betting if you plug +12v into it the light will go on., assuming its not dead. Did you replace the diode using the same orientation as the dead one? You know that toggle switch on the top there is the on/off switch, correct?

Edited by photoracer18, 22 February 2021 - 07:44 PM.

#3 telesonic


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Posted Yesterday, 05:51 PM



Before you get digging too far into your controller, here are a few things that come to my mind: (now that you have the correct center-negative power adapter)


1) I do see some rust on the screws on yours - check to make sure that all electrical contacts are clean. On the 12v jack and also the 8 pin DIN jack/plug. Perhaps there is corrosion.

2) These can be powered 2 ways, if I remember.  A) you can plug the power supply into the handset or B) you can plug the power supply into the 12v jack on the drive base. IIRC it should work either way. Keep in mind though, the 12v jack on the base may have been rewired to center positive at some point - verify that it hasn't been changed first.


3) I'm not certain on this - but the map/lamp switch may need to be turned on to power it up, it's been a few years since I used mine so I don't remember exactly. Try that, and see if your LED illuminates. In the following link I provided - that does seem to be the case on some of these. (It's a few pages in) Photoracer also mentioned this above.... so give this a shot first, if you do. If your lamp does not illuminate, it may be possible that it was fried from reverse polarity, but still test the drive for movement. If so, easy fix.


Also, the drive on this is reaaly slow, and pretty quiet. Mark your housing and RA circle with a pencil - then let it run pluggged in for an hour or so, it will have moved a bit.


I don't know if you have came across this thread yet or not, but it may be of help:




Hope you get yours working, they are very cool old drive setups. I still have mine, and could probably answer any questions regarding the 12v socket wiring on the base if needed.



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