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Skysensor 2000 with vixen GP mount motors problem


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Hi all, first post so I trust I'm in the right place. I have tried other forums and everyone has been extremely helpful, unfortunately there may be no solution but here goes!

 

I've been using this set up for many years successfully but recently tripped over power cable that connects to a 1998 SS2KPC (running v 2.04) resulting in cable damage. This has now been repaired but now I can no longer power the motors on the mount when 'GOTO' is pressed and the 4 yellow direction keys will not move telescope despite red motor light showing on (pic2) These 4 buttons work perfectly with all other menus.  I have double checked the wiring by meter against diagrams on p114 of manual (pic 1) and repair is all correct and there is also 5v output into 8 pin plugs. Also all computer menus are available and all showing up correctly. All telescope configurations remain as they always have

 

I have also found that the unit memory cannot retain my location and time when turned off which I realise is an internal battery problem as it is registering just 0.08v rather than required 3.6v and another CN member has kindly posted on site instructions on how to replace. Would this affect motors though? I assume it is purely for memory.

 

I am nearly 100% positive the motors were not damaged and the two 8pin connecters show no sign of damage or being pulled out of motor sockets by the power cable accident so wondering why the motors are not getting the power. I know the set up is old but I'm very happy with it when it works and although parts are like hens teeth to find, if there is a solution or advice I would be greatly appreciative. I am I missing something really simple??

 

Many thanks.

 

Michael

Cloudy Manchester UK

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ss2k.jpg

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  • 3 months later...

Id be surprised at that- the drivers will have current control and chopper circuits managing that. 

My guess first is high resistance connection - you need 2 amps or so through those drive pins. Can you rig up a load resistor and meter to check for current ?

Have you an oscilloscope to look at the motor drive signal ?

 

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This is an old design, I wouldn't assume the drivers had short circuit protection.  I'd be interested to know what the driver IC's are.

It's also possible the encoders were damaged, resulting in an invalid input signal which the CPU doesn't recognise. 

Some idea of the cable damage would be useful. 

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40 minutes ago, nonlinear said:

This is an old design, I wouldn't assume the drivers had short circuit protection.  I'd be interested to know what the driver IC's are.

It's also possible the encoders were damaged, resulting in an invalid input signal which the CPU doesn't recognise. 

Some idea of the cable damage would be useful. 

The Skysensor 2000PC was pretty advanced for it's time. It has reverse polarity protection on the power input for example which not every has!

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I agree. I had one myself a while back and it is still my favourite system. Way better than the Sphinx starbook that replaced it. Electronics has moved on a lot in the last 30 or so years, and there is a big difference between putting a diode in the power line, and implementing comprehensive protection on the motor drivers. I'm not saying it's not there, I don't know, but I wouldn't assume is was either! :) We really need to know how the cable was damaged.

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  • 5 months later...

Hi all,

I replaced the battery and now the unit retains location data but still not working motors and no solution from Vixen or Bresser unless I can try the repaired cable with a known working unit although what you have said about potential damage being caused by the cable to someone elses unit that seems unlikely!

The original damage was several wires were pulled out of the cable end connected to the unit. See pic.

As I do not have the electronic knowledge to test any further than original post info. I think I will have to call it a day which is a pity as it was a great system.

Thanks for your input!

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  • 2 weeks later...

hi all

the skyscanner 2000 uses a TA7291P brushed full bridge driver, Toshiba website states it being protected. Could be a cracked solder joint on the PCB header connector (resolder them) or the little terminals could have been stressed (bent out of shape) too. Best get a correct end to end pinout table and check continuity from the PCB to the servo connections. Could also measure motor resistance and see if you get much the same at the PCB pins end with it all connected.

HTH Joe

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Thanks for posting the driver type, very interesting. Yes, the outputs are protected, but  the application notes make the following points:

  • Be careful when switching the input because rush current may occur. When switching, stop mode should be entered or current limitation resister R should be inserted. 
  • The IC functions cannot be guaranteed when turning power on of off. Before using the IC for application, check that there are no problems. 
  • Utmost care is necessary in the design of the output, VCC, VM, and GND lines since the IC may be destroyed by short-circuiting between outputs, air contamination faults, or faults due to improper grounding, or by short-circuiting between contiguous pins.

...all of which can happen if wires are pulled out of a connector when powered up. 

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Always difficult to capture all eventualities, so manufacturers always add caveats. Also difficult to ascertain failure modes without access to the HW layout and SW strategies. The driver has protection so it is probably fine. If the PCB designer followed the rules then it too is probably fine (say an undersized track blowing). Let's see if the cable works on another system, though I'd advise a pin to pin check between a good and a suspect cable first to make sure there is no chance it could damage a good system. 

Not to say the driver isn't damaged, just saying diagnose it in order of probabilities. 

Just to add, I've done ISO16750-2 testing as part of my job. 

HTH Joe

Edited by Bigfatflabbycat
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Many thanks to all of you who have contributed to this thread and especially to AndrewRrrrrr who checked out my cable and ss2k unit. The great news is the unit is still working well! The cable had been wrongly repaired and as Andrew rightly pointed out to me; "The diagram is misleading because people think that little bit sticking out in the middle underneath is the tab for the locator block, but it's not!! The diagram is looking at the pins on the ss2k unit itself, not the connector block and it's "right way up".

I'll post again when the cable is fixed ..... which should be some time before these Manchester skies ever clear.

 

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  • 1 month later...

Hi Mickb53

New Member, first time post.

I've just dug out my scope & Skysensor and used for the first time in almost 5 years at the weekend, only to find that the Date & Location settings (& User preference Set Up) is no longer being stored. Have identified the issue with internal battery lifetime, as you mentioned, but wondering how easy this is to replace? I've never used a soldering iron in my life and the guidance on line seems intimidating!

Don't want to give up on it as it's still a great piece of kit and I'll always remember the scrimping and saving I had to do over 6 months to buy the kit. I've never been able to look at a Pot Noodle since...

Thanks in advance

Rob

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  • 4 weeks later...

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