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replacing a damaged cable on orion autoguider

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#1 pushrod

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Posted 26 March 2020 - 09:33 PM

Hi , as the title says I want to replace a damaged  cable between my orion autoguider and my EQ5 mount - the ST4 one. Can I just use a 6 core RJ12 connector of suitable length or do I have to buy a dedicated "ST4 guider cable" which looks identical to RJ12 connectors but is more than twice the price! Thanks



#2 Jim Waters

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Posted 26 March 2020 - 09:39 PM

Can I just use a 6 core RJ12 connector of suitable length 

Yes - but make sure the wires (colors) are not reversed.  I make my own.

 

You can also buy them from OPT Corp.


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#3 pushrod

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Posted 27 March 2020 - 05:13 AM

Yes - but make sure the wires (colors) are not reversed. 

Thanks Jim, but not quite sure what you mean - surely the colours are irrelevant on a connecting cable as as long as A goes to A' ; B goes to B' ; C goes to C' etc etc as RJ 12 connectors can only fit in one way?

 

………. or do you sometimes get cables where the first core does not run to the first position in the 2nd connector  etc ???

 

On a slightly different note PHD is constantly suggesting among other things that my ST4 cable could be damaged. When I check the 6 cores they all have continuity, five of them with less than 1 ohm , and one which has a resistance of just over 2 ohms - does anyone think it likely that this is significant and could be the reason for the error messages or should I expect to look elsewhere. Obviously I will swap out the cable, but just wanting a heads up if it is likely to be something else. Thank you. 



#4 Pauls72

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Posted 27 March 2020 - 08:17 AM

Most camera/mount combinations use a straight through ST-4 cable. There are a few combinations that require a crossover cable. All you can do is look at the documentation for your guide camera and mount. If you get it wrong, it doesn't hurt anything. With the wrong cable the mount will drive the wrong direction or not at all in some directions.

 

 

ST4-PinOut6.jpg


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#5 rgsalinger

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Posted 27 March 2020 - 08:36 AM

Why bother? You can guide through the USB/Serial cable that connects your mount to your computer. Much easier and one less cable to snag, break, forget to bring etc.

Rgrds-Ross


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#6 pushrod

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Posted 27 March 2020 - 10:20 AM

Most camera/mount combinations use a straight through ST-4 cable. There are a few combinations that require a crossover cable. All you can do is look at the documentation for your guide camera and mount. If you get it wrong, it doesn't hurt anything. With the wrong cable the mount will drive the wrong direction or not at all in some directions.

 

 

attachicon.gifST4-PinOut6.jpg

I tested the cores of the cable and they all showed continuity (to varying extents) from one connector to its corresponding position and the diagram you posted, if I understand it correctly, seems to indicate that I need a straight through cable so i'll go ahead and get one and hope it solves my problem. Thank you.



#7 elmiko

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Posted 27 March 2020 - 10:33 AM

I agree with Ross, don't bother with the cable.pulse guide using Eqmod or similar.

What mount are you using?


Edited by elmiko, 27 March 2020 - 10:34 AM.


#8 Alex McConahay

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Posted 27 March 2020 - 11:07 AM

Pay attention to Pauls72's advice (Post 4). There is no "Standard" in the St-4 Standard.  

 

I would add, though when he says:

 

>>>>>>>All you can do is look at the documentation for your guide camera and mount.

 

An even easier method is to simply match whatever you have in your existing cable. Just look through the clear plastic RJ connectors on the existing, where you can see the different color cables, and match the colors on each end. 

 

Of course, the better situation is to consider direct mount guiding with PulseGuide or whatever. 

 

And, beware, if you did a continuity check and each individual wire was working, then the cable as a whole should be working. It may be something else. It is, after all, just a dumb wire.

Alex



#9 rgsalinger

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Posted 27 March 2020 - 12:31 PM

Or, if you must keep using that cable, contact Orion and get a replacement.  Can't be very expensive. Then there is no possibility of a mistake. 

Rgrds-Ross



#10 TelescopeGreg

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Posted 27 March 2020 - 02:17 PM

To what Alex said, it's just wires.  Continuity should be sufficient.  BUT, continuity should be zero ohms, not "a couple", and not varying.  If it is, then you have a bad connection, and that will prevent it from working reliably.

 

You can probably find an equivalent cable, but while you have the cable sort of working, write down what the pin connections are.  When you get a replacement, make sure that the same pins are connected in the same place BEFORE plugging it in.



#11 Pauls72

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Posted 27 March 2020 - 03:02 PM

ShoeString Astronomy sells straight through ST4 cables. He will build you the cross over version if requested.

http://www.store.sho...products_gp.htm

 

 

 

 

ST4-Examples.jpg


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