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Meade LXD75 - Cat Got the AR-5

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#1 SJMarty

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Posted 09 November 2019 - 07:10 AM

Hello!

 

I have a Meade LXD75 AR-5.  I leave it set up by one of the windows that my cats like to sit in.  Apparently, they like to do things other than just sit in the window as I discovered yesterday that the declination cable has been bitten through in several locations.  I found this thread and the pictures are very informative but unfortunately, his solution was crimping a new connector.  I know this mount has been out of production for a while and I've done some searches for the cable without much luck.  Can anyone recommend a source for a replacement cable?  If not, other suggestions welcome.

 

Thank you,

 

-Steve



#2 SkipW

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Posted 09 November 2019 - 12:25 PM

My daughter had a cat that would chew up cords too. Many cellphone charging cords, not to mention rolls of TP, fell victim to that beast.

 

Anyway... what does your declination cable look like? What I can find online looks like it may be a coiled cable with an RJ45 (8-position) modular connector (same size and shape as the connectors on an Ethernet cable) on each end. Is that right? If so, hold the two connectors side-by side, tab side toward you and both cables cable downward, like this:

 

IMG_7902crop.jpg

 

Look carefully at the order of the wires in the two ends. They are probably either in the same order or opposite order (the illustration is a Celestron 6-position Declination motor cable; it has the wires in the same order: white on left (position 1), blue on right (position 6), and all others the same at both ends). If yours is an 8-position modular connector with wires in identical or exact opposite order, then a suitable replacement might be one of these:

 

https://www.digikey....=1&pageSize=250

 

Note the "Style" column at far right. "Standard" style has a given color connected to opposite pins at the two ends (i.e. 1 to 8, 2 to 7, etc.) and "Reverse" style has a given color connected to the same pins (1 to 1, 2 to 2, ..., 8 to 8). The photo shows a "Reverse" style cable.

 

The length in the listing is the extended length; retracted length will be about half the extended length. The shortest DigiKey has in stock are 5 feet, manufactured by CNC Tech: P/N 1175-2403-ND (Standard) and 1175-2451-ND (Reverse). Look at the datasheets and verify that the P1 and P2 wiring matches yours you want if you want one of those.

 

Before using any replacement, compare the wiring order against the original! If they're at all different, bad things are very likely to happen!


Edited by SkipW, 09 November 2019 - 12:28 PM.


#3 SJMarty

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Posted 10 November 2019 - 05:58 PM

The dec cable on an LXD75 mount is an RJ45 on one end - the end that plugs into the control panel - the other end is wired directly to the dec motor board.  These images from the other thread I mentioned explain it a little better...

 

post-213744-0-91887500-1513795927.jpg

 

post-213744-0-27341400-1513809069.jpg

 

post-213744-0-52151600-1513809012.jpg

 

I opened the motor housing up and didn't pull hard but just a little and that connector doesn't budge.  So at this point, I'm not sure if the thing is soldered to the board or not.  The OP in the other thread mentioned a couple of times that he thought the connector was soldered on but since his problem ended up being the RJ45 connector (on the other end), I'm not sure if that was ever confirmed.



#4 rferrante

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Posted 11 November 2019 - 07:45 PM

It does look soldered on. If it were plugged into a header (and therefore removable), you'd be able to see the base of a header in your photo. It looks like there are male crimp terminals in the white housing, the pins go through holes in the PCB, and are soldered on the bottom.

 

This is a better method of attachment than simply soldering the wires onto the board, as the housing, and the crimp at the insulation, gives some strain relief. But it is just as permanent :-)

 

--Rob



#5 SkipW

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Posted 11 November 2019 - 08:24 PM

Oh, yes, now I remember... I was going to look at that other thread but didn't right away. Then I forgot to actually look at it before posting a little while later.

 

That looks like a Molex connector. If so, it should come off. Can you slip something like a jeweler's screwdriver between the connector and board and gently(!) try to pry it away from the board?

 

 



#6 MikeBY

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Posted 12 November 2019 - 02:57 AM

That connector does look different.  Looking at the closeups, there does appear to be solder on the molex inserts. What is not clear is if someone soldered the wires to the insert after crimping but before inserting into the shell or if they attempted to solder the insert to the pins coming from the circuit board. Normally, Molex connector male pins are in a plastic header that fits flush against the circuit board, and then the pins are soldered on the back, like you see at JP1. Often times this may include a key or a latch to lock the female connector and insure that it's oriented correctly. In this case, there doesn't appear to be a plastic header, which by itself doesn't mean much. It could be there is a clearance issue, or it was not originally designed to connect to wiring using a single female Molex connector.

From the neatness of the connector shell and wires, I suspect that the wires were crimped, then very carefully soldered to the inserts before insertion into the connector shell. Attempting to solder the insert to the male pins with the shell already in place would likely result in cold solder joints as it would be impossible to heat the pin and the insert sufficiently and flow solder into a joint without damaging the plastic shell, much less verify the quality of the joint.  If the problem turned out to be the other end of the cable and is solved, I think it's best to leave it alone. Inserts are made of spring steel and are not meant for soldering per se. If you continue to have connection problems and you are having problems pulling off this connector, then a small screwdriver between the shell and circuit board might help loosen it up. You can then clean and burnish the pins and inserts in place, or if necessary, replace it entirely if there is enough slack in the wiring to accommodate the shortened cable.

 

Michael


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#7 SkipW

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Posted 12 November 2019 - 03:08 PM

The problem with replacing these cables terminated in small connectors is that crimping the necessary terminals to the wires is about the only way to make a replacement, and the crimping tools are muy expensive! If that is a Molex 2 mm connector block, as a practical matter, the terminals cannot successfully be crimped on without the specific crimper (don't ask me how I know this), and that tool costs hundreds of dollars.The extraction tool also costs more than $30. 

 

If a connector block that works happens to use Molex 50212 or 59354-series terminals, I have the right crimper and extraction tool (and a scad of unused 50212 terminals) from another project; I'd be happy to crimp terminals on a cable for the cost of parts and shipping plus a small contribution to help offset the cost of the tools, but that may be a long shot at this point.



#8 SJMarty

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Posted 12 November 2019 - 03:36 PM

I had another thought that I'd been talking to someone via PM about.  Since it's clear at this point that the connectors are soldered on and my issue is literally in the middle of the cable, instead of trying to get the existing connector off, I was considering cutting the cable and terminating the ends in an surface mount RJ-45 box that I would secure to the outside of the dec motor housing.  Something like this...

 

https://www.amazon.com/dp/B005E2Y9WY

 

I could then just have a cable with RJ45 plugs on each end that would be easily detachable (preventing further feline feasting).

 

I'm just afraid I'm going to damage the dec board trying to get the existing connector off.  Concerns or potential issues with this approach?



#9 SkipW

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Posted 12 November 2019 - 08:16 PM

I don't understand why someone would solder a connector like that, but what do I know?

 

That said, this might be the most practical solution. I gather that you would terminate the wires from the existing connector at a punch-down block inside the new box, then use a patch cable with RJ45s on each end. The main risk I see is muffing the cable order in the punch down, or using a Standard patch cable when you wanted Reverse or vice-versa. Still, if you're careful, and check the order (twice, maybe with "a second set of eyes" reviewing your work!) before going live, it should work!

 

Good luck, and please let us know your progress!



#10 MikeBY

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Posted 12 November 2019 - 08:23 PM

I had another thought that I'd been talking to someone via PM about.  Since it's clear at this point that the connectors are soldered on and my issue is literally in the middle of the cable, instead of trying to get the existing connector off, I was considering cutting the cable and terminating the ends in an surface mount RJ-45 box that I would secure to the outside of the dec motor housing.  Something like this...

 

https://www.amazon.com/dp/B005E2Y9WY

 

I could then just have a cable with RJ45 plugs on each end that would be easily detachable (preventing further feline feasting).

 

I'm just afraid I'm going to damage the dec board trying to get the existing connector off.  Concerns or potential issues with this approach?

That certainly will make repairs from the next kitty feast easier !! :)


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