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LX 90 not recognizing LNT

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#1 dogeddie

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Posted 21 December 2019 - 06:22 PM

I have an older 8" LX 90 that I haven't used for a year or so. It was working fine when I put it away. I started it today and noticed the time was off, so I changed the CR2032 battery in the LNT module. Problem is, the scope doesn't see that the LNT is there at all. It will not self level or find north, and there is no calibrate sensors option in the menu, presumably because the scope doesn't recognize there is an LNT. Setup goes right to asking me to put the scope in the Home position - it should go to Auto Align and self level at that time. I cleaned all the connections, but no luck. Anyone help please? Thanks


Edited by dogeddie, 21 December 2019 - 08:37 PM.


#2 OzAndrewJ

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Posted 21 December 2019 - 08:17 PM

Gday dogeddie

Funnily enough, i had a similar problem a few days ago

The LNT should detect, even without the battery ( as that just keeps the time correct )

I also cleaned the contacts but it was only after inserting a few times that it detected.

I suspect it was just oxidisation on the contact wires inside the Aux socket

and a few insertions and wriggles cleaned it up.

Also, the unit must be plugged in when you boot, you cant hot plug it later.

 

Andrew Johansen Melbourne Australia



#3 dogeddie

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Posted 21 December 2019 - 08:39 PM

Andrew,

Thanks. I'll try it a few more times. I stored the scope attached to the tripod, pointed vertically with the LNT plugged in and a cover over it, so there wasn't a strain on the cord.



#4 dogeddie

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Posted 21 December 2019 - 10:15 PM

Took it out tonight and it isn't working. The little red fiber optic lights up for the red dot, but the time doesn't hold. The date does stay correct though. Had to set it up manually, which isn't too terrible, but I always like the ease of setup with the LNT



#5 OzAndrewJ

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Posted 21 December 2019 - 11:30 PM

Gday Dogeddie

Not sure what you mean here

Does the LNT show up in the menus now, but time is wrong????

The last date used is always stored ready for the next boot, but the time defaults to 8:00PM

thus it may "appear" to remember date.

Andrew Johansen Melbourne Australia



#6 dogeddie

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Posted 22 December 2019 - 11:41 AM

Andrew,

here is the progression when I turn it on:

 

1) Welcome to Autostar

2) Press 0 to align or MODE for menu

3) So I press 0

4) Enter date - it is there from last time

5) Enter time - says 8:00 every time

6) Daylight savings time - No

7) Then it says Alt Az Align - put scope in Home position, etc. Then it goes to 1st chosen star

 

I also plugged the LNT into the other Aux socket but with same results. Took the LNT all apart and sprayed with contact cleaner. Can't figure out what's wrong. Wish I had something else to plug into Aux socket to test that and at least see if the socket is ok.


Edited by dogeddie, 22 December 2019 - 12:14 PM.


#7 OzAndrewJ

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Posted 22 December 2019 - 03:27 PM

Gday Dogeddie

Certainly sounds like the LNT isnt responding.

The only way to properly test whats going on is to use a logic analyser

to see if the Aux bus is working

( Thats what i was doing a few days ago, when i found mine didnt work for a few starts  )

 

Andrew Johansen Melbourne Australia



#8 dogeddie

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Posted 22 December 2019 - 05:16 PM

Definitely don't have one of those undecided.gif



#9 dogeddie

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Posted 26 December 2019 - 05:40 PM

If I wanted to try to find somewhere to test the male and female ends of this connection, what is the name of this type of connection, or how do I refer to it in an electrical/electronic sense?



#10 dogeddie

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Posted 01 January 2020 - 04:26 PM

Does Meade make a plug in LNT to swap out with this one if it proves out to be bad?



#11 OzAndrewJ

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Posted 01 January 2020 - 06:04 PM

Gday dogeddie

Meade had plugin LNTs and ones built into the PE mounts

If you can only find a PE type unit, you can still wire it up

with an RJ connector so it plugs into a std Aux port.

 

Andrew Johansen Melbourne Australia



#12 dogeddie

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Posted 02 January 2020 - 05:44 PM

Thanks Andrew. So Meade does not make a compatible modern substitute?



#13 OzAndrewJ

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Posted 02 January 2020 - 06:29 PM

Gday dogeddie

I have no idea what Meade make re this anymore ( I suspect its discontinued )

but you can normally buy units secondhand or old stock off ebay etc

 

Andrew Johansen Melbourne Australia


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#14 dogeddie

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Posted 02 January 2020 - 09:58 PM

Thanks. I'm going to an Electronics repair shop tomorrow to hopefully get it tested



#15 EdIII

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Posted 03 January 2020 - 06:54 AM

Thanks Andrew. So Meade does not make a compatible modern substitute?

 

Andrew is correct. Meade is not making the LNT. Telescope Warehouse comes up with new ones some how. He also puts them on EBay. The ones I bought from him plug into the aux port and work just fine if you don’t mind the cable. With significant modification they can be wired direct. I think I paid $50.

 

Ed



#16 dogeddie

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Posted 03 January 2020 - 11:58 PM

Thanks for the tip, Ed!


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#17 Piet Le Roux

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Posted 04 January 2020 - 09:38 AM

From what I have read the LNT were a bit of a gimmick and the beginning of the Light switch idea. If you want to setup your LX90  to be accurate get the OTA level with a spirit level in all directions and then do a two star alignment. A while back I had problems with a  brand new Meade APM Dongle (it came out of a Meade box) that I wanted to use for guiding : The LX90 could not detect it. At the time I used patched firmware Ver. A1F7 and when Meade released new firmware A4S4 I tested it on my Audiostar. When I plugged the  dongle in the Audiostar detected it! StarGPS have now released a patch for the A4S4 firmwhere, which I am using now, and with that I dont have any problems. So what firmware are on your Audiostar?  



#18 dogeddie

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Posted 07 January 2020 - 08:44 PM

I brought it in to an electronics repair shop. He determined the cord for the LNT was bad. So we fixed the cord short, and I expected success - but it still doesn't work. I'm thinking that I will replace it (the LNT). Just seems so odd that it was working fine before I covered it for a year or so and left it unused.



#19 OzAndrewJ

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Posted 07 January 2020 - 09:43 PM

Gday dogeddie

Dont know how he determined the cord was bad.

To do it properly requires a logic analyser to see what comms are being sent on the Aux port

and i am pretty sure the tech would have no idea of how Meade does this.

 

Andrew Johansen Melbourne Australia



#20 dogeddie

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Posted 07 January 2020 - 11:23 PM

I think he was just detecting a signal from one end of each wire in the LNT cord to the other end for continuity. We couldn't do much else. It seems like it must be a problem in the module rather than within the aux ports on the scope because neither of the 2 aux ports work. You would think 1 of the 2 would. Do you think it pays to just try a replacement and see? I can get one for $40 shipped.



#21 OzAndrewJ

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Posted 08 January 2020 - 01:17 AM

Gday dogeddie

 

neither of the 2 aux ports work.

You dont know that yet, and technically, both Aux ports are identical and are wired in parallel.

You really need to see if the mount is trying to communicate via the Aux port first

If it isnt, then the problem is in the mount, and a different unit wont help.

If the Aux port shows communications are being attempted, then the problem is in the LNT.

Again, to see this, you need something that can sniff whats going on.

It cant hurt ( other than $40 ) to try another unit, but if you can check the Aux port first

it would be best.

Andrew Johansen Melbourne Australia



#22 dogeddie

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Posted 08 January 2020 - 09:35 AM

Thanks Andrew. I've been unable to find a way to check the aux ports. The repair shop said he could, but would need to get behind the port to access the wires, which looks like removing the panel on the arm. I'm not crazy about trying to pull off that panel, it looks like the whole tube would have to be removed from the mount. Is there another way? I can't find anyone with a logic analyzer.



#23 OzAndrewJ

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Posted 08 January 2020 - 03:15 PM

Gday dogeddie

 

You can remove the panel without removing the OTA, but you do need to remove

the wormwheel to get to some of the screws

That said, an RJ connector with pigtails on it is all that is reqd.

There are 2 Aux ports so plug the LNT into one and the RJ into the other

That way the RJ plug can tap into the Aux bus and see whats going on.

 

Andrew Johansen Melbourne Australia



#24 dogeddie

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Posted 08 January 2020 - 04:32 PM

Thanks again Andrew!



#25 dogeddie

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Posted 08 January 2020 - 05:39 PM

Andrew - Sorry I'm so thick. But if we use the RF connector with pigtails to test the ports, are you saying I would not need to remove the side panel?




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