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Original Nexstar 8 computer/control problem?

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#1 lowlacs

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Posted 25 November 2012 - 11:16 AM

Hello everyone, a few months ago the telescope fairy blessed me with a great deal on an original Nexstar8. Since then this has been my favorite and most used scope. We were blessed with beautiful skies on thanksgiving and the following night this year and this scope performed flawlessly as it has since I purchased it a few months ago. I happened to be up late last night and decided I would give Jupiter a shot with the webcam but to my suprize the scope did not agree.
So, heres the situation, the best I(rookie) can describe it and the pleade for help from the Gurus(you).
When powered on the red back light shines but I have no "nexstar ready" or prompts to start allingment. I can press info and the lcd will read "23h.59.9m" along with the up/down arrows, press down key, then "0.0degrees" then down again, -25.6. Also, The enter button will allow the date and time to be set, but then nothing. The rate button will also allow to set to any speed selection but the scope will not move when I push any directional buttons.
I have always ran the scope on batteries so I wouldnt think a power spike is possible and I dont recall any low voltage issues either. I now have it on a 12volt power supply inside to test. I know this is an old scope but I am hoping not to have to explain the cost of new mount to the wife.lol
Heres the ? Has anyone here ever experience the issues Im having and is there a fix or any advise really? I relly did like this scope and mount the motors where very quiet and Im prayin its not dead, Please help the rookie!
Thanks for any replies. :question:

#2 Tel

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Posted 25 November 2012 - 12:47 PM

Hi Lowlacs,

This is a tricky one because the "try this, try that" options are somewhat limited where the Nexstar 8 is concerned.

At this time and as far as superficial testing is concened therefore, can you confirm:

1) You are getting the same effect/result when your 'scope is connected to your 12V external power supply. (?)

2) What does this supply represent, (i.e. external 12V battery or 12V AC/DC transformer)?

3) With the assumption that the 'scope HAS been working on a set of 8 internal AA batteries, nevertheless, is the cord, running from the external supply to the mount, a snug fit, particularly at the mount's jack plug point ? (Have you tried wiggling it while looking at the hand controller screen) ?

4) Being an old 'scope, you might check for corrosion/verdigre at the point at which the hand controller plugs into the mount, (in the arm of the mount), and clean the HC's connection.

If none of this brings the hand controller "to life" then it would seem that deeper investigation into the base of the mount will be necessary, looking primarily for any loose connection(s).

Hope this helps and indeed fixes the problem. Please keep us all posted.

Best regards,
Tel

#3 Midnight Dan

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Posted 25 November 2012 - 02:46 PM

Hi lowlacs:

If, after trying Tel's good advice, nothing works, it may be the handset has given up the ghost. If you know someone else with a Nexstar, even a newer one, I believe the handset should still work with your older mount (Tel, do you know if this is true?) and you could try a swap.

If you determine it's the handset, at least a new handset is a lot less than a new scope.

-Dan

#4 Tel

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Posted 25 November 2012 - 03:32 PM

Hi Dan,

I really don't know for sure, but I see no reason why a more modern HC shouldn't work.

We both know that the Nexstar and Nexstar "i" HC's are not upgradable as are those of the later SE models, but certainly the SE HCs, (Versions 4+), work in the older "i" series ! (I have one for my ol' "i") !

Best regards,
Tel

#5 lowlacs

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Posted 25 November 2012 - 04:50 PM

Thanks for the input guys. After heavy research I found some script about the hc being picky about low temps and that some handcontrols come to life after a coulpe hrs, so I left the scope be with the power on for most of the day to no aveil. So after reading Tels advise I thought Id take a closer look and maybe inside. I also found that after many, many presses of the directional buttons the scope would sometimes move and sometimes run-off with no stopping it outside of killing the power. As this would happen the red backlight would dim which I thought confirmed some of Tels ideas. So after a quick trip to tool shed for my handydandy multimeter sure enough it had a serious voltage drop when the motors did decided to run and sometimes dropped to 4-5volts. I reluctently opened the power input and switch cover to jiggle the wires and look for corrosion. Unfortunatly I didnt see the problem but Im positive its a connection problem as the scope seems to work fine after reassembly. So in conclusion the Old Scope LIVES! I cant say that the problem is fixed but atleast I know now my scope isnt dead and I dont have to replace my mount or control as of today, and I tell ya that brings a heavy sigh of relief.*

To answer all of ur ?s I am currently using a small ac/dc power converter to power the scope and yes I had found a few other nexstar owners fairly close by that were more than happy to lend a hc for test purposes. I gotta say the folks in this hobby sure are alot more helpful than some of the motorcycle guys I once delt with,lol. For this I thank u all.*

So just one more question guys, Do u believe in the whole cold natured hc? I will obviously be testin this theory as the scope will now return to its home in my scope shed with all its friends later tonight, but I just thought Id ask u guys opinion on this thought. Thanks again Tel and Dan for ur valued input. Joseph in Florida.

#6 Tel

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Posted 25 November 2012 - 05:41 PM

Hi Joseph,

Let's hope that it's a connection problem and that a terminal clean may solve the problem. It certainly sounds as if it might.

As to the low temperature effect on the hand controller's screen, this is a common nuisance: the screen appears alive but little if anything in terms of instruction can been seen.

I believe that there is a heated "sleeve" available for the HC in the US (no doubt your countrymen will direct to its source better than I'm able to do from here in England): but alternatively, a simple, chemical hand warmer, "rubber banded" to the back of the unit should make the screen legible at all times throughout any observing session.

Hoping this helps,
Best regards,
Tel

#7 Midnight Dan

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Posted 25 November 2012 - 08:27 PM

Hi Joseph:

Not sure what you mean by "cold natured", but as Tel mentioned the display becomes sluggish and hard to read in cold temps - a common problem with LCD displays. Other than that, it should work fine. If you find that the cold causes you problems with the display, you can rubber-band a chemical hand warmer on the back of it during a session. Or, you can purchase a heated case for it here:
http://store.smartas...miiforceco.html

Hopefully, plugging the connectors out/in has solved the problem. Over time, oxides build up on the metal surface of connector contacts and interfere with the connection. Just plugging/unplugging a connector several times will rub through the oxide layer and improve the connection.

-Dan

#8 thecrustychicken

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Posted 26 November 2012 - 11:01 AM

I believe that the old nexstar 8's (non I or GPS) have a different servo controller than the I's and GPS models. I'm not sure that the newer hand controllers are compatible with the originals servo controller.

#9 Bob Griffiths

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Posted 27 November 2012 - 07:44 PM

The original NS5's and 8's will NOT function with the newer hand controllers...

The 5i and 8i will...BUT not the original 5 or 8

Original firmware in the early NS5 and 8's had very poor tracking ability..Celestron completely rewrote the firmware and motor controls...

Bob G.






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