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Newby's question about NexStar 80GT

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#1 Renie

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Posted 27 December 2012 - 08:12 PM

I am such a newby that this used 80GT is the first telescope I've ever touched! The first time I tried, the hand control powered up and I went through the alignnment process. The second time, it would not power up -- dark screen. I am using the battery pack and have tested it -- it is generating power but obviously the motor is not getting the power. Does anyone have the wiring diagrams for the circuits inside the motor arm? I'd like to try to fix this myself -- I don't have the money to buy a new one. Thanks!

#2 *skyguy*

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Posted 28 December 2012 - 03:08 AM

The power connector on the external battery pack cord might have become too loose to make a good power connection inside the power socket in the base. This has happened in the past to my GT mount.

Try spreading the two halves of the pin in the middle of the power socket on the scope's base. Be careful not to bend it too far or you may break one of the pins. Also be careful not to turn it as you may break the solder connection on the inside of the mount. You'll now have a tight connection which will ... hopefully ... restore power to your mount. Good Luck ...

#3 Tel

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Posted 28 December 2012 - 04:28 AM

Hi Renie,

A very warm welcome to CN and to this Nexstar forum ! :bow: :bow:

Additional to the sound advice given by "Skyguy", don't forget also to check the cleanliness of the "'phone connection" of the hand controller to mount.

In a relatively old 'scope such as this, there may be some corrosion or verdigris build-up at this point which might be giving rise to poor contact and thus loss of a hand controller power-up. :idea:

Best regards,
Tel

#4 Renie

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Posted 28 December 2012 - 10:49 AM

Thank you for both of your replies -- I opened up the motor arm and tested the inside of the connection where the battery pack plugs in and it shows that the two wires are being powered. So I thought it must be a connection further inside -- one of the other circuits or one of the wires between the circuits? Just not sure what each of them should look like or which wires should be live. I'll keep working on it. Of course, I can still use the optics but it would be much more fun to have the motorized part working.

#5 CelestronDaddy

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Posted 28 December 2012 - 11:00 AM

Renie - Welcome :grin: You might be able to get some help from the Celestron website or with their tech support. I've talked with them before and they were very helpful. They might be able to help you troubleshoot the circuit. Keep us posted and welcome! Tony

#6 Tel

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Posted 28 December 2012 - 11:10 AM

Hi Renie,

The pin connection and the wire extending therefrom may well be live when connected to the power source, but is power (consistently) reaching the hand controller socket ?

In other words, are you sure there is no corrosion etc. providing for an intermittent connection between the HC ('phone) socket and the feedline to the HC ?

Just a shot in the dark but in light of the fact that the HC initially powered up and then failed at the second attempt ....... :idea:

Best regards,
Tel

#7 Geo.

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Posted 30 December 2012 - 02:43 PM

Off the top of my head, the hand control gets its power at the coaxial jack not off the motor control board. I have parts for these and can walk you through any repair replacement you may need. Here's some pix of the motor control board cabling.

Attached Files



#8 Renie

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Posted 31 December 2012 - 02:41 PM

George, thank you so much for the photos. I'm going to ask my boyfriend to look them over and compare them to the inside of the motor arm -- I'll be back in touch as soon as he tells me what questions to ask!






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