Troubleshooting the AS GT Mount
Submitted: Monday, 5th March 2007 by Narayan Mukkavilli
What to do when your Celestron AS CG5 Mount doesn’t power up
I have owned and operated a Celestron Advanced Series CG 5 with GoTo mount for the last couple of years and have used it many times at home and also at my dark site without any problem.
Recently, when I set up one Friday night and connected to my usual battery pack nothing happened…no power to mount-the red light didn't come on, and the hand controller stayed dead.
The mount was just two weeks out of warranty. I contacted Celestron Tech Support on the Internet, and was given a ticket number. I also contacted the dealer the next morning, who promised to get back to me the following Monday-and I am yet to hear back from him. I learnt later on that Celestron Tech Support can take up to 4 weeks to get back to you as they are considerably backed up. I was on my own-but thanks to the internet- not alone.
I posted my problem on Cloudy Nights and also the Celestron AS Series Yahoo Group and received a number of helpful suggestions. Since these suggestions may be useful to others who own a Celestron CG5 mount I thought to organise and document these in case anyone else runs into the same problem I did. This particular issue is not covered in the otherwise excellent FAQs over at the Yahoo group, so this problem-and the associated solution must more recent in origin.,
I’d particularly like to acknowledge input from Rod Mollise and Ken Hutchinson over at the Celestron Yahoo group upon which the following is largely based.
Step by Step Troubleshooting
0. Is the LED working
Right next to the power switch on the mount is a red LED. It is connected directly across the power leads after the switch and LEDs generally last a very long time. If that LED comes on but the rest of the mount does not work you might have a serious internal problem. In such an event there may not be much one can do –unless you have serious knowledge of electronics. (luckily for me this was not the case)-and what to do in such an event is outside the scope of this note.
In my case the red LED did not come on and there was no power to the hand controller. In such a situation I’d suggest the following step by step approach:
1. Double check the battery/and or power source.
Bad batteries and inadequate AC power supplies cause more problems than anything else.
2. Check the fuse in the power cord
The cigarette lighter plug that is at one end of the 12 V power cord supplied by Celestron has a 3 amp fuse. The fuse is easily accessible by unscrewing the tip. Warning-do not do this in the dark, the tip itself has two small parts and there is a spring behind the fuse which can pop out and would be a monster to find in grass in darkness. You can visually check the fuse, but a circuit tester is best.
(in my case the fuse was fine. However the fact that this fuse exists at all makes me wonder whether I should not have a similar fuse in my 12 V AC adapter (non Celestron) power supply-and by way of abundant caution I think I will run the mount off battery rather than AC power in future.)
3. Check the power cord itself
Unlikely but still needing to be checked is whether the cord itself is "open" somewhere along the line. Again, take your circuit checker and test that you have 12volt at the plug-end that inserts into the mount.
(I didn’t have a problem here)
4. Check the centre pin in the power connector in the mount
The centre pin in the power connector on the mount looks like one piece at a casual glance but it is actually two pieces. If you put the tip of a fine Stanley knife blade between the two halves and gently spread them apart a little you can usually fix any contact problems with this connector.
(As simple as that. 30 seconds, once you know what to do-this fixed my problem!)
5. Check the switch
Now it starts getting trickier, and I wouldn’t advise doing any of the following while the Mount is still under warranty.
The power switch is known to fail. In fact, I remember when Phil Harrington reviewed this mount for Astronomy magazine some years ago, he picked this as a potential weak spot and recommended that it be left on all the time as it appeared so flimsy. (I haven’t so far, but am going to follow this advice from now on!)
Apparently some people have been able to get going by moving the switch on and off until it starts working again, but even if this works once or twice I’d suggest it’s a symptom of a deeper problem that may resurface at the worst and most inconvenient time.
A first approach to solving this problem is to try cleaning the switch contacts with some zero residue cleaner,
If this fails then you have to consider either replace it or just solder a jumper across its terminals to keep it always on. See this thread on Cloudy Nights for a picture of how someone has done something similar
As I said luckily for me I didn’t have to open up the mount to access the innards, so I don’t have first had experience with step 5.
Hope this helps someone, sometime!