No Response ErrorsPlease read this entire article before you start troubleshooting. You may also want to read the article Internal Communications of Celestron Computerized Telescope Mounts before you start. This error indicates that the hand control is unable to communicate with another system component, for example, 16 and 17 are the motor control processors located inside the mount. 176 is the GPS module on scopes with this option. 178 is the Real Time Clock (RTC) module on scopes with an RTC. All Models Many times the problem is the connector that the hand control plugs in to. Try connecting the hand control to one of the AUX jacks (for mounts with an AUX jack), rather than the normal hand control jack. Also, the pins on the jack or the plug can accumulate slight amounts of corrosion that can interrupt the low voltage signals. These can be easily cleaned with contact cleaner available at electronics parts stores. Do not over do it, you do not want excess cleaner to short out the electrical connections. Be sure the power is off and use a cotton swab dampened with contact cleaner to rub any contaminants from the connectors. Also, take a good look at the pins and insure they are not bent or misaligned. Another potential problem area is that the plastic RJ-12 connector (phone-type connector) on the end of the coiled cable might need to be re-crimped or replaced. Or, occasionally the connection of the coiled cable inside the hand control has worked loose and causes No Response errors. This can be fixed by carefully removing the back of the hand control (6 screws hold it on) and reseating the connector. Occasionally one of the modules connected either to the AUX ports or the internal communication bus (the AUX bus) is bad and is flooding the communication bus with garbage thus preventing the hand control from communicating. For example, this has been seen with the internal GPS module on a CPC scope. Opening the base and disconnecting the GPS module allowed the hand control to communicate with the motor control in the mount and by manually entering date and time, the scope was again operational. Bad external modules like an external GPS unit, a SkyPortal WiFi module or a StarSense camera could also cause this type problem - test by disconnecting everything except for the hand control and power (the minimum required to use the scope). On rare occasions, the motor control may be stuck in "boot mode". Fixing the problem requires you reload the latest motor control firmware - follow these instructions. NexStar Evolution Series NexStar GPS Series The newest versions of the hand control - version 4 or higher - require motor control firmware version 4 or higher. If you have older motor control firmware, the hand control will display the no response error. See this article for details on GPS firmware versions and upgrading when necessary. Advanced Series with GoTo (AS-GT) Internal Connections - All Models NexStar GPS Series If you still experience problems, there may be a connector loose under the panel on the base of the scope. Using a 9/64 inch or 3.5mm hex wrench, remove the five bolts on the top of the base panel. In a well-lit space, slowly raise the panel, being careful not to pull any of the cables loose. With the panel raised about 2 inches (rolled-up socks are a good way to prop it up), reseat all connector cables you can easily reach. Reseat the panel and secure the five bolts. NexStar 5i/8i/8i Special Edition and NexStar SE Series NexStar GT, NexStar SLT, Astro Fi, SkyProdigy Series All Other Models
If none of these suggestions helps, it is time to try replacing hand control, circuit boards or cable assembles. Or it is time to call Celestron.
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