OK, this has happened to me twice now - first with the DEC motor; most recent with the RA motor...
The beginning of a session; turn on the mount; go to the align process; DEC axis motor doesn't run - crickets. No sound whatsoever on that motor. Cycle the mount power - no change - RA motor runs as expected the DEC is silent. Take off the motor board housing - inspect - nothing looks awry. Re-seat internal connectors - no change. After an hour of retrying these steps -no change. Pack it in for the evening take the mount off the observatory pier to troubleshoot at home. Two days later, get the mount ready to troubleshoot, ....And... the mount motors work perfectly!!
With nothing more to do on troubleshooting, take the mount back to the observatory. It works flawlessly for several months and many sessions.
Last session out, the RA motor does the same thing - crickets - while the DEC motor runs as expected. Follow the same steps as before but no joy. I even check the motor board fuses - they all read intact. Take the mount home to trouble shoot . This time I try trouble shooting the next day (about 18 hours after the initial failure and again about 22 hours) - the failure persists - the RA motor is silent; the DEC motor runs fine. I even tried resetting to the factory defaults - no change. I get a good nights sleep. Next morning (about 40 hours after this last failure) I gather some troubleshooting tools (meter, clip leads, etc). I power up the mount prior to begin trouble shooting, ...And... the mount motors work perfectly!!!
I have mixed feelings of relief and frustration. I haven't taken it back to the observatory yet, but I expect the motors will run fine.
I have had this AVX since 2014 and it has been my secondary (small refractor) astrophotography work horse setup since then - working pretty much flawlessly. So I got to thinking about "what has changed" during this summer when these two problems occurred? I have used this mount connected to the same computer. The mount gets commands from SGP and PHD2 as well as a planetarium program (first The Sky, now Stellarium). Here is what has changed:
1. I updated the Celestron mount ASCOM driver for the mount before the first failure. This is the update that fixes the SGP centering accuracy (includes time offsets for goto from a single direction). This was a pretty mild update. I don't expect this is the cause.
2. I did start recently checking all my connections to my laptop (camera, FW, guide camera, focuser, and mount) in daylight prior to the evening session just as a pre-check. For both failures, I inadvertently left the PC connected to the HC RS232 port when I powered down the mount. The three PC apps were still connected to the mount at mount power down and stayed that way for an hour or so (while the apps were presumably pinging for a connection or issuing commands to an un-powered RS232 port on the mount's HC). I know RS232 ports are notorious for sneak path powering of internal circuitry. I can't tell if that is happening here or if the mount HC and/or MC firmware are responding in an unintended manor to this condition.
I suspect item number two above is the root cause - but it is unproven. It could be that some internal Firmware feature is setting some timeout that persists at power cycle. That timeout being somewhere between 22 and 40 hours). The problem is that I can try to repeat and confirm this mode, but it shuts me down for something between 22-40 hrs.
1. Has anyone else experienced similar failure and then miraculous recoveries?
2. I would love to prove root cause, but I am not willing to try to re-create an undesired operational mode that is unaffected by power cycling (or anything else I tried). Does anyone know if there is an internal reset pad or jumper that sets a "pristine" condition for the next power up (so I don't have to wait 22-40 hours to run again)? Does anyone know if I pull the lithium coin battery for a sufficient period if this creates a "pristine" condition that allows me to restore motor operation at next power up?
Helpful information: HC firmware 5.21.2336; MC firmware 6.07