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I think I've found the answer to this after a bit of inspection - but I'll leave it to a bright Saturday morning to try and adjust this.
First confirm the degree of the error - I lightly pushed the end of the OTA with it powered down and their is a 2-3mm movement at the end of the OTA in the dec axis - RA is beautiful. Secondly DEC adjustments take time on slow speed - RA are instanteous. Third on PHD I have watched it calibrating where it clears DEC backlash - this sometimes takes 70 * 500ms pulses!
So my conclusion is this was poorly adjusted on arrival.
The good news is it seems a quality finish that is all metal and once dissassembled - ready to adjust. The process would appear to be:
1. Remove the DEC casing to expose the motors and gears
2. Remove the motor by unscrewing 3 metal bolts
3. Using an Allen key slightly loosen 4 metal blots that attach the worm to the case, be careful loosening the 4 bolts that are adjacent to the brass 60 tooth wheel - ensuring you don't slip and damage this gear
4. There are two bolts that control the distance of the DEC worm to the main DEC gear - assuming these are parallel already - tighten each of these very carefully and slowly - turning the same amount on each to bring the worm slightly closer to the gear - after each adjustment (maybe only 2-3 mm movement at the end of the Allen key) stop and try and move the OTA to see if there is still excessive slop between the worm and the main DEC gear.
5. Once you think its right - tighten the 4 bolts holding the worm firm and do a final tension test - slow small steps are crucial in steps 4 and 5.
6. Re-attach the DEC motor and check their is some play but very little between the two 60 teeth gears (the key thing is to avoid sticking).
7. Tighten and lock the 4 bolts holding the DEC motor - do a final tension test
8. Replace the DEC housing - pray - switch it on and cross fingers - run it through a complete revolution of the worm in both directions at a slow - medium speed first - then a high speed test lastly
Tricky but do-able - does that seem right to folk here?
Matt
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