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I am currently setting up my EQDrive unitrack with my EQ 3-2 mount and upon opening the EQDrive config, I press read and stare into the abyss as I realize that I know nothing about the motor parameters and gear ratios.
I'd be greatly thankful if somebody could put me on the right track.
So my birthday just past so money to splash on astro stuff , i will have my 1000D modded by juan at cheapastrophotography and also have ordered an autofocuser from deepsky dad https://deepskydad.com/autofocuser i know they can be done DIY but this is a neat package and costs about the same as a SW autofocuser and a hitechastro focusmaster and i`m no electronic wizard and pavel seems to have a good product and works with ascom and confirmed it works with APT i will update in a few weeks time when hopefully i will have received and tried out .
Repairing a Tal MT3A Mount STEPPER MOTOR Help...
Before anyone says "why bother" let me just answer because I'm not ready to pick up a Losmandy at the moment...
So I have a Tal 200K which I have enjoyed quite a lot. I have always known that the single motor MT3A mount was less than ideal but it works and if nothing else, an 8" Russian made Kletsov catadioptric scope on a super solid peer mount is a pretty good conversation starter, and some of the views I've seen of Jupiter, especially with a 16mm Nagler - well they were amazing...
So a few months ago the mount stopped tracking and slewing at a star party. I could hear that the motor was spinning or making noise, but the mount was definitely not moving under the motor control. I might have just waited and bought something else, but I've had some major expenses plus I'm expecting another due to a large move about to take place so I can't justify spending the money at the moment, BUT I would really like to have a working mount for the Mars opposition in July. So I decided to tear it down and take a good look.
I was able to pull the mount casing apart ... and kept going, largely thanks to the PDF AndyH so kindly shared with me that had all the great teardown photos .. despite the native German which apparently translates into comical English with Google Translate ("Loosen the maggot whisk and the grub screws..." is that right??? )
The part that took me some time was realizng after removing the screws holding the case together and removing the setting circles and springs, that it was pretty difficult to unscrew the collar holding the drive shaft in the mount casing. For that I had to use a long screw placed into a hole in the collar as a kind of spoke to get some leverage to unscrew it. Once it started it was easy. Next I was more apprehensive about the drive shaft- The shaft fits through 2 bearings that had not seen freedom in 15 years, so I had to wack the shaft pretty darn hard from one end to break it free. I did this (again thanks to the photo in the pdf) using a block of wood over the end of the sharft - hitting the wood with a small hammer, and then a larger hammer. Like the collar once it was freed up it was easy to slide it through.
From there I just took stuff apart until I got into the drive gearbox. The small clock-like gear assembly was not difficult to remove and finally I got a good view of the stepper motor. At first I thought the gear was slipping on the shaft but it winds up being more serious. I removed the gear (loosened the 2 grub screws.. or were the maggot whisks?.. ;-) Of course I kept all the little screws in a secure place and tried to keep them attached to their mating parts when possible. But I think I'll be able to reassemble things..
I don't see any broken gears. My idea is to clean them up and lubricate them with a good quality lithium grease.
THE STEPPER MOTOR
I hooked up power and the controller and I clearly saw the drive gear is not slipping, but the motor is slipping, - internally. So I need to either repair the motor which no longer has the torque needed to drive the mechanism, or replace it. There's no way I can get the original motor (Tal is out of the astronomy biz and in Russia), and I don't know the specs about the motor to know how to ID it properly with an equivalent. It may be a type NEMA 17 with 6 leads. They aren't that expensive but will it fit? (looks pretty darn similar) Will the gear fit? Does it take the same signals/control voltages? etc. Alternatively Can the motor be repaired? I don't know much about stepper motors so I have non idea..
I know that stepper motors measure steps in degrees, and I imagine there's a spec that specifies the rate of spin, but I' don't know how to find this out for the motor in the MT3S. I have seen a NEMA 17 stepper motor in Amazon and it's less than $20, has 6 leads and has a 1.8 degree step. I might just take a chance and buy the motor and see if I can figure out the wiring.. if it's the same voltage...??...
I've attached an image of the printing on the motor and a short video showing it's unfortunate behavior.
If anyone has any suggestions how I can move forward I'd really appreciate it.