Skywatcher Autofocuser Advice

[FenSkies]

I'm hoping someone can advise. I bought the Skywatcher variable speed autofocuser (really just a focus motor) a couple of years ago. It worked perfectly with my EV90 for several months, but then I got an 8" Dob and didn't use the refractor for a year.

Coming to use the EV90 again, the motor struggled to turn the focus spindle. I have tired several fresh batteries, taken all the tension out of the rack and pinion short of making it sloppy, and still the motor struggles. It runs in both directions when removed from the scope.

Does anyone know the cable connections between the motor and control box, and whether it is a stepper motor or DC? If it's a stepper then I'm hoping that the connection to one phase has come adrift.

Any advice or thoughts welcome.

[Tomatobro]

from your description it seems like you have the DC version. Between the motor and the output shaft there is a gearbox which has a high reduction ratio so with the motor removed from the focuser with just the output shaft with the flat on it its not possible to stop this shaft from rotating with your fingers when powered from the handset.

If you can stop it turning then the  problem lies with the motor controller and most likely the controller.

Later on I will do some tests where I will attach a pointer to the shaft and give some idea of the revolutions per 20 seconds at max and min so you can compare.

The numbers are (Max speed) 4 rotations in 45 seconds and 2 rotations in 55 seconds at minimum speed. 

Using a blutak pointer on the end of the shaft

Edited May 29, 2023 by Tomatobro
photo added

[FenSkies]

1 hour ago, Tomatobro said:

from your description it seems like you have the DC version. Between the motor and the output shaft there is a gearbox which has a high reduction ratio so with the motor removed from the focuser with just the output shaft with the flat on it its not possible to stop this shaft from rotating with your fingers when powered from the handset.

Yep, that's the one I have. Identical to the photograph. Unfortunately I am able to stop the motor with my fingers, so it's not looking like a simple bad connection or cable problem. Time to take a closer look at the PCB methinks. There is a possibility that I damaged something when changing the battery, which is a very tight fit. I'm keeping my fingers crossed that it is something fixable.

Thanks for the info on the expected turn rate too. Very much appreciated. I'll report back when I've either fixed or killed it.

[SteveNickolls]

Thanks for posting I hope you are able to resolve the issue you are having. I've had the same unit for focusing my StarTravel 102 for a number of years now and while basic does the job fine. When you get the unit back working you might check this replacement controller unit and wi-fi unit to replacec the stock SW brand item.

https://www.firstlightoptics.com/skywatcher-focusers/4tronix-focusrf-remote-control-for-dc-focus-motors.html

It actually has an on/off switch and a better build, no more removing battery between uses. The wi-fi unit allows control over a greater distance if that brings more to the table.

Hope you get the problem fixed.

Regards,

Steve

[FenSkies]

6 hours ago, SteveNickolls said:

Thanks for posting I hope you are able to resolve the issue you are having. I've had the same unit for focusing my StarTravel 102 for a number of years now and while basic does the job fine. When you get the unit back working you might check this replacement controller unit and wi-fi unit to replacec the stock SW brand item.

https://www.firstlightoptics.com/skywatcher-focusers/4tronix-focusrf-remote-control-for-dc-focus-motors.html

It actually has an on/off switch and a better build, no more removing battery between uses. The wi-fi unit allows control over a greater distance if that brings more to the table.

Hope you get the problem fixed.

Regards,

Steve

I've just taken a look on the FLO website. Looks like an excellent solution if, as is probable, I can't fix my unit 🙂