Zwo EAF not getting good focus and question?

The EAF has a flat side along the shank that connects via the coupling. Ensure that one of your grub screws is tightened to this flat surface to reduce slippage. It sounds like the grub screw on the coupling is likely slipping.

It could potentially be worth replacing the grub screws.

Loran Hughes:
My first thought would be to make sure the set screws in the coupler are tight. They can loosen up with use and cause the focuser to slip. 

CS,
Loran

Agree, I have had this happen after the initial setup, you will likely need to recheck this and your backlash setting as the first step.

double check the screws , flat curve mean ,focus  no moving ( stars size is the same after each step) , so check if zwo focucer is moving  or not ,if the answer is yes , them check the telescope focuser is moving too
if not , is the screws 

CS
Brian

I agree with Brian's suggestion. I had my EAF fail and that it was the EAF rather than the coupling could only really be diagnosed visually. I note the comment about updating the firmware - I didn't try that myself and perhaps I should have - maybe that would have saved me the cost of a new EAF.

I've experienced similar problems three times. the causes were:

1. The screws that mounted the EAF onto the scope focusing mechanism came loose and needed to be re-tightened.
2. Dirt in the helical focusing rack which was preventing the EAF from moving the focuser properly. Dismantled, cleaned, lubricated. All worked perfectly afterwards.
3. Like you, I have multiple EAFs. I had all my rigs dismantled for transport, and when I reassembled them, I accidentally put the EAF that had been on my Williams Optic ZenithStar61 on my Celestron EdgeHD9.25. The EdgeHD requires the autofocusing "max step" to be set to 200 otherwise the EAF doesn't move the focuser enough and I was getting a "flat" curve, with the EAF unable to find a focus point. I'm using ASIairs so I just had to go in and modify that configuration setting.

I hope this helps

Clear Skies,

Chris

Dan Kearl:
Thanks for all the helpful responses.
I put the EAF's back on and shot last night.  I used new screws to mount the EAF. The focus racks in and out like it should and settles and shoots but I still got flat curves and the stars were not great....Bat mask focus is much better.
I am pretty frustrated since they have worked well in the past. I guess it is possible that the EAF's have just gone bad which doesn't say much for ZWO products unfortunately.
I will take off and re-install and try them one more time the next clear night.

Do you mean focus racks in and out with the EAF installed? Or without it installed?

Also, what step size do you use for autofocus? What focal length is the imaging train? Perhaps the autofocus step size somehow got changed?

One troubleshoot I might suggest is manually focusing on an object in the distance during the day without the EAF installed. Then install the EAF, and take note of the focus position of the EAF after you've installed it (let's just say it's 10000, for example), then command the EAF to move to various manual focus positions (like 10100, 10200, 10500,11000, etc) and back to the original focus position, and watch to see if and how focus changes. If focus doesn't change, the EAF may be done for. If it does change, you can visualize how much each overall EAF step size impacts the focus change, and then you can adjust your autofocus step size accordingly and see if that helps the autofocus routine.

David Foust:
Do you mean focus racks in and out with the EAF installed? Or without it installed?

Also, what step size do you use for autofocus? What focal length is the imaging train? Perhaps the autofocus step size somehow got changed?

The focus racks in and out with the EAF installed and I am running the AF routine.
The focus knobs of course are frozen with the EAF installed and I install the EAF after I have set the focus with a Bat mask. I know almost exactly where the focus is on these 
scopes and install the EAF at the approximate correct focal length. For some reason they just are not working as they should.
I am using them on 600 and 700mm Askar refractors. 
It runs like it should except not getting proper focus.
I use the default EAF settings on the Asiair. 30 for the step setting, all others are default.
I have always used those and the EAF worked fine, not sure why they would change?

David Foust:
Got it, just wanted to make sure I understood correctly. So the focus motor works as it should, racking focus on and out, but the autofocus routine itself isn't achieving the correct focus. Perhaps the backlash of the EAF has changed as you've used it and needs updated to a new value? Maybe resetting the step size to a new value like 35 might reset the autofocus routine? Not sure, but worth a try!

I will try it, Thank you very much.