what u have done so far is correct..error 502 is a carrier stall error..u have to make sure that encoder strip is on the guide slot and u have to reseat as well the ink carts just to make sure they are properly loaded on the printer.anyway, about your concern if there's a pic..i was able to google the chassis of a940 printer but it's not that clear.it only shows the cart carrier.

well this error that u got .. looks like there is a problem with encoder strip.here.. try this site.from here you can see screenshots of your a940 printer.

here are the steps::

 

open support.dell.com > Troubleshooting and FAQS > under Search for Solutions field, type in error 502 then click GO > then select > highlight the radio button for **  There is an Error 502 - Carrier Stall displayed on the panel. then push Next  and from there you can follow again the steps and you can as well see figures about your a940 printer... hoping this will help you resolve the error in a timely manner.. :smileywink:

 

and by the way, if still the problem persist.. i would suggest that you'll get in touch with Dell tech support right away. please take note as well of the Journal that flashes on the right hand side of your screen.that might help for them to resolve your problem quickly.. :smileyhappy:

Thanks! I appreciate the help- 

No probs!! :smileywink:

I have an A960 DELL all-in-one, and have been experiencing the same error code 0502.  I have troubleshot with a DELL Tech, and again thru my printer help.  Is this a common problem with the Dell All in One Printer?