I know this is an old post, but I just got the same error (mechanical error 1500) after a head crash on the material (last time I let it run over night). Now the s50-670 just sits on the error screen. As tgrinds explained the pressure roller position sensor etc. does anyone have an idea of how to check this and what it actually looks like? Before I put the cash out to have a service tech (more importantly get the printer back up and running as it's in the middle of a very large job)...
Chaz
Edit: Somehow I got lucky and the error went away. I had restarted the printer several times and kept getting the error. Left the printer on for 15-20 min and let it sit.. then turned off and on again and it went through the initialization and into the ink circulation and to the ready screen... no more error. checked the encoder strip to make sure it was still nice and straight (which it was) and moved onto a test print. Print came out nice and clean and nothing out of whack. Hopefully this may help if someone else gets this error.