Marlin won't connect - what up?

[andywalter 7]

Hi,

I have a UM delivered 26 March, has version 1.5.6 motherboard and Arduino 2560. This has been running fine using whatever original firmware it came with, and RepV version 0026, connecting to Windows 7 Professional on COM6.

Recently my son has "upgraded" it to Marlin or somesuch, and tried using Cura 12.11 .

The machine is now pretty much junk - using Cura we can "Expert" -> Install default Marlin firmware"

and it tells us "Installed firmware: ultimaker_250000.hex" OK. This has junked the machine - it cannot connect, the "Print" dialog tries all the baud rates and fails to connect. But just what IS this "default firmware" ? Is there a .hex file somewhere? If so, what and where?

Using Cura 12.11 to upload other versions of firmware from

http://http://firmware.ultimaker.com/firmware/

sometimes partially works - with some Cura connects, the X & Y axes work, it can build my shape for about 10 minutes and then suddenly locks up, and I have to use Task Manager to kill the build.

I'm getting desperate - right now I'd be happy to recert to RepG 0024, if only I knew the original firmware file.

Can someone please advise us what's going on here? E.g. there's no README fil in the //firmware folder to tell you what's meant to work with what machine & what software; frequently I've seen Cura & RepG whinge about not being able to find som .xml file at start-up - does this matter?

Advice please - my machine's a real mess and I'm getting very frustrated right now trying tons of stuff that doesn't work. I really want to see something simple to use - why should I have to attempt some custom-build and muck around somewhere with my extruder settings? My extruder has the "Newbolt.jpg" type knurled-bolt, it's the lower of the 2 images on

http://http://wiki.ultimaker.com/Marlin ... _Ultimaker

page. My machine is standard - please can I have a simple file to upload to the firmware, and please can I know what version of Cura is stable and won't lock-up after 10 minutes running. My PC is fast, a core I7 with 6GB ram, USB2 ports, and was rock-solid with original Arduino code & RepG Ver 0024. I want it rock solid again please.

Thx,

Andy