I've been asked to test a MYDMX3.0 dongle as there is no ouput from it. It's installed correctly in device driver and hardware manager sees it and reports the serial number so I'm happy that side of things are working correctly but patching a light into the software produces no output. I've put together a simple two LED XLR tester but there's no LED activity either. I do have the DMX output LED flickering away on the dongle as well as the LCD showing Pc.
As it's well out of warranty I've removed the PCB from the case, disconnected the XLR board and checked the 5 pin output connector on the main PCB. What I am seeing is continuity between pin 7 of the MAX485 IC (DMX-) and ground and I suspect that that aint right. Before I contemplate replacing a SM IC can someone confirm the DMX- line shouldn' t be grounded or is this perfectly normal and I need to look elsewhere?