SGH-T989 (UVLDH firmware) Goes into Recovery mode, but not Download I'm trying to get my SGH-T989 into Download mode so I can flash TWRP with heimdal. It's been awhile since I've done this and from what I recall (and have researched a bit) I need to:


unplug cable
power off
hold Vol_Down + Vol_UP 
plug in cable


This isn't working though. All I get is recovery mode and what I want is Download mode. 

Not sure if the device/cable/PC is bad. Using Linux. Tried a 14.04 box and a 16.04. What have I missed?. Been googling, but lots of mixed info. Anyone help?
Thanks

----- update ----------
Older Samsung devices might require a special USB dongle/jig like this one to trigger Odin mode - just plug it in when the device is powered off. It's essentially a resistor between USB pins so you can also make one yourself if you're up for it.