@janoc:
In the first video he's doing an MXM videocard, which is smaller than the bottom heater, so full bottom preheat. Even on that one it struggles but lift might've been ok.
The 2nd video uses a hot air heat gun as top heater,
not the
IR lamp. It's also in his comment:
"As most of you know, the T-862 is a pretty cheap machine on Ebay these days. The trouble is it won't get hot enough to do the bigger jobs so I decided to experiment. I took apart a heat gun and took the gubbings out of the T-862 so I had the best of both worlds!"
"With Ease"... If you see him pulling on that BGA with tweezers... Should come off like butter...
People in the past starting out with T862 or T870 (slightly larger preheater) using it for larger pcb's/bga's might've had few successes but too much fails switching to something more usable pretty quick.
"but at the very least it should be possible to desolder a knackered chip with it without destroying the board (if the chip doesn't survive you don't care as it was defective anyway)."
You've probably seen the "bullshit" video too?
Ok, there were, still might, BGAs that had/have internal defects, like 8xxx and 9xxx that had problems with bumps. nVidia made the wrong choice back then.
Many failing BGAs are fine and do only have a solder problem.
Prefer reballing over getting "new" chips. With a reball it's not a fake sanded/re-lasered re-printed whatever chip.
(If it's still the original on the pcb and not abused by oven, hot air, hair drayer, paint stripper, stove etc or DIY seen it on youtube attempts.)
If you can't buy new or used/recovered/refurbished BGAs, reballing is sometimes the only option to get it working again.