One of my biggest complaints about my Harbor Freight blast cabinet is that the media delivery was poor at best. The cabinet comes with a tube that you're supposed to fix to the bottom of the cabinet so it was buried in the blast media. The problem was the gun would not create enough vacuum to pull the media up the hose so it could enter the airstream and blast your work piece.
I searched YouTube and found a bunch of videos showing how to improve the media delivery. It was very easy to do and took about an hour using materials I already had around the shop.
At the lowest point in the media tray I drilled a 5/16 hole and brazed in a short length of tubing. About an inch down stream I drilled a 1/4 inch hole and brazed a short length of tubing onto it. I ran a 1/4 inch hose up the side of the cabinet and run it thru the body of the cabinet. This vents the 5/16 tubing.
I then ran a new length of 5/16 hose up thru the floor of the cabinet and re-attached it to the spray gun handle where it is supposed to attach.
Venting the media feed tube this way allows the pick up hose to flows a ton more air thus delivering the media to the gun. It works great now.
I've noticed that this new set up increased the static electricity charge and I'm experiencing more static shocks than before. I added a ground wire with an alligator clip on one end to attach to my work piece and ran it thru the cabinet wall and attached it to the conduit on the shop wall. No more shocks as long as I remember to attach the alligator clip to the work piece.