TOP ADVICE
Do not put too many coins onto the spinning wheel. This will cause churning and nothing will come out.
Take the cover off where the knobs are and try to get an understanding of how it works.
There are two levers. One near the left belt and one near the right belt. Lift the left lever and you will see the rails that the coins travel on as they cross the reject hole. Move the DIAMETER knob and you will see how this part of the machine works.
Next you will see a lever near the belt on the right. If you pull this lever to the right and HOLD it, you can wiggle the metal plate that the knob is attached to and remove the whole plate. It can be hard to remove, so just continue to wiggle it to you get it off. You may need to remove this to clean trash or a nasty jam. You have to pull the lever to the right and HOLD it to get it to go back on.
Jams are going to happen. You can try hitting the stop button. This causes it to reverse a partial turn and sometimes clears the jam.
Another option is to stop the machine and turn the DIAMETER knob to a larger setting. This opens the rails and will cause the coin to fall in the reject cup where you want it. You can turn the machine on for a second or two to see if it will eject. You don't want to leave it on long because the reject cup fills FAST.
Next step is to turn the machine off, and ALSO turn the THICKNESS knob to a large setting. If the coin has gunk on it it needs to be able to fit under the plate.Turn the machine on for a sec or two and hopefully the coin will pass under the plate and into the reject cup.
Once the problem coin is cleared, return the knobs back to the original settings. If the THICKNESS knob wont turn back, you have coins stacked under the plate. This is another reason to not overload the wheel. I try to reach in and pull them out if I can. If I can't I take the cover off and remove the plate and fix the problem.
These are good machines and list for over $1000 on any online business site.
If you luck up and find a Scan Coin 313, BUY IT. It has a large hopper that holds 4000 coins and has an auto feeder. This keeps the right amount of coin on the spinning wheel.
I have both and used both to pre-run the $900 in loose pennies I got this week. The 303 ran about $400 in the time it took the 313 to do $500.
The 313 retails for $1500 +
There are faster machines out there, but I challenge any $250 to out perform it.