The launcher will error out with this error if it detects any of the following:

A keyboard is connected to the computer

The dongle is not present

A sound card is not plugged in

There's a strangely placed ground connector in the cabinet which, if not connected properly could lead to amplifier buzz.

This ground point is supposed to be connected to one of the screws on the back of the computer. If it is disconnected in your machine then secure it under the screw on the top right hand corner of the back of the EZ2DJ PC. This should solve any buzzing issues

Many machines have had their pedals incorrectly removed which has caused physical damage to the wooden mount on the machine for the pedals as a result.

To avoid this from happening and correctly remove the pedals, unscrew the metal panel on the front of the pedal (not the metal plate on the pedal itself but the L shaped piece of metal at the front). Lift it away and remove the 2 Phillips head screws behind the pane before disconnecting the pedal switch. You can now safely remove the pedal from the machine.

Most of the original EZ2AC amplifiers have issues with the volume knobs (no sound at all, crackling sound, volume turning up or down by itself or not stable)

In this case, most likely you have to replace the volume potentiometers,here are the closest components i could find in order to replace the original ones (which are impossible to find):

- this one for the woofers/bass channel

- this one for the top/side speakers channel

Since the aforementioned parts 'shaft is too short, and it won't come out of the amplifier body and the body armor has the wrong shape which doesn't fit with the amp PCB, i bought this other potentiometer just to take out the shaft and the body armor from it and transplant it on the ones mentioned above which have the right resistance value. (The pinout of the replacement parts perfectly match the originals)

this is the part which we're taking the shaft and the armor body from

You'll also need to carefully bend the potentiometer's legs 90 degrees to match them with the holes in the amp PCB and the metal armor body legs 180 degrees in order for them to align. (In order to disassemble to potentiometers you need to lift the tabs of the armor body on the back)