I recently purchased a new computer for my business. It is a Systemax SYX-1113 operating on Windows 7. I operate three small CNC controlled machines with it. The machine input is via serial cable which I have connected to the computer with USB to serial adapters. I have operated these machines in the same configuration with older pc's that had far less power than this one without any issues but this one keeps dropping the usb connection. The computer is plugged into a 15amp circuit that has nothing else operating on it other than the monitor and speaker system. I have checked and tested the circuit for wiring issues, circuit breaker issues and power draw which have shown no problems with the circuit. The problem begins when I use a small paper shredder connected to the same a/c circuit. I can hear the usb connection drop by the familiar usb disconnect sound and the connection to one or more machines is lost when the shredder is operating. When I unplug each of the usb adapters from the computer I get another disconnect sound and then plug them back in. The connection is restored and I can communicate with the machines once again. There is not a single adapter that fails or a single usb port. I have tried every combination of usb ports available on the computer with the same results. No other devices fail that I can tell such as keyboard, mouse or printer. They all appear to remain connected unless they are re-setting themselves. A couple of days ago I added a small refrigerator to the circuit and now it appears that when the fridge compressor kicks in the usb connections drop as with the shredder. Do I have a problem with the computer power supply that will not deliver enough power for the usb ports or could there be a loose connection or board? The specifications show that is has a "550 watt Bronze Power Supply". As I stated before, I have had the same CNC machines connected with the same usb-serial adapters as well as two dongle security keys, keyboard, mouse and printer connected to other less powerful computers and never had any issues like this. Am I asking too much from the usb power supply or something? It has twelve 2.0 ports and two 3.0 ports available which I have tried all of them with the same results. I am using seven ports to include two for the dongle keys which I can't imagine would draw any noticeable power. I am not a computer genius so if this is something simple that is easily solved someone please let me know how to do it. If not I guess I'll have to have a little talksee with the salesman that sold it to me.