Power Supply Issue?

So a friend of mine recently got a "BROTHER INTERNATIONAL: Brother MFC 9440CN" the voltage req. says 120, yet the Voltage on the power supply for his computer is 115. Whenever the printer is used the computer powers off. So I think the power supply specifically the voltage is the issue. Is this the case or is there another possibility? Thanks for the help.

First of all 115 and 120 refer to the US standard for ac. In Europe and other places the standard wall outlet sees 220-240v there. Most supplies will see the 115/220 switch in order to switch when used in one place or another where the voltage is different for a wall outlet. That's all that is.

For seeing a system shutoff completely when a printer is plugged in suggests a defective printer seeing a direct electrical short to ground immediately sucking the current from the supply to ground. You are fortunate that it simply shut off and the system wasn't damaged as a result.

The supplies in something by Brother would be low quality and simply tossed in something tossed on retail store's shelves. If the printer was found to be good when tested on another machine then the supply simply wimped out when adding one more device and should be replaced being a likely defective one. One of the two is at fault.

sorry wrong post

It depends on whether or not it's connects by usb like most now do seeing a separate wall adapter or connects by way of serial/parallel port where a problem printer can even prevernt a system from starting up if found defective. The problem seems to point more at the supply being faulty where the slighest draw sees it shut off from a lack of regulation.

This is why trying the printer on another system will show if that has a defect of it's own. Both items should be tested since either or both might even be seeing defects. A bad printer somehow drawing on a faulty supply? bad mix! But you still need to rule one thing out to point to the other.

Thank you for the response. Well the computer/power supply has been tested already in that it had a printer being used before this new one and there has been no technical or power issues with it or the computer at all. The brother printer however says on the online description:
Power Consumption Operational 495 Watt
Voltage Required AC 120 V ( 50/60Hz )

Now the power supply the computer is using is 600w. This printer is an office printer: http://reviews.cnet.com/multifunction-devices/brother-mfc-9440cn/4505-3181_7-32571641.html do you think the amount of power it requires means he needs a much more powerful power supply, also I only brought up voltage since the power supply is 115 and 220 or 240 i think and not 120 and 200something. When you search for power supplies one with 120v instead of 110/115 are much more rare so i thought that might have something to do with it. thanks for correcting me on that.

Why are you not plugging the printer into the wall outlet???? Also what power supply are you using????

The only thing that plugs into the computer buy the specs. are the 10/100 Base-TX ethernet, Hi-Speed USB 2.0 and USB Direct Interface/PictBridge. The printer itself gets it power from the wall plug in.

Ive heard of usb printers bringing a system down due to a fault with the printer itself taxing the usb bus itself. That then pulls a weak supply down or simply causes boot up problems due to hardware detection problems.

A printer is always plugged into an ac source like a wall outlet or power surge protection strip not the supply on the system that provides 12vdc not 115-120v ac there as the highest voltage.

One way to see if the printer itself is seeing a fault while the supply there is suspect would be trying it on another system. If it prints normally elsewhere the supply is the problem simply failing to provide for the one more device added by way of the usb bus. That shows the supply lacks adequate regulation and is getting pulled down too quickly from the light draw that any usb device would see.

Yes the printer is plugged into the wall. It is connected to the computer through a USB connection. Sorry I should have specified that earlier it seems.

The thing now with the mention of having tested another printer on the same system without problem would generally suggest that the one in use not the system has an internal problem pulling on the usb bus. But that would cause a long delay in booting the system rather then seeing a total shutdown with a good supply in.

The system shutting down can also be caused by an entirely different problem like something overheating with the overheat protection circuit kicking in or even something most would miss a weak battery on the board if there's no bad caps on the board itself deciding to let go sometime. This is why trying the printer on a totally different system will show if that is seeing any problem or you still need to look for something else.