PC Reboots after Printing

Desktop PC reboots unexpectedly after laser printer prints. 

Even though my PC is protected with a UPS (battery backup), and the laser printer is not plugged into the same surge protector/UPS, print jobs were still causing my computer to reboot. This is because the laser is on the same circuit as the PC and in my house, this is unavoidable.

Laser printers are power-hungry, demanding around 450 watts.  As I have joked in the past, when I print, the house-lights dim and the power company rejoices. 

Resolutions:

Past experience shows a new battery in the UPS fixes the problem (see this keyliner article: UPS Battery Replacement, and this article:  UPS makes clicking sound when printing).  However, this time, this was not enough.  The PC continued to reboot.

The next likely solution is the PC's power supply.  Power supplies weaken with age and unexplained power problems can point this direction.  My machine is an older Dell XPS desktop tower, and it has been running 24-hours-a-day for the past 5 years.  It has, what was then, a powerful ATX 480-watt power supply.


Stopping at a local Best Buy electronics store, I picked up a 600-watt power-supply for $30.  Replacing is relatively easy, taking about 10-minutes, but you do have to be comfortable opening a PC's carcass and unplugging a lot of wires.  If you don't know how to do this, Youtube is your friend.

For a short while, this seemed to do the trick.  Replacing both the battery and the power supply now keeps the PC running even after firing-up the laser printer.  Later, after adding a new 27" 4K monitor, the problem continued.  Disheartened, I came to the only remaining conclusion:  The old UPS, even with a new battery, was not doing the job. 

New UPS

As I was explaining this problem to my friends, they laughed at my UPS's age (19 years, 3 batteries).  It was time for a new one.  Today, it was replaced with a 600W 1100va UPS from APC.  The 600-watt rating is a coincidence and has nothing to do with the new power-supply.

Compliments to BestBuy for the price -- without prodding, they price-matched from $160 down to $130 with another online vendor.  Here it is, installed under the desk.

This time, I installed the USB monitoring cable and associated software.  During an extended power-event, the UPS shuts down the computer if I am not around.  And, it has a nifty adjustment to turn off the alarm if the PC is asleep between the hours of 10:00pm and 7:00am. 


Other Changes and a Wish:

Finally, I noted the laser-printer's power is plugged into a small, inexpensive outlet-extender, that also doubles as a cheap surge protector.

It has a green light, indicating all normal, but my green-light was red.  Although this was not the cause of my problem, it was also replaced.

Although the Laser printer and the PC/UPS are plugged into different outlets, they are on the same house-hold circuit (same circuit-breaker).  This is not enough to insulate the computer from the printer.

If I were building a new house, I would make two changes to the electrical.  First, I'd run 20-amp circuits, with 12-gauge wire to all rooms.  My house has 15-amps, 14-gauge, which is not enough to run two hair-dryers at the same time, let-alone a printer.   Secondly, I'd run a separate circuit for the printer.

Related articles:
UPS Batter Replacement APC CS-350
UPS Making clicking noise