computer chassis is energized if monitor cable is plugged in

[jsmith200]

I have a ViewSonic VA1938w-LED monitor. If I unplug the computer, plug in the monitor to an outlet, and connect the monitor cable to a desktop (no keyboard, no mouse), the desktop chassis is energized, as indicated by a lighted neon light tester, even if the monitor is not turned on.

If I take another monitor of the same model, plug in to another computer (different monitor, though same brand and model, different cable, different computer), again, the chassis is energized.

I wonder if this behavior is by design.

 

[gasaraki]

No. Also I don't really understand you. If you "unplug" the power from the computer, how is the computer "energized"?

 

[jsmith200]

No. Also I don't really understand you. If you "unplug" the power from the computer, how is the computer "energized"?

The only thing that was plugged in was the monitor. So, power must have gone from the monitor through the monitor cable to the desktop. Was there another way the computer could have gotten power? I can't see any other way.

 

[jay32267]

The chassis of anything should never be energized ever.

Check your outlet that you have the monitor plugged into.

 

[gdmaclew]

I agree with Jay.
Get an outlet tester like this one and tes the outlet.

https://www.blackrocktools.com/klein-receptacle-tester-rt100.html?gclid=EAIaIQobChMIxbvZyvP92QIVQmSGCh1d4gwhEAQYAiABEgKLdfD_BwE&s_kwcid=AL!3645!3!170114665336!!!g!!&ef_id=WrKQ5AAAAGBoon4Z:20180321170725:s

You may have an intermittent short to ground. (assuming that your outlet has a ground plug).
Very important!

 

[jsmith200]

I agree with Jay.
Get an outlet tester like this one and tes the outlet.

https://www.blackrocktools.com/klein-receptacle-tester-rt100.html?gclid=EAIaIQobChMIxbvZyvP92QIVQmSGCh1d4gwhEAQYAiABEgKLdfD_BwE&s_kwcid=AL!3645!3!170114665336!!!g!!&ef_id=WrKQ5AAAAGBoon4Z:20180321170725:s

You may have an intermittent short to ground. (assuming that your outlet has a ground plug).
Very important!

I checked the power cable. It has a two-prone plug. Obviously, the computer cannot be grounded. Even so, I wonder if the computer is designed in such a way that a low voltage is fed to the chassis.

 

[jsmith200]

I changed the power cord to one with a 3-prone plug. Now, the chassis is no longer energized.

Still, should the chassis be energized if the computer is not grounded? I don't know but I doubt it.What about all the energy that goes to the ground? That's a pure waste, isn't it?

 

[jay32267]

Here's what's going on. With the two prong plug, the chassis wasn't grounded. There is current leaking to the chassis somewhere. This causes the voltage on the chassis to depart from ground and the chassis becomes energized.

When you used the 3 prong plug...you grounded the chassis so it can't become energized.

...and you are right about the leakage current is now flowing to ground....but it is most likely VERY small. I wouldn't be concerned. This could almost be called "normal".....which is one of the reasons the chassis is grounded to begin with.