Having a really weird LCD issue.

[Dputiger]

Ok, I'm going to lay this out as thoroughly as possible. I have a Pioneer SX-3600 receiver hooked to two Advent Loudspeakers. This system operates perfectly and has for some years.

Recently I began hearing a high-pitched whining from the speakers that persisted no matter what input channel (Tape 1 or Tape 2) they were hooked to. The sound is markedly different from the deep "BZZZ" that sounds when you accidentally touch metal with an active speaker line.

Here is what I have discovered:

If my LCD is plugged into the video card (which is DVI only--and I use a DVI LCD) the high-pitched whining occurs. If I unplug the LCD, the whining IMMEDIATELY stops.

Other notable events:

Touching the DVI panel anywhere to the back case panel immediately recreates the sound. Touching the 1/8 speaker cable end directly to the DVI metal also creates the sound at a much louder volume (but identical pitch).

Switching the 1/8 speaker wire does not have any effect.

Changing the DVI cable does not matter. Nor does using the LCD's optional RGB output and fitting a converter on to my video card.

Using a different power cable (into the LCD power pack) does not matter.

For a brief period of time the sound seemed less if I move the LCD power pack away from the other cabling. This no longer appears to be the case.

The problem persists even when a different video card is used or when my sound card is REMOVED from the system. I can plug my speakers into the NON-ACTIVE audio ports on the motherboard (which don't even have drivers installed) and I will still hear the sound.

The sound does NOT occur when the LCD is in stand-by mode. Only when awake.

Finally--

Switching to my backup 19" monitor solved the problem.

Now, I have NO idea what is wrong. It seems as though there is a short in the system at some point but the only thing I know of to do is take the whole system apart at this point and I'm REALLY trying to avoid that. Does ANYONE have ANY suggestions? Please read through this carefully so you don't end up repeating steps I've taken--I've done a thorough job of testing what cables I could before posting.

All help appreciated.

[cadetstimp]

Sounds like a grounding issue and that your LCD is collecting/producing excess static which is being transmitted through the video card.

Because your monitor (LCD or CRT) usually has its own power supply - it's important that is grounded and sheilded properly to prevent it from affecting your system through the video card.

Does your LCD use a 3 prong grounded power cable?

If the CRT is better sheilded and makes better use of a grounded plug ... then it wouldn't create the same problem. The problem could be the LCD itself if it is not properly grounded/sheilded due to design, assembly, damage, defect, etc.

It looks like you've done a good job troubleshooting. Since the CRT doesn't cause the same problem, I would lean towards the problem NOT being your system, but the LCD itself.

[Dputiger]

Both monitors use a grounded cable and I have tried replacing the second half of the LCD power cable.

(the LCD power is in two parts. First part is a plug from the monitor to an external transformer. Second part is a standard computer power plug to the wall. I have replaced the second part with no effect).