90 Watt power adapter issues, hum, crackle, tingle

This question is regarding the 90 watt AC-only power adapter supplied with the E6520 Lattitude series Dell laptops.

I see there have been a few posts about the tingling sensation that one gets when touching the top case rear metal cover (this is present on any metal part ground surface on the machine), and also the noises and crackling and hum that is heard when using audio devices like headphones, USB audio, etc.

First off, as an engineer and one who has access to the required test equipment to troubleshoot this, I can state that in the various locations I have tested this, i.e. the computer room at work where we have a million-dollar ground system and isolation, at home, in the shop at work, all which are properly wired and to code, I get these effects. I have tested this on 4 samples of the laptops and 4 samples of the power adapters. A cursory run around the IT area has me seeing the give-away tingle on any hardware matching this if I can get any contact with a real ground. I am measuring anywhere between 25 and 50 microamperes of AC leakage on the samples I tested and an AC voltage in the 25 plus range at the high-impedance non-grounded case of the laptop when using the 90 watt power adapter.

A few facts...

The 90 watt adaptor is a 3-wire unit. It is plugged into a properly grounded outlet. I tested 4 systems, and more were sampled, that exhibit this behavior with the 90 watt power adaptor. All exhibit the tingling and audio issues. *None* exhibit any of these issues when using the older 65 watt power adaptor (however that adapter runs hot.) None exhibit the issues when plugged into a lab-grade AC  isolation transformer. None exhibit these issues on battery power. If you unplug the power cord the issues immediately disappear.

Now for some conclusions...

No one seeing this is likely using a poorly grounded outlet nor is this behavior normal at all. The issue follows the 90 watt power adapter. A key difference between the 65 watt and the 90 watt power adapters is that when you measure from the third-wire of the AC power plug (the ground pin) on the 65 watt power adapter you see a true ground between there and the laptop power plug's outer shell. This grounds the laptop's metal parts. This is clearly connected and very low resistance. When you make that same reading on a 90 watt power adaptor you see an approximately 1 megohm resistance between the power plug ground pin and the laptop power plug's outer shell. This is clearly *not* grounding the metal parts of the laptop as the 65 watt adapter does. The 90 watt unit is very light, the 65 watt much heavier. I can't see inside these units, but it's obvious that there is a transformer in the 65 watt AC/DC unit because of the weight, and I'm not sure what the design of the 90 watt is. One thing is for sure, the 90 watt unit is not grounding the laptop metal parts as it should be, and the design of this 90 watt adapter is certainly in question for me. Especially based on my and other's symptoms. I can't even see this as safe for anyone wearing a pacemaker, etc.

Because I sampled a few units and laptops I do not believe this is simply a defective parts problem that can be swapped to fix the issue, unless the swap is to another part/design entirely. And, the current adapter is useless for any interfacing or audio uses, external serial ports via the ExpressCard slots, etc., because of this.

Now a request...

Is there anyone else that can verify this on your own hardware. I tested the grounding of the 65 watt adapter on a fairly big sample and all are grounded and none exhibit the 90 watt adapter's issues.

Does anyone have access to a multimeter and a 130 watt adapter to test this model for ground connections and to see if it cures the issues of the 90 watt adapter? Is the 130 watt adapter even compatible with the E6520?

I'm not sure where at Dell to go with this or what their stance will be, but these 90 watt power adapters are definitely a problem. I'm disappointed that unlike the older adapter they do not offer a combined AC/DC capaility at the 90 watt power level. But, I can live with a separate DC adapter as long as the AC adapter is a proper design and does not cause these issues.

I'm looking for answers and a solution to these issues. And any ideas or comments are greatly appreciated.