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Author Topic: *%&$^& Dell Laptop Power Supply!  (Read 11405 times)
W1ES
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Posts: 18




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« on: June 20, 2010, 06:34:33 PM »

Figured I'd improve my computer situation bu getting a laptop and a docking station for the shack.  A great concept: I can use the computer for other things besides my radio.  Thought I had a win-win.
My Yaesu FT-680 is completely trashed on 6m by the switching power supply that this computer uses!  40 over S9.  Tried enclosing everything in tinfoil and braid and that knocked it down to 20 over.  Curiously enough, the FT-1000D right next to it isn't affected nearly as much (though it is detectable).

OK, I thought, I'll get a 20V linear power supply and solve my problem.  Uh-uh.  The docking station will NOT work without that third wire signal in the Dell power supply.  I'd like to take the person at Dell who came up with this idea and have a few minutes alone with him  Angry

Do any of you have a circuit that can fool the D610 into thinking it's seeing a "legit" supply?  I really don't want to have to find another computer.  There has to be a cheap way of doing this.

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WX7G
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« Reply #1 on: June 21, 2010, 08:12:22 AM »

Is it the PC power supply or the docking station power supply that is causing the RFI?
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W1ES
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Posts: 18




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« Reply #2 on: June 21, 2010, 09:05:56 AM »

Both; they're identical.

I've also heard a rumor that there's a way of defeating this from setup or in the firmware.  Ever hear of it?

Again, the supply is a round connector, V- (GND) on the outside, +19V inside the barrel and a "special" signal on the tiny pin in the centre.

I'd like to know if there's an easy way to either replicate the signal or voltage on the centre pin, of make the computer ignore it.

TNX

Steve, W1ES/4
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WX7G
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« Reply #3 on: June 21, 2010, 10:27:37 AM »

Without the docking station - with the PC and one power supply - is there still RFI?
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KF7CG
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Posts: 836




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« Reply #4 on: June 21, 2010, 10:50:31 AM »

It ain't just Dell! I my house we have both A Dell laptop and a couple of HP laptops. All 17" and all use the same power supply type hookup. No discernable RFI from any of them, but they are 20' feet from my analog supply power FT-950.

No docking stations for any. My "radio" computer is an old Gateway with a totally screw together case and it is quite noise free too. Probably due to the way the case is constructed and the older model power supply with good EMI filtering.

That third wire is the battery condition/ac power condition sense line.

KF7CG
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W1ES
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Posts: 18




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« Reply #5 on: June 21, 2010, 12:02:56 PM »

What do I need to provide for the "sense line"?

Yeah, I know I can have a quieter setup with a different computer - but I have my money sunk in THIS computer.

The racket is there whether or not the computer is plugged in, whether or not the docking station is plugged in.  Running shield over the power out line and tinfoil around the "box" cut the noise some, but not nearly enough (Think decrease in level from a top fuel dragster at full throttle to a Harley and you're there ;-)  )

The noise remains after I unplug until the supply bleeds down to zero.

What now?  Faraday cage for the power supply with feedthrough caps?  Arrrgggggggghhhhhhhhh!
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AA4HA
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« Reply #6 on: June 21, 2010, 03:34:03 PM »

That extra line communicates using the I2C protocol ( http://www.i2c-bus.org/ ) to a chip in the supply that provides an "identity" of the power supply back to the BIOS on the motherboard. It is how the laptop knows that the supply is of sufficient capacity to run the laptop at full speed and to charge the battery.

As you found, if you do not provide that bus connection the laptop will throw up a message like "Unable to detect the power supply, the laptop will run at reduced speed or may not charge".

Dull Laptops are stinkers for wanting a supply at least large enough to run at full speed. You get into the same problem if you use an undersize supply to run a laptop or if you have damaged the connection on the back of the laptop (broken a solder connection at the PCB for the plug).

The laptop will probably run but it will not charge the battery.

Tisha Hayes
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
W1ES
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Posts: 18




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« Reply #7 on: June 21, 2010, 05:31:57 PM »

In my case, I'm perfectly willing to run a supply with plenty of capacity.  I'm not looking for this to be cheap, I'm looking for this way out so I can use my laptop with my station without it trashing my reception.

I've heard that there may be a way of disabling this in BIOS or setup.  Any ideas in that direction?  I'm a big boy and can determine my own power requirements.

This will be the last Dell I purchase, ga-rawn-teed!

73,

Steve, W1ES/4
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KF7CG
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Posts: 836




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« Reply #8 on: June 22, 2010, 04:55:21 AM »

HPs are no solution, they use the same p0wer supply configuration also made in China! These supplies depend on signals back from the computer as they have to adapt to the battery in the computer at the time. 6 cell batteries are about 18 to 20 volts, 9 cell batteries higher, and 12 cell batteries like 6 cell units but at twice the current.

These are not dumb supplies, they are more like smart charger.

I have both HP and Dell laptops in myhouse, not recommended but they can swap supplies if really necessary.

KF7CG
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W1ES
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Posts: 18




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« Reply #9 on: June 22, 2010, 05:54:25 AM »

Alright, so has ANYONE succeeded in quieting these damn things down?  Am I forever stuck with either putting up with the racket, using the computer only 2 hours at a time or giving up and going back to a desktop?

One way I could try would be to sell the dock and get one for the Toshiba, but I really don't want to have to deal with dongles for the keying and comms to the rig!  I specifically bought this Dell because it was one of the last of the laptops with legacy ports.
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WX7G
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« Reply #10 on: June 22, 2010, 06:25:14 AM »

Have you considered opening up the lap top power supply, disconnecting the DC output of the switching power supply, and applying your 20 VDC at that point? The third wire is then still connected to the power supply circuitry.
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W1ES
Member

Posts: 18




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« Reply #11 on: June 22, 2010, 06:32:50 AM »

That wouldn't do anything to stop the RFI.

Some more observations about this incredibly RF-dirty supply:

S9 +40 db on entire 6m band - white noise (not pulsing, not buzzing, just broadband white noise)
S5 or so on HF bands on my 1000D.

I wonder if this is getting into an IF, as it makes no sense that the lower bands are better - unless this really is 50 MHz trash.

Shielded body and ran power output cord through braid - noise went to S9 +10 or so on 6.

Unplug open supply, noise stays until caps inside supply discharge.  Remove power cord at supply, same amount of noise until caps discharge.

I'm about ready to bust this thing open and have a look tonight.

Dell is still on my "Duty-list" for this!

73,

Steve, W1ES/4
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WX7G
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« Reply #12 on: June 22, 2010, 08:42:16 AM »

It wouldn't do anything to stop the RFI? It shuts the power supply OFF. You unplug the Dell power supply. That means no RFI.

You substitute your quiet linear power supply for the noisy Dell switching power supply.
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W1ES
Member

Posts: 18




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« Reply #13 on: June 22, 2010, 08:52:48 AM »

I guess I'm not understanding the concept here.  Does the "proprietary device" operate with no power supplied to it? That and the fact that you'd be connected to only one wire don't make any sense to me.

W1ES
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KF7CG
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Posts: 836




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« Reply #14 on: June 22, 2010, 11:05:57 AM »

Get with Dell Customer Service and ask them for help. If the computer is still in warranty, you may be shipped another power supply immediately and then have to return the old one at Dell's expense.

That is how I have had to handle some of the repairs on my HPs; no need for work on the Dell. We have a couple of HP Laptops at my house along with a Dell laptop none of these cause any radio noise that I can find. The Dell is about 1 month old the HPs are a little over a year. One laptop per person.

Since my Dell laptop doesn't cause any trouble, I would guess that at least one Dell supply is noise free. The HPs use the same type power hookup and they are noise free so it may be the one instance of a power supply that you have.

KF7CG
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