[RFI] Whirlpool Duet Washing Machine RFI update

[Pete Smith]

Leigh, do I understand correctly that these parts haven't yet been 
installed?  If so, my suggestion would be to let them install them in the 
stock fashion and see what happens to your noise problem.  If they went to 
this much trouble to fix it, the new control system may be clean.  By all 
means DON'T mess around with shielding or beads until you know -- I suspect 
doing anything like that could void your warranty.

73, Pete N4ZR

At 08:40 PM 2/10/2005, Leigh L. Klotz, Jr. wrote:

>Here is an update on my Whirlpool Duet problem.
>
>I have a Whirlpool Duet front-loading washer, which I think uses a 
>variable-frequency AC motor and a fairly complicated mpu control system.
>I've reported this here before, and also have talked to the Whirlpool 
>people.  I now have a new set of innards, and the new news here is 
>pictures of them at http://wa5znu.org/2005/01/duet/parts/
>
>I am seeking advice as to whether I should try shielding them with copper 
>tape or foil, or at the very least putting some ferrite beads on the 
>control cables, or if I should just let nature take its course and let the 
>service people put in the new parts as is.
>
>Also, if anybody has recommendations for RF-quiet front-loading washers, 
>my wife has fortunately agreed that if the problem can be solved by 
>selling this unit and buying a new one, we can do that.  (If you would 
>like to buy a slightly used Whirlpool Duet spark gap transmitter, works on 
>all bands, please contact me offlist, hi hi.)
>
>Details below.
>
>73,
>Leigh WA5ZNU
>
>*Kinds of Noise*
>
>The washer makes at least 3 kinds of noise.
>1. When it's off or on, there's some hash.
>I assume this is from a switching power supply, or possibly the MPU.
>I don't have images of this noise off and on.
>
>2. When the drum is spinning, it makes both broad noise and discrete noise 
>about every 17KHz
>The noise extends up well past 20M.  I have audio spectrum images at
>http://wa5znu.org/2005/01/duet/noise/
>
>You can see the discrete noise clearly in the 4th and 7th images.  To the 
>left of the blue line is foreign BCB.  To the right is the discrete noise 
>starting.
>
>
>The broad noise "washes out" everything for me, and the discrete noise is 
>maybe 10dB above that.
>You can see the effect of the broad noise effect in the 3rd and 5th images 
>on the web page.  The weak PSK signal disappears when the noise 
>starts.  The rolloff below 500 and above 2500Hz is system audio response.
>
>3. It makes other discrete noise when the water pump is running.
>
>*Sources of noise*
>I took my Elecraft KX1 with a short piece of wire as an antenna and found 
>that little noise came from the power cable.
>However, tremendous noise came from the front panel.  In fact, I can pick 
>it up there on a cheap FM broadcast radio with no antenna.
>There is much less noise to the sides of the washer, where metal is 
>between it and the front panel.
>
>*What I've done so far
>*A Radio Shack AC line filter did nothing but it did show me that the 3rd 
>prong is grounded.
>An ohmeter shows <1 Ohm between the 3rd prong and the water pipes.
>Bonding the washer 3rd prong to the water pipe did nothing.
>
>*What Whirlpool did
>*Whirlpool said that their Part 15 data was proprietary.
>I checked and appliances (except microwaves) are not required to be 
>submitted for certification.
>Sure enough, Whirlpool has FCC Part 15 data filed with the FCC only for 
>microwaves.
>
>Whirlpool said that the control board and front panel are unshielded.
>They spent a bit of time talking to me on the phone, and their engineers 
>looked at my audio spectra.  They sent me a new set of innards -- motor, 
>control board, AC line filter, and front panel, for free (out of warranty) 
>and said that if that didn't fix it they didn't know what to do.  They 
>said the controller is made in Germany, but that it is not sold in the EU 
>(I thought maybe they'd designed it for CE but removed parts not 
>required.)  They said this is their 3rd product with an MPU instead of a 
>mechanical controller.  They also said they have no other RFI reports so far.
>
>I have pictures of the parts at http://wa5znu.org/2005/01/duet/parts/
>
>*What do I do now?*
>So I think the service call is going to be on my dime, and I don't know 
>what to do next.
>
>1. Call and have the new parts installed and probably get no result.
>2. Try to retrofit copper shielding into the control board box and front 
>panel and hope the service installer doesn't notice.
>3. Clamp a few ferrites on the wires in the front panel and hope for the best.
>4. Do #1, but if there is no result, try to get the ARRL or the FCC involved.
>5. Sell the washer and buy a different brand that might or might not 
>generate RFI.
>
>
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