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Washing Machine RFI Cured

(K2UP) on October 20, 2005
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Washing Machine RFI - Cured

Last month, Leigh Klotz, Jr. (WA5ZNU) posted an article about the RFI generated by his Whirlpool Duet washer and dryer. I read with interest as my Sears Kenmore HE3 was also producing severe RFI on all the HF bands. Among the various helpful, humorous and sick-troll responses, N4EKV suggested an A/C line filter from Filter Concepts. I decided to try ferrite beads and the A/C filter approach. (http://www.filterconcepts.com).

When I opened my machine - SURPRISE ! There was an A/C line filter already installed. A small, black one, pictured above. So, I started with the ferrite beads. I put them on the wires leading to the control panel and to the main motor assembly. The beads are not the newest type. They knocked the RFI down a few db but did not stop the problem.

To avoid invalidating any warranty, I chose to use the A/C filter externally. I put the SF20 in a box and attached the ends of a spliced extension cord to it, so that the filter could be used at the point where the washing machine plugs into the wall outlet. A 15 amp capacity filter would probably be fine, but I wanted the option of using the filter for other applications in the future and opted for the 20 amp capacity.

As many had speculated, the A/C wiring in my house was acting as an RFI conduit. The line filter cured the problem for me. I am not sure whether it's worth it to keep the ferrite beads in place. But there is no harm there. The machine works fine with them in place.

Thanks again, Adam (N4EKV) and all the others who poster helpful comments.

Member Comments:
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Washing Machine RFI Cured  
by N0IU on October 20, 2005 Mail this to a friend!
I have been to a few hamfests where some of the attendees could benefit from this article. Not that they have a problem with RFI, but there are such devices out there known as washing machines! HIHI
 
RE: Washing Machine RFI Cured  
by K3AN on October 20, 2005 Mail this to a friend!
Since a washing machine enclosure is (for now) made of metal, it's probably a pretty good shield, meaning the RFI gets out mainly via the power cord. It's great news that the AC line filter worked. It will become my first choice remedy when (not if) such a "bad actor" ends up in my house.
 
RE: Washing Machine RFI Cured  
by K0BG on October 20, 2005 Mail this to a friend!
Interesting. Even without knowing what values of components were inside the black device, I'm surprised the new additional filter it fixed the problem. The Sears model we have is identical except for some minor marketing differences. I tried to use a brute force filter, and it had no effect whatsoever.

The CPU in these things are not well shielded, and apparently Sears is aware of it. One of the local repair guys told me it is a common complaint. He said he recently replaced one of their units free of charge even though it was out of warranty for an RFI problem with an off-air TV.

As I stated in my post to the original article, a few well placed Mix 31 beads fixed the problem. A cap and a varistor fixed the noise generated by the clutch relay.

It is my opinion that there are several different models with basically the same electronics. I further suspect the placement of the CPU module inside the units effect how much RFI they generate.

It's nice to know you cured your problem, however, it may or may not be applicable to other similar models.

Alan, KBG
www.k0bg.com
 
Washing Machine RFI Cured  
by KB7LYM on October 20, 2005 Mail this to a friend!
I have complety solved the problem of RFI on my aging Sears washing machine. HF now clear as a bell. No disturbance at all. After loading my double barrel Shotgun and after 4 shots of close range.. the problem was over. No need for filter and out of pocket $$$

You all have a good day and i will wash my socks by hand.

KB7LYM
 
RE: Washing Machine RFI Cured  
by WB4M on October 20, 2005 Mail this to a friend!
N0IU: Hahaha.. why put clean clothes on if you don't bathe? :)
 
RE: Washing Machine RFI Cured  
by WA6BFH on October 20, 2005 Mail this to a friend!

Of course having the filter external, is not as effective as having it more closely associated with the noise generating electronics.

It just goes to show you though. So, why do you suppose that manufacturers use cheap ineffective filters in their products?

Who made this washing machine?
 
Washing Machine RFI Cured  
by WA1RNE on October 20, 2005 Mail this to a friend!
K2UP;


Great to see you found a good solution.

However, you may want to try something that may be simpler.

Looking at the case of the original OEM filter, you will notice a schematic of the internal filter.

On the load side, there is only a single capacitor connected line to line which is used for differential mode filtering.

There are no *line to ground* or "common mode" connected capacitors which may be all this filter needs to attenuate the noise you are experiencing.

Allthough the Filter Concepts unit does include additional differential mode inductors on the load side, the 2 common mode capacitors connected line to ground may be all that's required - as opposed to a second externally connected filter.


73, Chris
 
RE: Washing Machine RFI Cured  
by WA5ZNU on October 20, 2005 Mail this to a friend!
FB on the RFI fix OM! I think this will work some brands. I am interested to know: Is the front panel on yours metal or plastic? The electronics and motor control on mine is totally unshielded...

I have heard from a number of OMs who fixed their problems with an AC line filter, but one reason I didn't think an AC line filter would be effective in my case was tests I did using an AM radio, an HT, and a KX1 HF receiver.

Here is the test I did: I put the receiver next to the power plug and found almost no noise, but there was plenty coming from the plastic front (not the sides) of the Whirlpool Duet. (A few people did suggest that I could eliminate the radiated inteference by moving my antenna to a tower located 150ft from the house and make sure my feed line was properly balanced. Unfortunately that would be about 3 houses away, hi hi.)
 
Washing Machine RFI Cured  
by K2UP on October 20, 2005 Mail this to a friend!
I think that Chris (WA1RNE) has a point when he wrote:

"There are no *line to ground* or "common mode" connected capacitors which may be all this filter needs to attenuate the noise you are experiencing."

I may try that next. Also, I read recently that the plastic covers on many snap-on ferrite beads don't hold the ferrite halves together so they make contact. This produces inferior results. For these snap-ons, it is recommended that they be removed from the plastic, placed around the target cable, then held tightly together with plastic friction cable ties. Just something to think about.

Since the beads are not the famous Mix-31, that is another thing to try. Mix-31 is supposed to be more effective for the HF bands.

My Washer has plastic face plate parts. I wouldn't be surprised if I was experiencing RFI radiated from the control panel as well as RFI carried on the AC lines. The beads may have lessened the control panel contribution.

You can actually see the values on the machine's line filter. It looks like it ought to work. But it doesn't work well enough. Maybe those line-to-ground capacitors explain it. If my experiment works, I'll let Sears know. A different filter may cost relatively little more and solve the problem for some machines.

Rob K2UP
 
RE: Washing Machine RFI Cured  
by W6TH on October 20, 2005 Mail this to a friend!
.
Reminds me of the days when the "IF's" were 21 Mhz on the television sets and the 3rd harmonic of 7Mhz fell into the "IF's" as well as the 15 meter band (21 Mhz).

Need you hams to be working for the FCC and also with these washing machine companies. To show them that ham radio is a service.

.:
 
RE: Washing Machine RFI Cured  
by WA1RNE on October 20, 2005 Mail this to a friend!

Rob;


In this application, installing a ferrite "bead" around a single line or load wire creates a differential mode choke.


The problem is, it's not going to be very effective differential mode choke if:

a) the noise is being created by a 20-250 kilohertz frequency range switching converter, and ..

b) its permeability is high at HF.


The small snap-on beads will work for choking off *HF* noise getting into an audio amplifier or as a common-mode choke on a CATV line for RFI problems, etc., but not much at switching converter frequencies. Assuming the cause is switching converter noise, the choke will need to have much more inductance - and impedance near the switching frequency, requiring a larger core and of different material.


Bottom line, you should get more bang for the buck with a 0.047uF to 0.2uF capacitor from each line to ground - on the load side of the filter.

Be sure to stay conservative on the voltage rating - like 2x the peak AC input voltage, or 400 vdc rated or better.


Otherwise, the commercially designed EMI filter is the way to go - save additional time probing around with a scope to find the noise then suppress it at the source which can be much more difficult.


73, Chris
 
RE: Washing Machine RFI Cured  
by W0NFU on October 21, 2005 Mail this to a friend!
Seems to me that an important issue has not been addressed.

These incidents should be reported to the FCC. Part 15, if I remember the section correctly, requires manufacturers to clean up their equipment. Of course, I'd hate to have to wait for action but still the FCC should be made aware of the problem.

Larry WNFU
 
RE: Washing Machine RFI Cured  
by KE3HO on October 21, 2005 Mail this to a friend!
>>The small snap-on beads will work for choking off *HF* noise getting into an audio amplifier or as a common-mode choke on a CATV line for RFI problems, etc., but not much at switching converter frequencies. Assuming the cause is switching converter noise, the choke will need to have much more inductance - and impedance near the switching frequency, requiring a larger core and of different material. <<

You don't have to choke off the fundamental frequency to eliminate the HF noise. The problem with switching power supplies is that they use square/rectangular waveforms in the converters. These waveforms have very fast rise/fall times - this is fundamentally necessary for high efficiency (low switching losses in the mosfets). If you recall Fourier theory, a square or rectangular waveform requires many many harmonics to get that sharp waveform. These harmonics radiate form the system, and often the worst places for radiation are the wires attached to the system. You can attenuate the HF on these wires with ferrite beads without having to filter out the fundamental switching frequency of the converter, or the fundamental clock frequency of the CPU, or whatever the source of the signal is. Switching power supplies are a bigger problem than CPU's for example, because these square/rectangular waveforms often are at significant current levels (amps rather than the microamps or milliamps associated with CPU/digital circuits), so the power in the harmonics is higher as well.

73 - Jim
 
RE: Washing Machine RFI Cured  
by WA6BFH on October 21, 2005 Mail this to a friend!

Joining nudist colony, will sell washing machine cheap!
 
RE: Washing Machine RFI Cured  
by WA1RNE on October 24, 2005 Mail this to a friend!
Jim;


My intent was to offer some simple practical advice without writing a complicated dissertation on EMI filter design. (BTW, I am quite familiar with the waveforms used in switchers and Fourier Series. I ran my first one with an HP-85 computer back in 1981. Remember tape drives?)

I didn't say a differential mode choke should be designed at the switching frequency, but admit that it came off sounding like that. What I was trying to point out was, that for this application, placing a ferrite between this particular OEM line filter and the switcher (and any other devices down stream) is not a very good choice for a differential mode choke.

With the type of EMI filter design used by the OEM, the common-mode choke is likely designed with a powdered iron toroid and has a wide band response through 30 Mhz or more. Adding differential mode chokes would then aid in suppressing signals < 2 Mhz, but it varies depending on the filter and choke design. In this case, that's unknown.

Going by the diagram in the photo, this particular OEM filter consists of a common mode choke and a line to line connected capacitor for differential mode decoupling.

The real problem is, the filter doesn't contain any common-mode decoupling capacitors. If in fact we are dealing with switcher noise, these capacitors are vital for decoupling leakage currents away from the power line. The leakage currents emanate from the primary switch, transformer, etc. and are mostly capacitively coupled to earth ground. As you stated, the harmonic currents are higher in a switcher compared to a CPU running at say 5 vdc. Given the high voltages generated in the primary circuit of the supply, this creates signicant leakage currents through just picofarads of capacitance. These currents must be blocked and re-directed away from the power line or they will radiate from the line and/or the connected appliance wiring.

The common-mode choke and the common-mode connected capacitors work together to decouple harmonic currents from the line (hot and neutral) and earth ground.

So adding a couple of ferrites to the hot and neutral sides of the line might help but not nearly enough to make this "tub" really quiet across the broadcast band through 30 Mhz.


73, Chris
 
Washing Machine RFI Cured  
by KJ7WT on November 4, 2005 Mail this to a friend!
I'd like to add another note to this whole thread - I was about ready to hit something after I got my new IC-718. I have been inactive for many years & decided to get back on the air. I built an off-center fed dipole & got the rig going & what I found was an enormous amount of RFI. I started switching off/unplugging pretty much everything I could think of, with no effect. Finally, I thought of my daughter's room, which had a TV & DVD player. I unplugged both of those, but no relief. Then, I noticed her cell 'phone charger. Unplugging THAT brought the noise to a halt! I plugged it back in to do an A/B/A check, and sure enough, the loud, raspy noise on everything up through 15 meters followed the charger. Since then, I've had the pleasure of relatively quiet QSO's.
 
Washing Machine RFI Cured  
by K9GLN on November 6, 2005 Mail this to a friend!
I greatly enjoyed this thread and hope some of the remedies will work for me.

I have had relatively few RFI problems but the washing machine has been a RFI problem with me as long as I have been a ham. Quite honestly I was afraid there was a grounding issue bewteen my main house electrical panel and the service in the utility room. I have checked several times for loose wires and or other problems. Everytime the washer spins out, I get RFI, even in my bedroom alarm/AM radio. I can even tell if the washer is spinning when I pull the car into theb garage just from the noise on the radio.

Thanks for the ideas!

Glenn
 
RE: Washing Machine RFI Cured  
by N1PTB on December 3, 2005 Mail this to a friend!
I am an All Products Tech at Sears in Waterford,CT for the past 17 years. I had a customer with a Kenmore front load washing machine that was made by Frigidaire and was having horrible RFI. This customer is an avid SWL. I went to his home and tried supression beads with little effect. Next day, I called my contact at Frigidaire who connected me to engineering who said we have an RFI kit for these situations. I installed the kit(a huge cap) inline with the ac cord inside the cabinet. All RFI was gone every bit of it. I will use my contacts at Whirlpool to see if there is a kit for the WHirlpool Duet,Kenmore HE2,HE3,and HE4 series washers. I will also test out a Maytag Neptune in the store to see how that washer fairs as to RFI problems. I post back ASAP with my findings.
73, Randy N1PTB
 
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