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Author Topic: BAD RFI from My Toshiba Laptop power supply  (Read 6662 times)
VK2LEE
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« on: August 31, 2014, 08:37:36 AM »


Well I've noticed that I have between S7 to S9 of noise level most of the time on HF on My Yaesu FT920.  I have gone around the house at times switching 12v DC LED down lights off and the many 240vAC sensor lamps I have outside that all have 85-240V LED bulbs in them. I couldn't find anything that would lower the Noise in My 920. I have horizontal dipoles for 20 and 40m and Inverted Vee's for 80 and 40m. I also have 4 element Yagis for 10 & 15M on top of a tower but I haven't used them for a while.
Today, I thought I have to find what is causing all this noise which is always there.. I pulled an old portable shortwave receiver out and pulled the whip antenna up and went all over the house trying to find the source of the noise.. I did find one outside 240v LED lamp was noisy and 2 x 12v DC warm white LED down lamps noisy, the rest were cool white 12v LEDs and were no problem. I did find that Our Dyson cordless vacuum cleaner which is always plugged into its charger, was VERY noisy..  Only two of the many 240v AC - 9-12v DC plug packs [switch mode] I have thru the house was noisy. I then returned to My Ham Radio Room with the portable radio after switching everything I had found noisy, Off. As soon as I went near My Radio equipment with My Toshiba laptop on the shelf below them, the noise from the portable radio was very Loud. The Power supply for My laptop was the major cause of RFI in My 920.. When I disconnected the power supply, I lost S7-S9 of Noise level instantly...  Then I remembered that I had to replace My battery charger/power supply for My Toshiba Laptop [a few months ago]. My laptop is usually always connected to the 240vAC - 19v DC battery charger.  The charger is usually about 3-4 feet from the 920. But it was sitting next to the laptop today and at first I thought the laptop was the problem.. YIKES..   and the power supply isn't a genuine Toshiba.... so.. I'll have to try a genuine charger and I hope it will be RFI noise free...

Lee  VK2LEE

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28 years as VK2LEE - The 1st 3 letter L call ever issued - in 1986 -
WX7G
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Posts: 6334




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« Reply #1 on: August 31, 2014, 03:21:36 PM »

Ferrite cores placed on the wall wart DC or AC cable might help and the only way to find out is to try them. You can expect an improvement of a few S-units. Or as you say try a Toshiba wall wart. Note that an EMC compliant device (legal) can cause noise at the levels you report.

That's a lot of work to find a noisy device. The usual method is to run the transceiver on a battery and shut off all the power to the house. If the noise goes away the power is switched on one room at a time. Once the room with the noisy device is found devices in the room are unplugged one at a time. No need for a portable receiver.

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ZENKI
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Posts: 997




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« Reply #2 on: September 01, 2014, 03:59:52 AM »

No surprises there  just about ALL aftermarket lap top power supplies are CRAP.  Get a genuine one or try and find a compatible one from Lenovo or some other reputable company. The genuine toshiba power supplies are very good generally.

In my experience its very hard to silence these after market power supplies even using a ton of toroid cores on both input and output.
Any EMC compliant power supply should not be so horrendously noisy. They all emit birdies which  generally dont extend much above 80 meters with 160 meters being the most affected.

I have done a lot of work with cheap power supplies and  toroids are not a fix for power supply that has EMC parts removed internally. This is the case with most aftermarket power supplies. The same goes for after market cell phone chargers they horrendous   and even multiple #31 cores wont kill the interference.

I like buying after market power supplies from big name companies and then if they are bad I can at least get my money back or threaten them with consumer law  complaints if they dont refund. I know I can win my case everytime if they do resist.

You wont succeed fixing  a dog of a power supply with ferrites, been there done that a million times and failed! Destroy the dog!


"
DC warm white LED down lamps noisy, the rest were cool white 12v LEDs and were no problem. I did find that Our Dyson cordless vacuum cleaner which is always plugged into its charger, was VERY noisy..  Only two of the many 240v AC - 9-12v DC plug packs [switch mode] I have thru the house was noisy. I then returned to My Ham Radio Room with the portable radio after switching everything I had found noisy, Off. As soon as I went near My Radio equipment with My Toshiba laptop on the shelf below them, the noise from the portable radio was very Loud. The Power supply for My laptop was the major cause of RFI in My 920.. When I disconnected the power supply, I lost S7-S9 of Noise level instantly...  Then I remembered that I had to replace My battery charger/power supply for My Toshiba Laptop [a few months ago]. My laptop is usually always connected to the 240vAC - 19v DC battery charger.  The charger is usually about 3-4 feet from the 920. But it was sitting next to the laptop today and at first I thought the laptop was the problem.. YIKES..   and the power supply isn't a genuine Toshiba.... so.. I'll have to try a genuine charger and I hope it will be RFI noise free...

Lee  VK2LEE

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WA2ISE
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Posts: 183




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« Reply #3 on: September 04, 2014, 12:41:14 PM »

I had an RFI problem (trashing the AM broadcast band) with a Toshiba laptop ps, but I plugged it into a line EMI filter from Cornell Dubiler, nf-10869-389 and that quieted it down.  It's a 3 prong metal box with all the filter inside.
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NK7Z
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« Reply #4 on: September 04, 2014, 12:59:25 PM »


Well I've noticed that I have between S7 to S9 of noise level most of the time on HF on My Yaesu FT920.  I have gone around the house at times switching 12v DC LED down lights off and the many 240vAC sensor lamps I have outside that all have 85-240V LED bulbs in them. I couldn't find anything that would lower the Noise in My 920. I have horizontal dipoles for 20 and 40m and Inverted Vee's for 80 and 40m. I also have 4 element Yagis for 10 & 15M on top of a tower but I haven't used them for a while.
Today, I thought I have to find what is causing all this noise which is always there.. I pulled an old portable shortwave receiver out and pulled the whip antenna up and went all over the house trying to find the source of the noise.. I did find one outside 240v LED lamp was noisy and 2 x 12v DC warm white LED down lamps noisy, the rest were cool white 12v LEDs and were no problem. I did find that Our Dyson cordless vacuum cleaner which is always plugged into its charger, was VERY noisy..  Only two of the many 240v AC - 9-12v DC plug packs [switch mode] I have thru the house was noisy. I then returned to My Ham Radio Room with the portable radio after switching everything I had found noisy, Off. As soon as I went near My Radio equipment with My Toshiba laptop on the shelf below them, the noise from the portable radio was very Loud. The Power supply for My laptop was the major cause of RFI in My 920.. When I disconnected the power supply, I lost S7-S9 of Noise level instantly...  Then I remembered that I had to replace My battery charger/power supply for My Toshiba Laptop [a few months ago]. My laptop is usually always connected to the 240vAC - 19v DC battery charger.  The charger is usually about 3-4 feet from the 920. But it was sitting next to the laptop today and at first I thought the laptop was the problem.. YIKES..   and the power supply isn't a genuine Toshiba.... so.. I'll have to try a genuine charger and I hope it will be RFI noise free...

Lee  VK2LEE


I have a small article on quieting down the shack located at:

http://nk7z.net/rfi-now-house-cleaning/

It may help you in locating the various sources, and removing them...
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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
KL7CW
Member

Posts: 83




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« Reply #5 on: September 12, 2014, 08:34:03 PM »

Noise was getting into the audio system about 5 years at my church.  The noise source was a Dell power supply plugged into a Dell laptop computer which we use for both audio and video content.  I wound about 11 turns of the DC output cable of the power supply through a small do-nut size ferrite core and the noise was reduced below the detectable threshold at any reasonable audio gain setting.  There are many RF links, various audio and video sources, an overhead projector, various video monitors, etc. but since this simple solution "fixed" the problem I never investigated further.  Other Dell laptop power supplies also introduced audio noise into the system. I doubt that the choke had any significant chocking Z at audio frequencies, so presume it was RF getting into the equipment which produced the audio trouble.  Since the choke reduced the "RFI" by an estimated 10 to 20 dB, I assume it was probably RF somewhere in or near the HF spectrum, since (common mode) RFI reduction with a single choke is often in the 10 to 20 db range.  Normally I would investigate and track down the source, its frequency, etc. before trying a cure.  However I just happened to have a ferrite core in my tool box and my spectrum analyzer and scope were at home...so I just tried the core.....I got lucky....fixed and all is still quiet and the whole thing only took 5 minutes....still quiet 5 years later.  Not all fixes are this easy and usually measurements and a thought out plan work better than simply trying things !!
   Rick,  KL7CW Palmer, Alaska    where things are still  all quiet on the western front
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VK2LEE
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Posts: 19


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« Reply #6 on: September 28, 2014, 07:47:05 PM »

I had an RFI problem (trashing the AM broadcast band) with a Toshiba laptop ps, but I plugged it into a line EMI filter from Cornell Dubiler, nf-10869-389 and that quieted it down.  It's a 3 prong metal box with all the filter inside.

Hi
I am using about 8 of different types of of noise Filters in My house at present. My AM radio was being wiped out with the switch mode power supply/car battery charger I use, and a MONSTER brand of plug in filter fixed that problem and I have a metal one attached to the battery charger [in a plastic box] and it helped.

I am now using a Toshiba Laptop Power supply with 6 torriods/chokes wound onto the power lead and now I have no noise from this at all.  It wasn't anywhere near the noise from the non genuine brand of power supply though.

cheers

Lee   VK2LEE

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28 years as VK2LEE - The 1st 3 letter L call ever issued - in 1986 -
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