General electrical question, figured this might be the best place to post...

[savage1987]

Whilst not strictly Commodore related (at all), I need help on a small interference issue. I am using an 'aftermarket' (I guess you could call it that) power cord on a laptop as the original one was destroyed by my dogs.. and now I get major interference when it's plugged in. Anything I can do about this? Speakers constantly whine, muted or not, headphones and external stereo gear do the same. Also ruins reception on certain TV channels on the household TV. I bought this off ebay under the impression it was designed to suit these laptops, should I be complaining? No chance of getting money back I imagine as it was sourced from Hong Kong. Couldn't find an original cord at the time.

So yeah, what do I do about this?? I have no idea.
Sam

[bezz]

i would be guessing but i would say it would be increased electromagnetic interference caused by the dodgy stepdown transformer on your power supply. You could try a powerboard with EMI mains filtration on it, however I don't know how much difference it will make. Jackson make them, can be found at your local dickies.

[savage1987]

hmm. Might be worth a go..
I know it's the power supply because when I unplug it the audio interference stops immediately, and with the old one I never had this problem.

[bezz]

having an emi filtered powerboard wont do anything for your audio interference unfortunately, but its possible it could stop the interference on your tv.

honestly tho man if i was you id be looking for another power cable.

[kopper69]

Just to check a few things. On the power supply does it say that it is rated for 240V 50Hz. It will probably say something like 90-250V 35-60Hz. Just to make sure that 240V is within range. Also, quick test. With the power supply connected and turned on, but NOT plugged into the laptop - does it still interfere with the tv etc? When you purchased the power supply, what made you think that it was for your laptop? Did the seller say or you just matched the voltage? What is the current output of the power supply?

[savage1987]

Test 1: Input 100-240V 50-60Hz
Test 2: No audio or TV interference with the power cord on but unplugged from laptop.

Seller had Toshiba Satellite (with my laptop model) listed as one of the supported laptops for the power cord.

Output: DC 19V 3.42A


Sound OK?
Sam

[bezz]

yep that all sounds ok, you wouldn't get any real noticable interference on your tv/audio with no load on the transformer, as all that would be running through it would be a bit of residual current attributing to losses on the transformer itself. Once connected the laptop however, much more current travels through, resulting in said interference increasing significantly. Apart from the powerboard I mentioned above (which will only help with interference on other devices, not your laptop itself), I don't think there's really much you can do. Look at getting your money back for it if you can, or maybe pressuring them to send you a replacement?

[kopper69]

Im no expert in noise, its a tricky field, but lets try a few things. Thanks for doing those above tests too.

OK. Its cheap and easy so give this a go. Get some cooking foil and wrap around the power supply, heck if you have enough wrap some around the wire between the laptop and power supply too. The idea is to create a Faraday cage Faraday cage - Wikipedia, the free encyclopedia that shields this noise. I would be surprised if it worked, not a solution if it did, but we could work something out.

The other thing I wanted to ask was - out of the power supply you have the cable going to the laptop. Does this have a cable ferrite?

(This is an cable ferrite).

These are based on a similar principle. Did your old power supply (if you can remember) have a cable ferrite? You can purchase clip on ferrites

.

Jaycar sell them for about $10, few different types. Just go to jaycars website and search 'ferrite'. Again, may or may not help. Plenty of info on the net about them, good page here:

Filtering Out Interference Signals with Cable Ferrites

Does the mains cord going into the power supply have 2 pins or 3 pins on the mains plug that plugs into the wall? Im going to guess that it has 3 prongs, which means it is using the earth. If this is the case, let me know. This is probably a very likely cause of your noise, with the problem fixed by simply using a travel adaptor that looses the earth pin. Can be dangerous, but we can discuss this if you do have a 3 prong mains cable.

[bezz]

OK. Its cheap and easy so give this a go. Get some cooking foil and wrap around the power supply, heck if you have enough wrap some around the wire between the laptop and power supply too. The idea is to create a Faraday cage Faraday cage - Wikipedia, the free encyclopedia that shields this noise. I would be surprised if it worked, not a solution if it did, but we could work something out.

haha nice, sort of the bush mechanics solution hey! be interested to see if it works

[savage1987]

The old one had a ferrite, the new one does too. I will test out that foil trick a little later.

Thanks so much for your help guys, I have no clue about this stuff. We were only just starting electronics in University when I chose a different path

Power supply has an earth pin, the old one didn't.

Sam

[vztrt]

What your getting is what is called EMF (electromagnetic feedback) this thing is obviously imported as its not up to Australian standards.

The ferrite actually could be a way of solving it as if one of the ends of the cable doesn't have the correct termination (by that its actually the correct resistance) you'll start having stray waves going here and there (this is very critical in communication systems).

[bezz]

What your getting is what is called EMF (electromagnetic feedback) this thing is obviously imported as its not up to Australian standards.

The ferrite actually could be a way of solving it as if one of the ends of the cable doesn't have the correct termination (by that its actually the correct resistance) you'll start having stray waves going here and there (this is very critical in communication systems).

thats the one... emf, rfi.. too many acronyms!

[savage1987]

That's probably it, cheap imported crap. Couldn't find a genuine one, might have to look harder this time!

[bezz]

targus make a good replacement power supply, unfortunately you have to be willing to part with $100...
Home/Office 90 Watt AC Notebook Power Adaptor
That's the 90w model, but im fair sure its regulated so you should be good to go...

[kopper69]

Ah ha!!! Your problem is that earth pin, I would put my money on it.

vztrt, you sound like your in communications? Not sure your answer was correct in regards to the power supply. EMF normally stands for ElectroMagnetic Field too in the electronics business, although I am aware of electromagnetic feedback, which is heavily tied in with the communications side of things.

OK, back to the problem. You dont need a new power supply or spend a lot of money. Your problem is the earth pin on your plug. Solution to fix your problems will cost you about $5, or maybe even free depending which option you choose.

I will sit down at work today and detail your options when I have a bit more time.

[kopper69]

OK. It sounds as if you know about the earth pin and which pin it is. There are a couple of options but I will list the two that are cheapest and easiest and will solve your problem. The manufacturer has included an earth pin. Why would they do this? Usually it is a requirement for safety. In the event of a fault, the earth pin will short the equipment out and blow a fuse or trip the breaker which may save your life. You might then wonder why some equipment doesn’t have this earth pin. In this case the equipment is regarded as double insulated. It should not have any exposed metal parts. Your power supply, does it have labeled on it anywhere:

The words “Class two” or a small picture of a square inside a square

It probably doesn’t, but let us know.

I will put my disclaimer in here to cover myself and say that you should never alter electrical equipment unless you are fully aware of what you are doing, why you are doing it and what the potential risks are. Anything that you do is your responsibility. I am going to list a procedure that will hopefully fix your problem. I am not directing you to do it and if you choose to do it you acknowledge that you understand what you are doing and are taking full responsibility.

Before doing anything. Your power supply – Is it all plastic? It should be. If not stop now. If it is a normal plastic case, and you cannot see any exposed metal read on.

Your first option is to purchase a travel adaptor. I don’t know what these things sell for, but I would imagine a couple of dollars at a cheapie shop. What these will normally do is loose the earth pin. You have to make sure that it has an Australian plug in and out and the earth pin is not passed through. This may not be easy to find.

Your best option and my preferred choice would be to grab a hacksaw or chunky pair of wire cutters and cut the earth pin off. Take a file and file it down level with the plug. Make sure that you cut only the earth pin (make sure you know exactly which pin is earth), don’t damage the other pins and don’t damage the mains cable.

This gets rid of the earth, costs nothing and will hopefully solve your problem. Let me know if you are after any more info or want anything clarified. I don’t recommend this for anything other than a fully plastic power supply used for laptops.

I have heard of this before and heard stories about people who have problems with their laptops, purchase a new laptop only to have the same problem.

Actually I just did a bit of searching around Google and found this:

Why am I getting power supply interference?

Same problem as you have described and looks like they use the same fix. There is a bit of crap in there, so dont take everything they say as fact.

Let me know how it goes.

[savage1987]

No 'Class 2' or little square diagram. No external metal either, just looks like your normal plastic laptop power cord. I know enough about electrics to know you can hurt yourself doing stupid stuff, don't worry about any more disclaimers unless you want to put them in for other people who might read the thread, unlikely as that is!

Thanks for your help, maybe I'll get brave enough to cut that earth pin off. Seems more practical than an adapter. So.. nothing bad will happen to the supply without that earth, it'll still function perfectly normally? I'm guessing it's only there as a precaution, i.e. doing nothing but as soon as you fry yourself by maybe sticking a knife in the power supply it kicks in and grounds everything? So because I'm never going to fry myself with my power supply I'll never need to worry about that particular annoyingly noisy precaution so the earth pin can go

btw sounds dumb but I just have to double check, the earth pin is the long one at the bottom right?

/ \
.|

Sam

[savage1987]

hmm, this is from the dude who had the same problem on that other forum...
Just letting you know that I have now fixed the problem!, I just bought a new laptop power pack (one of the generic ones without an earth and the option to change rates and connection plugs etc....), and it works a treat. After all the other options this is what worked for me, although admittedly I didn't try removing the earth pin. But the new pack doesn't have one so that's that problem solved, and it runs noticeably cooler too. So yeah, if you are a bit hesitant about removing the earth (I seem to get mixed messages about the safety), just get a earth-less new laptop power pack. Not that expensive. I think mine is a 6A rating, hence the coolness.

Any merit in what he said about it running hot? I don't understand why some get hell hot and some don't. Not that it matters but just out of interest, would mine possibly change operating temperature by removing that pin? I'm 99% sure you'll say no.

Sam

[kopper69]

Quick replies mate. Yeah, as mentioned earth is only there as a backup safety feature. It shouldnt be used for operation in any way. Earth is usually the longest and is down the bottom. When you said you knew which pin was the earth pin I assumed you knew a bit, disclaimer is just in there incase anyone else is reading and wants to give this a go. Power supply wont run any cooler. Its the design that will ultimatly decided how hot a power supply will run. Some components in the power supply work hard, they get hot. Cheaper power supplies will usually have smaller heatsinks to save $, but the smaller heatsink will run hotter. Cheaper power supplies also use a single part to do the work where a better designed but more expensive power supply will use mulitple parts working together to reduce the work load and share the heat - Two power supplies may produce the same amount of heat, but where one has it concentrated the other may spread it around a lot more. Unfortunatly, as you guessed, has nothing to do with the earth.

In the post that guy mentions that his power supply is rated for 6A. If his laptop is only using 3A its really only working 1/2 capacity and will run a lot cooler. Downside is the cost. If you are concerned about the heat, keep an eye on the power supply. Just feel with your hand every now and again and if it runs fairly hot for a lot of the time I would be thinking about replacing it. Just because it does present a bit of a fire risk running too hot and its lifespan will be reduced because of the temperature that it is running at anyway.

And yes, as long as you never go sticking anything into the power supply while it is turned on (hope thats a given) there shouldnt be any need for the earth. If you ever drop it and break it so that the case does not protect the guts, throw it out too. That should apply regardless of if it was earthed or not.

[savage1987]

Yep common sense really on that last bit.

None of the power supplies in the house run particularly hot, I was just curious. Thanks heaps for your help mate I'm off to rip that pin out now.


Sam

[savage1987]

hmm. I don't understand. Earth pin is gone but noise is still there, with the 5.1 plugged in anyway.
With the laptop by itself, the speakers used to have a nasty high-pitched buzz to them whenever the power was plugged in, now at least that noise is gone.

Here's the deal now:

Logitech 5.1 surround, X530 system
Plugged in to laptop

5.1 Any volume, laptop power supply disconnected: perfect sound
5.1 Low volume, laptop power supply connected: bad noise
5.1 High volume, laptop power supply connected: noise reduced until not noticeable.

So the way I need to set it up to be more or less noise free is:
laptop volume very low
5.1 volume very high


I am so confused.
Sam

[kopper69]

Double post

[kopper69]

Hey Sam,

Bad news about the speakers then. Nevermind, we will keep working on it. I am in search of an answer and tried googleing "X530 interference". Theres a fair bit about them and it seems as if they are particularly sensitive. There are even people out there who are saying that their X530's are picking up voices that sound like radio/shortwave/longwave transmissions.

Logitech speaker random clicking sound - Audio - PC Hardware

Logitech X-530 Speaker Weird Interference - Web Hosting Talk - The largest, most influential web hosting community on the Internet

Will keep trying for you. Do you have another pair of old speakers that you could try?

Thats a pretty big setup for a laptop too

[savage1987]

I do have another set of speakers I can try it with, will get onto that ASAP.

As for the sound system, my other laptop ran it just fine (Compaq Presario 2800 from back in 2000!) until the hard drive went slowly to its grave about 4 months ago. I'll repair it one of these days, it's the best computer ever.

I like my surround sound system but I feel bad having it turned so high so the interference goes away. Noise at low volume settings, how weird is that!?

Sam

[vztrt]

vztrt, you sound like your in communications? Not sure your answer was correct in regards to the power supply. EMF normally stands for ElectroMagnetic Field too in the electronics business, although I am aware of electromagnetic feedback, which is heavily tied in with the communications side of things.

Actually EMF is now apart of all electronics design as its a australian design requirement, if an electronic design is giving feed back then it should not be here. But there are seven ways of actually fixing it (I cant remember them as its been about 3 and a bit years since I touched on this subject).

Oh as for being in comms, I'm an electronic engineer (majoring in comms) by degree, but now I'm in singapore training up to be a district rep for Caterpillar.

If I was back in melb, I could do some reaserch and work out the link with single phase power as what i was talking about earlier is something that occurs with oscillating frequencies.