Thomas
Dave
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:Yep! Place a .1 MFD condenser (250 WVDC found at Radio Shack) across the dimmer's leads. If that doesn't work, place a 100 mH choke (also found at Radio Shack) on each lead of the dimmer. Also, along with the chokes, try placing a .1 MFD condenser across the dimmer leads on the dimmer side of the chokes, and also one on the wiring side of the chokes. Try with one, the other, and then both. Do not place condensers across each choke, as this will nullify their action.
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:Thomas
Generally you locate the source of the noise and use components between the noisy device and the line. Components inside the chassis may reduce the noise if it is entering the radio from the power line. However, if the noise is being radiated from the AC wiring in the house into the antenna of the radio, then adding filtering in the radio probably wont help. You may try using a portable transistor radio to try to determine if the noise is being transmitted thru the AC wiring to the radio or being radiated from the AC wiring.
Radiodoc
:Can I take care of the filtration inside my chassis. I was thinking about adding a couple of inductors in series with the ac lines and then a .1mfd in parallel.
Thomas
What everyone else says is very true. My recommending 250 volt regular condensers isn't the greatest idea, though I've seen many old radios with 200 volt line condensers. I have also used the 250 volt blue .1 MFD condensers from Radio Shack quite successfully in both radios and dimmers. It isn't the greatest idea, though. It's best to use one of those safety condensers rated for at least 400 volts, if not 600.
Regarding putting the chokes in your radio, this will work well. It may even be necessary if there isn't enough room in the switch box. However, like everyone says, catching the noise at its source is the best. Also, if you place the chokes on the line of the radio, you'll reduce the radio's reception capability. If it's an AC radio, all you have to do is make an alternate ground to a water or radiator pipe. If it's an AC/DC set, though, you can't do that. If you must put the chokes inside of your radio, put one on each side of the line cord. Wire a condenser of the type mentioned above (preferrably a safety cap.) across the radio side of the chokes. You can also wire one across the AC cord side if you wish, but this might increase interference. Try one on each side and then one on both sides, and see which way works the best. You can also try putting a choke on only one side of the line cord (the hot side, which is normally the side not switched in old radios). I have found that in some cases this works fairly well as long as you plug in the radio with this side in the small hole of the outlet (the hot side of the outlet). Connect a condenser across from the radio side of the choke to the other side of the line cord. Also try one on the line cord side of the choke to the other side of the line cord. Try both. Sometimes one way works better than the others. I have most often had the least success with condensers on both sides of the choke(s).
Another thing I have seen with the double chokes method is to connect two condensers in series on each side of the chokes, and then connect their junction points to the chassis. Again, try two on one side of the chokes, then on the other, and finally on both sides (4 condensers total).
Finally, if you can't fit the chokes inside of the switch box, or they won't work for the load you have, put them inside of the radio, but still put a .1 MFD safety condenser across the leads of the dimmer. If you want, pull the dimmer out of the wall and remove the wire nuts from its leads. Turn on the fuse after separating the wires so that they can't touch eachother or the box. Carefully, with one hand, turn on the dimmer so that the light lights. Turn on your radio. Listen to the static. Then carefully touch a .1 MFD safety condenser across the dimmer leads and see if this helps things.
Thomas
The .005 MFD condenser from the AC cord to the chassis is not absolutely necessary. There is also some capacitive coupling through the power transformer, though not as much as through the condenser. The condenser will improve reception somewhat, as will connecting the chassis to an alternate source of ground.
What you should do to minimize interference, aside from the choke ideas I gave you, is connect a condenser from one AC leg to the other in your radio. Do this on the radio side of the switch. The condenser that goes from the AC cord to the chassis is not there to reduce interference, contrary to what some misinformed individuals will tell you.
Regarding shock hazards with condensers tied to the chassis, all you need to do is keep your fingers off of sources of ground and you won't get shocked. Even if you omit the condenser, there is still capacitive coupling through the power transformer, and the slight chance for shock, especially if your fingers are wet. Leave the radio the way it is. It is designed well. If you wish to add filtering devices such as those I mentioned, do so. Don't modify the radio just so that you don't get shocks from the chassis. All you have to do is use your head and then you won't get shocks from the chassis. You can also get shocks from your television and VCR if you touch the RF cable jack and a ground source at the same time, etc. Don't do that and you won't get shocked.
Thomas
Use a polarized line cord and put the power switch on on the hot leg (the one with a narrow blade on the AC plug). Then you will not measure a voltage with the power switch OFF.
I would replace the line-to-chassis cap with a UL safety cap. Place the cap on the radio-side of the power switch.
::The radio originally used a .005 cap from one leg(before the power switch) to ground. Scheamtic shows that. BAD idea! I found that that the voltage winds up charging the power transformer and there is voltage in the chassis when the power switch is off. Its a "fake" 30vac but never the less it's there. I tried the caps from the a/c line to gnd and it made things worse, can you believe that. I was thinking about using a MOV in parallel with the dimmer and see if that works. Why would chokes in the power line kill my incoming radio signal?
If you wish to leave the wiring in its conventional form, put the condenser on the switch side either before or after the switch. Putting it before the switch is wisest if you always plug the radio in with the switch on the cold side, for if it's on the radio side of the switch, it'll become hot when the switch is turned off. I really don't think that all of this is as important as some people make it out to be. It makes me think of times when people think up stuff when they have nothing else to think up. Just keep your hands off of a source of ground while working on the chassis and you'll be just fine.
Thomas
I think I'm going to go to sleep now. Too much to explain. Not enough brain power left to explain it. I don't know where people get these wild misconceptions about ground and such, and I wish that the chassis in a radio would never ever be referred to as ground again. It isn't ground. It is simply a large metal object that's used as a big wire. If it wasn't connected to anything at all, it would simply be a metal box.
I don't care anymore, though. It's like the blind leading the blind, and I'm the fool on the hill that noone listens to.
Good night.
Did you replace the .005 cap? For safety, it would probably be a good idea. One rated 630 volts or better or even a safety cap (believe safety cap was mentioned earlier).
Radiodoc
:You dont have to think of yourself as a fool. Listen to Radiodoc.
Ben M.,
I just wanted you to be safe. If it works better without it, leave it out. Could have been the manufacturer determined there was no improvement in operation and left it out of later models. There are some light dimmers that have built-in noise suppression. They are generally more expensive than the ones at the discount stores. Radio Shack used to sell a unit that was sealed in a metal block with ears for mounting. A nearby Radio Shack a few years back was closing and selling out and I purchased several of these at I believe a buck apiece. I used a few in some applications by mounting them in the bottom of a double metallic outlet box, wiring them in and mounting a couple of duplex (3-wire) outlets on the box with a cover and about a two-foot pigtail with a three-wire plug on the end. Worked pretty well. I still have one of the setups on the workbench of the shop.
Radiodoc
Ben M.,
In my post about the line filter, I forgot to mention the noise/interference was being transmitted thru the wiring and not being radiated from the wiring and was comming from outside and beyond my control.
Radiodoc
Thomas
Electricity.
1- A large conducting body, such as the earth or an electric circuit connected to the earth, used as an arbitrary zero of potential.
2- A conducting object, such as a wire, that is connected to such a position of zero potential.
Not a misconception but a fully understanding of electricity basics.
Z-
Truth is, the chassis isn't ground. The only thing that's ground is the ground itself. The only electrical thing that's ground electrically is anything that connects to the earth. Referring to every major common return or base plane as ground leads to conceptual confusion. I see it everywhere, and it just makes me want to smash my head against a wall. The only thing the chassis is is a common return of very large size. If, after you thoroughly understand how everything works, you want to refer to the chassis as ground, then do so, but keep it to yourself (you in general, not any specific person), because it confuses everyone else. People get this idea that because it's called a ground it has something magical about it. A CHASSIS AND THE EARTH ARE TWO ENTIRELY DIFFERENT THINGS. THEY ARE NOT AT ALL THE SAME. I capitalize for emphasis, not for shouting. They both can be used for a common return, but a chassis 'ground' is not at all the same as an earth 'ground'.
Now that I've had my rest, though, I once again have enough energy to properly explain everything without losing my mind. The chassis of your radio is not ground or earth. Let us never talk about ground again unless we're talking about a wire that actually goes to ground (earth). The condenser that goes from the chassis to the line cord is for a couple of reasons. For one it puts the chassis at the same AC potential as everything else in the room. This adds shielding and stability to the circuits. It keeps the chassis from picking up stray fields that might alter circuit performance. An ungrounded chassis might more likely cause the amplifier to hum, for instance. It might also allow oscillations to occur if the circuits can react with eachother through the chassis medium.
Also, the condenser between the chassis and earth affords better reception (my original key point that noone seems to understand). When radio waves eminate from the transmitter, they alternate back and forth through the antenna and earth. The planet Earth acts as the other side of the RF circuit. If you did not have Earth to connect to, you'd have to have another antenna on the other side of the transmitter output coil in order to complete the circuit (sort of like a balanced V doublet antenna, but not necessarily physically the same). Earth radiates, too. You could think of it as a return, but since radio waves are alternating current, they actually come out of both the antenna and the ground as they alternate back and forth. When you receive radio waves with a long wire, they go into the wire and through the antenna coil, and then into earth. They then reverse direction and go from earth to the antenna. They do this as many times as the frequency which you are tuned into. Battery radios will not work without a ground. Neither will crystal radios. The only reason why AC radios will is because there is also capacitive coupling through the power transformer. It is not enough to maximize ground coupling, though, so a condenser is often used to improve things, how ever minor the improvement may be. The condenser is connnected from the line cord to the chassis.
Battery radios with loop antennas work without grounds because they have a closed circuit. The radiation from the transmitter antenna and the earth induce currents in the antenna, which has its circuit closed by the tuning condenser. Still, both AC and battery radios with loop antennas can be improved by connecting them to an auxilary source of ground.
Now, to reduce radio interference from the line cord, a condenser is connected ACROSS THE AC CORD. The condenser that goes from the cord to the chassis is NOT for reduction of interference. It is more likely to pipe in more interference.
I know that most won't take the time to read this, though, and so they won't have any understanding as to what is going on, and so I'll see the same questions and misinformation over and over again.
Thomas
The line cord is not ground, you should be able to explain that in Layman's terms. I thought the definition I just posted would clarify things, seems not.
:Truth is, the chassis isn't ground.
The chassis IS ground unless it is entirely isolated from the circuit. Most radios I know do not have an isolated chassis, the chassis IS the ground, i.e. zero reference. Do you own a car ? What do you call the negative on the car's chassis ? GROUND !
Ground and earth ground are not the same thing.
Unless you wish to redefine electricity and all the definitions related to this science.
:The only thing that's ground is the ground itself. The only electrical thing that's ground electrically is anything that connects to the earth.
Nope. A ground does NOT have to be earthed. A ground is a common _reference_. Then, you can add an earth ground.
:If, after you thoroughly understand how everything works, you want to refer to the chassis as ground, then do so, but keep it to yourself
I do understand quite well the concept of electricity and electronics ? Do you have any technical background at all ? I read your posts and all you can do is generalize. I can't find any proper/correct terminology in any of your post. If you had taken _any_ technical course, you'd know all that.
What's that compulsion to always attack my post with personal comments and snide remarks since day one ?
:...because it confuses everyone else.
I doubt using proper terminology would/should confuse anyone.
: A CHASSIS AND THE EARTH ARE TWO ENTIRELY DIFFERENT THINGS.
We are talking about "ground", not "earth ground" so far. Please read on the subject in just about any good electrical or electronic books (I can suggest a few, Henney's comes to mind, simple to read) on the subject.
: but a chassis 'ground' is not at all the same as an earth 'ground'.
Now we agree. A chassis IS ground and earth is something different (usually called earth ground).
http://www.nostalgiaair.org/PagesByModel/368/M0025368.pdf
Here's an example: Look at page 3, far right, the little symbol..."Denotes Chassis Ground"...There is also a small cap (C21) going from one side of the line to the...chassis ground.
Kind regards,
Z-
: I am also concerned that the chassis has a potential on it due to the line caps as well as the fact that a lot of the radios had the power switch on the ground leg and putting the caps before the switch.
. PL
Also, typically, when electrical codes were followed, the wire with the tracer or rib (if rubber or plastic) was considered the "cold" wire, and was usually connected to the switched side of the radio. This wasn't always the case. I have seen literature where the tracer was established as the "hot" side. In most (if not all) of my radios the ribbed or tracer wire was connected to the switch, as well as the chassis condenser, if a chassis condenser is used. I have replaced most of the cords, so I can no longer use this as a reference except by memory.
Thomas