Lamp fixture causing RFI?

[AdmiralB]

I ran a pigtail from the earth of one of the room's outlets to the fixture chassis - it had no effect on the noise, as I pretty much figured.

I also checked the wiring of the outlet I used, just to be sure, and it's fine.

[Steve A.]

I've considered the grounding issue. I've verified that it's wired as such (which isn't easy since its power is taken from the fan), but not that the box itself is proper. As suggested, it's easy enough to do a continuity test with an outlet, though.

But what effect would grounding really have on a lamp socket? All it will prove is that the base of the fixture is connected to earth. The sockets themselves have no earth connection, there is no 'shielding effect' of a chassis. From a theoretical perspective I can't imagine why the lack of a ground would really matter.

I was thinking more of an improper ground... in old houses the neutrals and grounds can get interconnected by wannabee DIY electricians. Thanks for checking it despite your reservations.

In the mid-80's I was an in-house service tech for several home warranty companies and had to deal professionally with appliances, wiring, plumbing and HVAC (that was before I decided to specialize in HVAC.)

There was this GE self-clean oven that had an obvious problem with temperature control as the indicator light and heating element would cycle on and off every second or two- this even after I replaced first the sensor and then the temperature control board.

After several calls to GE technical support something clicked in one of the old-timer's head and he remembered an ancient technical service bulletin and asked: "Is there a dimmer switch nearby?"
"Yes there is."
"Try reversing the two incoming 240VAC power leads in the oven and call us back if it doesn't solve the problem."

Well, that certainly solved the problem and after that day I was a firm believer that God- and electricity!- work in mysterious ways...

Another story... a few years before that I was maintenance man at an apartment complex that was being converted into condos. I was checking the GE self-clean range in a vacant unit and when I turned on a burner the ceiling light dimmed. "WTF is going on?!?"

It turns out that the electric company had put insulating sleeves on the prongs of the meter which plugged into the meter base and there was enough leakage current to turn on a light bulb or two but not an element on the range...

Steve Ahola

P.S. For the heck of it check if the rooms are on different circuit breakers, and if they are then check to see if they are on the same 240VAC leg. Depending on the breaker panel you can determine that by the location of the breakers. Or you can run an extension cord from one room to the other and see if you are getting 240VAC or 0VAC between the two hot leads.

If the two circuits are on different legs of the 240VAC I would switch wires in the breaker panel so that the bedroom is now on the same circuit as your old music room. (There could be something connected to the 240VAC leg your bedroom is on that is causing interference picked up and rebroadcast by the LCD & LED lights in your bedroom.) BTW the bedroom outlets and fan might be on different circuits...

[Steve A.]

Hi Steve!

I did think of that, but it did this before I moved (I forgot to mention that); when my stuff was in the 'music room', if I walked into the bedroom with a guitar (again, wireless), it'd go nuts with noise. I've verified that those two rooms are on different circuits.

I must have skipped over this post... and others, too. My bad! So are you getting the same noise when plugged directly into your guitar amp?

Steve Ahola

[AdmiralB]

I must have skipped over this post... and others, too. My bad! So are you getting the same noise when plugged directly into your guitar amp?

Yeah, same problem whether wireless or using a cable.

[J M Fahey]

You can make a Buzz Sniffer wiring a single coil pickup , any leftover one sitting on a drawer,to a battery powered amp, something as simple as an LM386 driving a couple headphones and move around searching for interference source.

You may even tape it to the end of a broomstick or similar to reach near the ceiling.

Once you found the *real* source, then you can start worrying about what to do to stop it ... if possible.

I bet you already have everything needed for it .

[olddawg]

Have you run a 3 extension cord from the "good" room? If it stops it's a wiring issue. Could be ungrounded or reversed. IMHE, usually any triac dimmers will radiate into single coils.

[AdmiralB]

The problem is the light, not the power source for my amp - as I mentioned elsewhere, when my rig was in the 'good' room, this would happen if I walked into the bedroom with a guitar.

Unless I misunderstand what you're suggesting, and you mean power for the lamp itself - which isn't really practical to test since it's part of a ceiling fan.

[AdmiralB]

Pretty sure this is the *real* source, since changing bulbs to incandescent fixes it.

[olddawg]

Pretty sure this is the *real* source, since changing bulbs to incandescent fixes it.

Well... You said the fixtures were the same in both rooms. Noise can radiate into the ground if it is floating and get into your signal that way. That's why I said try an extension cord from the other room. Also if it's radiating into a single coil it should typically vary in intensity as you turn 360 degrees.

[J M Fahey]

It has been established long ago that interference is electromagnetic, radiates from the lamps and gets into your guitar pickups, donīt undestand why this thread keeps rolling on and on.

[AdmiralB]

The weird thing in all of this is...it radiates into everything - single, humbucker, EMG, etc.

[olddawg]

If the lamps are the same, with the same bulbs, and one radiates and one doesn't I still suspect the lamp chassis or the fixture is not properly grounded. What I would do is run a 3 wire extension cord from the "good" room. Then run a continuity test from the lamp body (assuming it is metal) or whatever part of it should be earth to the ground on the extension cord. If it is not continuity you have a wiring issue. Even if the other room is on the same circuit breaker it should have the same earth. If that shield or ground plane is missing in the offending lamp it can radiate much more.

[AdmiralB]

If the lamps are the same, with the same bulbs, and one radiates and one doesn't I still suspect the lamp chassis or the fixture is not properly grounded. What I would do is run a 3 wire extension cord from the "good" room. Then run a continuity test from the lamp body (assuming it is metal) or whatever part of it should be earth to the ground on the extension cord. If it is not continuity you have a wiring issue. Even if the other room is on the same circuit breaker it should have the same earth. If that shield or ground plane is missing in the offending lamp it can radiate much more.

As I mentioned in the reply to Steve yesterday, I did that - no effect.

I can't see how it would have made any difference. There is no metal between the bulbs and me (if there was, there would be little point in turning it on, eh?), so there's no shielding effect.

I'm now at the point in thinking there's something on the AC going to the bulbs, though I can't imagine what. Next step is to 'scope it.

[AdmiralB]

It has been established long ago that interference is electromagnetic, radiates from the lamps and gets into your guitar pickups, donīt undestand why this thread keeps rolling on and on.

I assume it keeps rolling because it's a mystery that's not solved?

Yesterday I took the bulbs out of the fixture, put them in a table lamp, and stood less than a foot from it. No interference.

Which tells me it's not the bulbs, and not the fixture, but the combination of the two.

[Tom Phillips]

Given all that has been said and tried how about the following as a next step?
Set up the conditions with the fixtures and bulbs that make one room bad and the other room good.
Then swap the complete fixture and associated bulb assemblies between rooms and tell us if the problem moves with the fixture or stays with the room.