How to deal with a "noisy" room

Or perhaps there's magnetic aggregate in the concrete.

Aggregate is basically just crushed stone, dug out of wherever it can be found locally. If it was pulled out of a place with a high concentration of magnetite or hematite in the ground, that stuff is going to be in the walls.

Rebar is steel, so it's a ferromagnetic material, meaning it will be attracted to magnets. But in order for it to become magnetized, something would have to magnetize it. I don't know how magnetized it can become from the Earth's field alone. This isn't a problem we tend to see in a lot of other people's basements here, so I'd be more likely to think it wasn't the rebar itself. But who knows.

But yeah, it would be interesting to see what a field detector says, if you probed around your basement. But fixing the degauss circuits is probably the best thing you can do. Then put the games in their spots, and power cycle the games a few times a day. The degauss circuits take ten minutes or so to cool down before they will fire again, so it takes multiple power cycles spread out over time, for them to neutralize stronger fields. But you should see any monitor artifacts slowly disappear over a week or so, if the circuits are working.

So I'm swaying a bit from the OP's original question, but still somewhat related...

The company I work for installs magnetically-sensitive equipment in assembly plants. Before we do the installation, we do a magnetic survey of the concrete floors, and just as Andy says, we find areas with magnetic anomalies due to the aggregate or other hidden/buried utilities. We have specialized equipment to demagnetize these areas, and usually all is good. Post install, we do a final survey to ensure the floor magnetic properties are below our required threshold.

However, we did have an instance of a very confounding install where we would demagnetize the floor, all would seem to be good, and a few months later, issues would arise with too much magnetism in the floor again.

As it were, the floor in this plant was an all new, steel reinforced fiber concrete pour. So, we found out who poured the floor, and went to their plant for a visit to see their operation.

Guess how they added the steel fibers to the concrete mix? Giant electromagnets. Hmm, yeah.

So we came up with a remediation for that (company proprietary, so I can't say how), and have not had a problem at that plant for the last 20 years now.


Sorry Patrick, can't help with your problem, but it seems you have found a work around. :)
 
So I'm swaying a bit from the OP's original question, but still somewhat related...

The company I work for installs magnetically-sensitive equipment in assembly plants. Before we do the installation, we do a magnetic survey of the concrete floors, and just as Andy says, we find areas with magnetic anomalies due to the aggregate or other hidden/buried utilities. We have specialized equipment to demagnetize these areas, and usually all is good. Post install, we do a final survey to ensure the floor magnetic properties are below our required threshold.

However, we did have an instance of a very confounding install where we would demagnetize the floor, all would seem to be good, and a few months later, issues would arise with too much magnetism in the floor again.

As it were, the floor in this plant was an all new, steel reinforced fiber concrete pour. So, we found out who poured the floor, and went to their plant for a visit to see their operation.

Guess how they added the steel fibers to the concrete mix? Giant electromagnets. Hmm, yeah.

So we came up with a remediation for that (company proprietary, so I can't say how), and have not had a problem at that plant for the last 20 years now.


Sorry Patrick, can't help with your problem, but it seems you have found a work around. :)


I'd say that's pretty related!

Thanks for posting.
 
I have degaussing wand. How could you run an arcade without one?

The wand and the coil are two different animals. The coil will affect the screen from about 4' away. It'll also demagnetize the monitor frames if needed. I use mine to demagnatize all kinds of stuff. Its really powerful. I'd bet you could move the games away, and use the coil (not the wand) and demagnatize whatever is causing your issues, even through the concrete.
 
Sorry, I was calling the 13" inch coil from APAR a wand. I just looked on Amazon and there are cheesy little degaussing "wands" you can purchase. I see the confusion I caused.
 
So I'm swaying a bit from the OP's original question, but still somewhat related...

The company I work for installs magnetically-sensitive equipment in assembly plants. Before we do the installation, we do a magnetic survey of the concrete floors, and just as Andy says, we find areas with magnetic anomalies due to the aggregate or other hidden/buried utilities. We have specialized equipment to demagnetize these areas, and usually all is good. Post install, we do a final survey to ensure the floor magnetic properties are below our required threshold.

However, we did have an instance of a very confounding install where we would demagnetize the floor, all would seem to be good, and a few months later, issues would arise with too much magnetism in the floor again.

As it were, the floor in this plant was an all new, steel reinforced fiber concrete pour. So, we found out who poured the floor, and went to their plant for a visit to see their operation.

Guess how they added the steel fibers to the concrete mix? Giant electromagnets. Hmm, yeah.

So we came up with a remediation for that (company proprietary, so I can't say how), and have not had a problem at that plant for the last 20 years now.


Sorry Patrick, can't help with your problem, but it seems you have found a work around. :)
Magnets. They are everywhere.

Long story - I had just got back to LaSalle after spending 2 years at Dresden. We had installed the GE Mark VI Digital Turbine Control System to remove the obsolete Mark I system.

The new system was triple-redundant for EVERYTHING (unlike the Mark I which had no redundancy) including speed signals.

Also, the Unit 1 Turbine speed was always off - it would read 1745 rpm, not 1800 or so. It was because the "toothed wheel" in the front standard (which uses a Hall sensor to sense tooth passing, and thus determine speed) had a chipped tooth. The decision was made to replace the "toothed wheel" to correct the speed while we had the unit torn apart.

When we started up, we "rolled" the turbine. That's when you admit steam to the turbine to make it spin. When it got to nearly 1800 rpm, the speed indication went snaky. We checked, and all three speed signals were messed up - would not be read at 1800 rpm. So we couldn't synchronize the generator to the grid.

We got on the phone with the OEM, and after working with them for a few days, one of our engineers said "I'll bet the toothed wheel is magnetized, so we're inducing a signal on the speed sensors."

We installed 1K resistors across each speed signal, and that attenuated the induced signal and we were able to synchronize the generator to the grid, and start power ascension.

24 months later, we checked and yep, the toothed wheel was magnetized. That was the root cause of the problem that kept me on night shift for a week.
 
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