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How to tell if demagnetizer is working

D

Dual Teac

New Member
After reading the threads here on tape head demagnetizing I decided to pull out my old Radio Shack wand type demagnetizer. It has a light that is supposed to come on when you use it (to illuminate the tape heads) but it's not coming on. How can I tell if just the light is out or the whole thing is dead? I thought about running it over a cassette I didn't care about, but I don't think I'd want to then play the cassette in my Teac CX-400 deck to check if it had been ruined as I presume it would be.

Any ideas how to test it for functionality?

Also, does anyone have any experience with the cheapos on eBay such as:

http://tinyurl.com/2gfbt6 ?
 
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I haven't used mine (a cheap wand type) in ages and don't even know where it would be, but iirc I felt a slight vibration when putting the tip on ferromagnetic parts. So, if my memory doesn't fool me, you could just try yours for example on a couple of screwdriver blades and feel for the vibration. Another idea would be to hold it near (but not too near!) a compass needle and see whether it irritates that, when you switch it on/plug it in...

Greetings from Munich!

Manfred / lini
 
The Teac is made to vibrate as stated but mine is very quiet. Hold it to your ear to listen for the vibration. Or the other steps above.
 
Usually the only time you can tell when one is vibrating is when it is held next to a piece of ferrous metal.

If the heads on your deck are small it will be harder to tell if it is vibrating compared to the heads on a reel to reel which are bigger.
 
I would think if you could hold it up to the compass and the compass needle should swing wildly. That is providing you have a compass.
 
HI,
Of course, that may demag the compass!! But that will show it is working at the cost of a ruined compass.

Sparky
 
Karma16 said:
HI,
Of course, that may demag the compass!! But that will show it is working at the cost of a ruined compass.

Sparky
Click to expand...
I tried it on a compass. With the button on the demagnetizer pushed I slowly moved the wand towards the compass. The compass needle moved slightly towards the tip of the wand. I then tried it again, this time without pushing the button. The needle swung away about three times farther than it had previously swung towards the wand. I then unplugged the demagnetizer and tried it again. Whether the button was pushed or not, with no power supply the needle moved away about the same amount as it had with it plugged in, but the button not pushed. Sooo, I guess this means it's working.

Too bad that $100 dive compass now points southwest!

No, just kidding, the compass is fine! :D
 
Hang an oscilloscope across the leads going from a tape head back to the electronics. If the demagnetizer is working, it will induce a signal into the head which will then travel down the wires.

Fred
 
Fred Longworth said:
Hang an oscilloscope across the leads going from a tape head back to the electronics. If the demagnetizer is working, it will induce a signal into the head which will then travel down the wires.

Fred
Click to expand...

HI,
Fred, does everybody have a scope hanging around? I do. But not everybody. In fact, almost nobody. And, would you actually go to this much trouble? Often, it's not so easy to get to those leads especially if the recorder is not disassembled. Come on. Use your wonderful experience for a practical answer. This is a good and practical question that any average audiophile might have. We need a general answer that everybody can use.

Personally, I have found that putting the demagger in physical contact with steel will cause vibrations to be felt. But I'm not sure it will work with all units. Often, just putting the demagger up against the head pole pieces will also cause vibrations that can be felt. Sometimes you can actually hear the vibrations.

Sparky
 
Dual Teac said:
I tried it on a compass. With the button on the demagnetizer pushed I slowly moved the wand towards the compass. The compass needle moved slightly towards the tip of the wand. I then tried it again, this time without pushing the button. The needle swung away about three times farther than it had previously swung towards the wand. I then unplugged the demagnetizer and tried it again. Whether the button was pushed or not, with no power supply the needle moved away about the same amount as it had with it plugged in, but the button not pushed. Sooo, I guess this means it's working.
Click to expand...

That already sounds good to me. And did you also try my other suggestion, i.e. touching some ferromagnetic parts on which demagnetizing would surely do no harm (e.g. screwdriver blades, wifey's cast iron frying pan et cetera) with the wand tip and feel for vibration?

Oh, and yet another idea: Once again slow approach (like with the compass needle) - but this time to the screen of a tv set or monitor with conventional cathode ray tube: I'd expect an increasing reaction on image stability...

Greetings from Munich!

Manfred / lini
 
Dual Teac said:
I tried it on a compass. With the button on the demagnetizer pushed I slowly moved the wand towards the compass. The compass needle moved slightly towards the tip of the wand. I then tried it again, this time without pushing the button. The needle swung away about three times farther than it had previously swung towards the wand. I then unplugged the demagnetizer and tried it again. Whether the button was pushed or not, with no power supply the needle moved away about the same amount as it had with it plugged in, but the button not pushed. Sooo, I guess this means it's working.

Too bad that $100 dive compass now points southwest!

No, just kidding, the compass is fine! :D
Click to expand...

Oops I should have mentioned use a compass from a Crackerjack box. :D
 
lini said:
That already sounds good to me. And did you also try my other suggestion, i.e. touching some ferromagnetic parts on which demagnetizing would surely do no harm (e.g. screwdriver blades, wifey's cast iron frying pan et cetera) with the wand tip and feel for vibration?

Oh, and yet another idea: Once again slow approach (like with the compass needle) - but this time to the screen of a tv set or monitor with conventional cathode ray tube: I'd expect an increasing reaction on image stability...

Greetings from Munich!

Manfred / lini
Click to expand...
I tried it on a screwdriver but felt nothing. The instructions that came with the demagnetizer say do not touch the heads with it, so I don't remember ever touching it to metal back when it was new. But, based on the compass test, there is a magnetic field even with the unit off, so I'm unsure what putting it close to a TV screen would prove. I'm sure the TV screen would react to it. It might be interesting to see what the TV does with it on and with it off, if it doesn't wreck the screen.

Hmmm, don't CRTs degauss themselves whenever you turn them on, typically?
 
I have recently purchased the R.B. Annis Han D Mag. Now thats one heavy demagger. Supposed to be the best in the buisness. I was reading the directions on the box and it states: Clean the heads first with Anhydrous Alcohol, then to take Non waxed dental floss and clean the guides and tension guides. That was new to me on that cleaning trick. Then to plug the demagger in 3 ft away from a NON powered Deck and no tapes loaded within 3 ft of the deck, and slowly move in and get close to the heads. In a circular motion for 15-20 secs each. Starting left to right. But this is a powerful demagger. You put it in front of a paper clip to test you can feel it buzz the clip very hard. So thats some power. Just my 0.2 cents on it hehee :thmbsp:
 
TeacGuy said:
I have recently purchased the R.B. Annis Han D Mag. Now thats one heavy demagger.
Click to expand...
It would be interesting to see what that one would do to a compass. I have a feeling this RS one is very weak in comparison judging by the fact that I had to move it's tip right next to the compass to get any reaction.

If I get more "into" tape I think I'll invest in a Han D Mag.
 
Karma16 said:
HI,
Fred, does everybody have a scope hanging around? I do. But not everybody. In fact, almost nobody. And, would you actually go to this much trouble? Often, it's not so easy to get to those leads especially if the recorder is not disassembled. Come on. Use your wonderful experience for a practical answer. This is a good and practical question that any average audiophile might have. We need a general answer that everybody can use.

Personally, I have found that putting the demagger in physical contact with steel will cause vibrations to be felt. But I'm not sure it will work with all units. Often, just putting the demagger up against the head pole pieces will also cause vibrations that can be felt. Sometimes you can actually hear the vibrations.

Sparky
Click to expand...

That's funny - because the first thing I thought was, "wow - cool answer!". Probably because I have a 'scope but still don't really know how to use it, so this might be a good way to incorporate it into a simple project.:thmbsp:
 
longfade said:
That's funny - because the first thing I thought was, "wow - cool answer!". Probably because I have a 'scope but still don't really know how to use it, so this might be a good way to incorporate it into a simple project.:thmbsp:
Click to expand...

I thought the very same thing!
And my scope needs some learnin' too -- or is that me I'm thinking of ....

Thanks for the insightful post Fred.

Doggone those guys with cat avatars anyhow. :smoke:
 
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