Demagnetizer mishaps

Hi all,
I very absentmindedly demagnetized the heads of my MX70 1"8-track with a han-d-mag while the tape machine was still powered up.
I haven't noticed anything out of the ordinary after this mishap. I've read several dire warnings in the past that this sort of boneheaded mistake can permanently, irreversibly magnetize your heads. Is there any specific type of noise I should listen for that might let me know if the heads are indeed magnetized?
Has anyone else here ever made the same mistake?

not familiar with the concept of that magnetizing the heads,
just that wailing that much signal into the electronics is...well,
imagine the strength of  the magnetic particles on tape, those very tiny little
magnets are as small as they can make and still have them hold magnetic charge
(smaller particles = lower noise).

now imagine the strength of your degausser (electromagnet), which you can pick up a nail with...
and the signal it is putting out - 50 or 60Hz nasty huge kinda sine wave lookin' things!
stick that up to the heads, and whoa!

the sound of the meters whacking madly against the pegs should alert you that
something is goin' on.

meters ok?  does it align ok?  does it erase ok?

ok

Hey that's a good point. The VU meters didn't so much as budge while I was demag'ing--i believe a relay mutes things when the machine is stopped unless you click the cue button. Also, what you said makes a lot of sense--that the extreme level would be the problem here. The meters are OK. It seemed to align OK and erase OK.

Being switched on has NOTHING to do with magnetization. -If you understand how it works, you'd know this immediately.

But...

Switching the demagger on or off while ANYWHERE NEAR any piece of ferric material -whether it's a recording head, a playback head, a paper clip or a battleship- WILL magnetize whatever is close to it.

I may be re-stating what you know, but it's not clear whether or not you DO know.

A demagnetizer doesn't know or care if it's on or off, nor whether it's a tape machine or a washing machine.

Keith

Thanks Keith,
I did already understand that turning the demagnetizer itself on-or-off while close to the heads will magnetize them. I've experimented a bit with magnetizing/demagnetizing screwdrivers. This paper (http://home.comcast.net/~mrltapes/mcknight_demag.pdf) found the 'safe distance' for turning the demagger on/off to be about 70 mm from the heads--manufacturers seem to recommend keeping a wayyy greater distance in the manuals I've read (CYA?).

But in terms of the tape machine itself being on while de-magging, sounds like i was misinformed about this being a recipe for permanently magnetized heads, right?

But what Queef Bag said makes me wonder if someone, hypothetically, de-magged a machine that doesn't mute the heads while stopped, would it generate a powerful enough 60hz signal to damage stuff downstream? 

It might bend the needles of the VU meters, or destroy any headphones or speakers which are unfortunate enough to be fed signal from the output...

But other than that, not much.

Only demag mistake i ever made was having my wallet in my pocet as I demagged a machine once... as u may have guessed all magnetic strip cards like my bank card and credit card got erased. Not fun...

awesome, thanks for clearing that up Keith.

And Pucho, I did the same damn thing last year with a public transit card in my pocket. Not to relish your misfortune--but I'm glad I'm not only who's ever made that mistake ;D !