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Author Topic: LAST Tape Preservative - First Try  (Read 19039 times)

Offline steveidosound

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Re: LAST Tape Preservative - First Try
« Reply #15 on: March 24, 2009, 09:02:13 PM »
I re-read that entire article again after I posted the link, and although it gives a lot of semi-technical info about the process it is somewhat light on specific procedure.
It seems that the whole idea has been somewhat over-dramatized  in tape recorder lore in that it has to be done a lot, and if you do it at all wrong you will make matters worse.
Jay's article seems to debunk some of the more commonly held myths.
As to exactly how I demagnetize (feel free to correct me here fellow Tape Project experts), I turn on the unit about 3 feet from the recorder, move in fairly rapidly and touch each metal part (heads, guides, capstan etc.) with the protected tip of the demagnetizer and move a few inches away fairly slowly at first, in a circular motion, then back in for the next part etc., NEVER turning off the demagnetizer near anything. When I have covered all pieces, I typically move back in fairly close to the center of the whole general headblock area without touching anything and then out again in increasing diameter circles as I had for each individual part, till I am about 3' away or however far I can reach and/or the cord will let me go before turning off the demagnetizer. The main thing is to not turn the demagnetizer power on and off close to the heads or other parts, and to get close enough to each part and not jerk the demagnetizer rapidly away at first from the part. As you get further away how smoothly you move becomes less critical. Of course you also don't want to actually scratch the heads with an unprotected metal tip.
Steve Williams

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Offline ironbut

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Re: LAST Tape Preservative - First Try
« Reply #16 on: March 24, 2009, 09:19:22 PM »
When I'm moving the demagnetizer to and from the machine, I remember what Duncan Idaho told Paul Atreides "It's the slow blade that penetrates the shield!". If you saw the movie of Dune, your movement should be kind of like that. When you get within a foot and a half or so, move in slow motion like there's a shield surrounding the heads. Then when you back out far enough, you can move normally. The only difference is that you have the energy field in your hand.
steve koto
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Offline steveidosound

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Re: LAST Tape Preservative - First Try
« Reply #17 on: March 24, 2009, 11:13:37 PM »
I think our techniques amount to the same idea. I was taught to use circles starting with just moving around  a tiny bit within the space of the actual metal piece you are working on, then like an ever increasing diameter spiral as you move out. Perhaps visualizing a cone shaped spring as your path would help. This keeps you in close proximity for a bit if you don't move too fast, and lets you do some movement that gradually decreases the field (which is the point) without having to move veeerrrry slowly away in a linear fashion which also works. I am a bit of a klutz and my hand is not completely linear so the critical part of not jerking or moving too fast or eratically in very close proximity to the heads etc. is better handled by me with the retracting in larger circles technique. However you do it the first part is the most critical, probably up to an inch or two away. I don't think it falls off in a linear fashion so as long as you don't rapidly change the field when within an inch or so you should do no harm. You might have to linger a bit longer almost, if not touching, the part if you have a normal home demagnetizer and you suspect a big issue with some part. Not such a big deal from just normal playing or even recording of tapes unless your machine circuitry is messed up and trying to put DC across the heads or you adjusted the guide with a magnetized screwdriver. If that is the case it needs to be fixed THEN thoroughly demagnetized.
Steve Williams

you don't want to know what equipment I listen to...

Offline oneobgyn

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Re: LAST Tape Preservative - First Try
« Reply #18 on: March 25, 2009, 07:54:58 AM »
Is there risk to any of my adjacent components as long as these are powered off?
There's ALWAYS another Steve Williams BUT there's only "oneobgyn"
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Offline ironbut

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Re: LAST Tape Preservative - First Try
« Reply #19 on: March 25, 2009, 10:24:06 AM »
I was about to respond to your question Steve as saying simply," I've never heard any warning about equipment, or had any problem from demagnetizing,.." and I was going to add the caveat " but you might survey the immediate area before using it to be sure that there are no tapes, or devices which have hard drives in them". But as I thought about what I was just about to type, I looked over at my Technics and realized that 4 inches on the right of my machine is the cabinet that holds about 100 of my tapes and 10 inches below it, is my Mac Pro! I guess I might think about rearranging some things!
That reminds me of the first time I took a patient (I'm an RN) to have an MRI done. The procedure at the time was to ask the patient 3 times whether they have any metal objects within their body and once in writing. I did this and while wheeling my patient through the long underground corridors to the MRI dept. (it's always isolated from the rest of the hospital) I went over the checklist in my head. I asked the patient one more time as I when I got the patient into the MRI room on a plastic gurney and when I got within about 10 feet of the machine, my metal clipboard, stethoscope, and every pocket I had jerked towards it! It took everything I had to keep them from flying away and not to show the panic I was feeling to the patient. As I walked out (I never shoulda been in there in the first place) I could see the techs laughing their asses off.
Now that's a strong magnetic field! Obviously, your RB Annis is nowhere near this strong and I haven't had any problems with my tapes or hard drive, but there's no reason to test fate.
steve koto
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Offline steveidosound

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Re: LAST Tape Preservative - First Try
« Reply #20 on: March 25, 2009, 11:10:49 AM »
Again, I defer to the opinions of others here and there is no accounting for what subtle effects might be noted in audiophile circles, but the answer would be no. I don't think you could hurt anything. The field decreases rapidly with distance from the probe end.
The "having the equipment off" part is so you don't accidentally induce a loud hum or pop into the electronics. The demagnetizer produces an AC field at 60Hz at the tip while it is on, but it makes an inductive spike pulse when it's power is turned off. Again, see the Jay McKnight article.
It is basically an AC coil hooked to the 120V power line and works on the same general principle as a bulk tape eraser or one of those rings that they used to use to degauss (demagnetize) the shadow mask of a color picture tube. The idea being if you put an object in a strong magnetic field that reverses polarity rapidly at 60Hz line frequency, then slowly reduce that field to zero, you remove whatever "permanent" magnetism has built up and leave the object at "zero" magnetic potential.
In effect that is exactly how the erase head on the recorder works as well. It puts the (much higher) bias frequency with no signal on the tape to erase whatever magnetic signal used to be there. 
I suppose a mechanical VU meter might be an issue if you get the demagnetizer probe too close, or tapes themselves.  Perhaps you could subtly physically distort the relationship of the elements within a small delicate tube with a very big demagnetizer, but I think you would have to try very hard to do that.
Just don't turn the power off or on near anything or get it close to your tapes or mechanical VU meters.
« Last Edit: March 25, 2009, 11:21:36 AM by steveidosound »
Steve Williams

you don't want to know what equipment I listen to...

Offline steveidosound

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Re: LAST Tape Preservative - First Try
« Reply #21 on: March 25, 2009, 11:16:49 AM »
I looked over at my Technics and realized that 4 inches on the right of my machine is the cabinet that holds about 100 of my tapes

I wonder how many people have stored their tapes right next to their bookshelf loudspeakers with big woofer magnets through the years and if anyone has noticed an effect from it.
Steve Williams

you don't want to know what equipment I listen to...

Offline oneobgyn

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Re: LAST Tape Preservative - First Try
« Reply #22 on: March 25, 2009, 11:39:01 AM »
Thanks for all of the great advice guys and sorry to have taken the thread off topic.
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Offline ironbut

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Re: LAST Tape Preservative - First Try
« Reply #23 on: March 25, 2009, 11:39:23 AM »
Yeah, like I said, I've never noticed any problem with those tapes and I store some of my favorites in the closest spot. I have heard rumors that laying tape against high efficiency speakers with huge permanent magnets have had problems.
In the "Tape Basics" part of the Beginners Guide, I tried to impress upon the reader how drasticly distance effects magnetic force. If you place a couple of pages of paper under a fridge magnet, it holds it up just fine. If you increase those pages, the magnet will no longer hold the pages to the fridge. If you investigate the reason by pulling the magnet off with different thickenesses of the same paper, you'll see that it isn't the wieght of the papers, it's the decrease on magnetic attraction.
steve koto
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Offline TomR

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Re: LAST Tape Preservative - First Try
« Reply #24 on: March 25, 2009, 10:31:08 PM »
And just how did my original thread get so hijacked?

Actually, the discussion on demagnetizing is a good one, and perhaps someone more technical than I am can extract the info and add it to a sticky on RTR basics.
Thomas Ream

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