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Demagnetizing Tape Heads

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Anonymous
May 8, 2005 3:49:57 AM

Archived from groups: rec.audio.tech (More info?)

I have a Sony double cassette tape deck and also an old Roberts
770-X reel-to-reel tape recorder. How often should I degauss the
play/record heads??? (I assume that *no* degauss is necessary for
the erase head).

Can the information on my tapes be damaged by a play head that
has *not* be deguassed??? If so, is the loss significant for
audio cassettes???

Where can I get a *lot* of information on the subject of degaussing
tape heads???

Thanx in advance!!!

--
+----------------------------------------------------------------+
| Charles and Francis Richmond It is moral cowardice to leave |
| undone what one perceives right |
| richmond at plano dot net to do. -- Confucius |
+----------------------------------------------------------------+
Anonymous
May 8, 2005 1:04:03 PM

Archived from groups: rec.audio.tech (More info?)

Charles Richmond wrote:

> I have a Sony double cassette tape deck and also an old Roberts
> 770-X reel-to-reel tape recorder. How often should I degauss the
> play/record heads???

At least prior to putting a calibration tape on them. In theory the
earth magnetic field (about half a Gauss) is enough to magnetize them,
but the risk from magnetized tools and nearby magnets is more like one
to loose sleep over.

> (I assume that *no* degauss is necessary for
> the erase head).

If a suitable degausser is used as the manual for it suggests the erase
head will be degaussed as will nearby ferromagnetic materials on the
tape head bridge.

> Can the information on my tapes be damaged by a play head that
> has *not* be deguassed??? If so, is the loss significant for
> audio cassettes???

YES! and YES! - it takes one pass only on a modestly magnetized
transport to loose the treble clarity, with more passes or stronger
magnetization a near complete erasure can be obtained and the tape
background noise (eletrictical) will increase with each pass.

> Where can I get a *lot* of information on the subject of
> degaussing tape heads???

http://lib1.store.vip.sc5.yahoo.com/usrecordingmedia-st...
is the product to get, assuming that it is complete with manual -
according to the webshop it is, and it may still be manufactured, the RB
Annis Handimag has been in my toolkit since 1976. Remember to demag
relevant tools too, and beware of screwdrivers with strongly magnetic
tip. Leave it in the kitchen or some other room and take whatever needs
demagging to it.

BTW. modern televisions run a CRT demag cycle via a coil around the CRT
whenever you turn them on, you should not leave sensitive magnetic media
- analog recordings constitute such - on top of them or within some 4
feet, immediately in front of or behind is possibly worse than on top of
or below.

I couldn't find anything about this in the newsgroup faq's index. The
mentioning of a web shop does not constitute endorsement, it was the
first place I found an image of the suggested implement. Mine is a 220
volt version, if they still make'm, they probably also still make those.

Mentioning the RB Annis Han-d-Mag does constite a recommendation of the
product. Do read the manual, it is the movement of the implement that
causes the demag, do not just place it near something and turn it on and
then off, doing that will leave said something strongly magnetized.

It is possible for those who really know what they are doing to DIY, but
all things considered, including that a suitable product is available
retail, I strongly discourage it for safety reasons. <small print
language>There are risks such as fire, electrocution and such that may
have a negative impact on your longevity expectation and thus reduce the
actual perceived benefits of your pension savings for you
yourself.</small print language>

> Thanx in advance!!!


Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************
Anonymous
May 8, 2005 3:08:28 PM

Archived from groups: rec.audio.tech (More info?)

On Sat, 07 May 2005 23:49:57 -0700, Charles Richmond
<richmond@plano.net> wrote:

>I have a Sony double cassette tape deck and also an old Roberts
>770-X reel-to-reel tape recorder. How often should I degauss the
>play/record heads??? (I assume that *no* degauss is necessary for
>the erase head).

Why do you assume that? You degauss the entire signal path.

>
>Can the information on my tapes be damaged by a play head that
>has *not* be deguassed??? If so, is the loss significant for
>audio cassettes???

Yes. Yes.

>Where can I get a *lot* of information on the subject of degaussing
>tape heads???

Follow the instructions that come with your de-gausser. If you are
cack-handed you can do more harm than good. The basic rule is DO IT
SLOWLY. Switch on the degausser well away from the tape machine.
Bring it in slowly. Sweep it over the heads and tape path slowly
and smoothly. Withdraw it slowly and, when it is well away, turn it
off. Obviously, keep all magnetic media well away from the degausser
at all times. That's about it.

When you Google for "Tape head degauss" you will find a lot of
information on bulk-erasing tape. Same idea, but a different
application. It rubs home the point about not waving the degausser
around in the vicinity of tapes, computer disks etc. though.
Related resources
Anonymous
May 8, 2005 3:55:18 PM

Archived from groups: rec.audio.tech (More info?)

In <427DB696.39DF58D2@plano.net>, on 05/07/05
at 11:49 PM, Charles Richmond <richmond@plano.net> said:

>I have a Sony double cassette tape deck and also an old Roberts 770-X
>reel-to-reel tape recorder. How often should I degauss the play/record
>heads??? (I assume that *no* degauss is necessary for the erase head).

Degauss every metal item that touches the tape, including the erase
head.

How often depends on your situation. I would suggest that you degauss
every 50 operating hours or prior to every important recording session,
whichever comes first.

I once owned a machine that was a big pain in the neck because there
was a small switching transient that tended to magnetize the heads.
After switching between play and record a few times, I'd have to stop
and degauss because there would be a very apparent increase in the
playback noise level. During an evening of recording I'd demagnetize
half a dozen times or more.

>Can the information on my tapes be damaged by a play head that has
>*not* be deguassed??? If so, is the loss significant for audio
>cassettes???

>Where can I get a *lot* of information on the subject of degaussing
>tape heads???

Others gave some references that I haven't checked.

Actually, one does not "demagnetize" anything. An atom either has a
magnetic "moment" or it doesn't. Single atoms don't exist in the wild,
the materials that we can see and touch are formed by clusters of
atoms. Each of these microscopic crystals forms a tiny magnetic
"domain" that will point (in the "north" or "south" magnetic sense) in
a direction. If most of the domains align and point in the same
direction, we will observe the bulk effect of a "magnetized" body.
These are the familiar magnets that we played with as a child and are
incorporated in all sorts of gadgets. The strength of the bulk effect
depends on the material involved and how thoroughly the domains are
aligned.

If the orientation of the domains is random, there is no net external
magnetic field and we conclude that the body is not magnetized.

When we degauss or demagnetize a body we bring a very strong (strong
enough to force all of the domains to align to the same direction)
external magnetic field near the body. We use an alternating magnetic
field that will alternately force all the domains to be north or south.
Effectively we are saturating (magnetizing as much as we can) the
material in one direction or the other. After we have established
saturation, we slowly withdraw the degausser. During this slow
withdrawal we loose contact with the tiny domains one by one and they
will retain their last orientation while the domains still controlled
by the alternating field will continue to follow. After the degausser
is completely withdrawn, the domains will be more or less randomly
oriented and the bulk material will be "demagnetized".

-----------------------------------------------------------
spam: uce@ftc.gov
wordgame:123(abc):<14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15
13> (Barry Mann)
[sorry about the puzzle, spammers are ruining my mailbox]
-----------------------------------------------------------
Anonymous
May 11, 2005 12:19:06 AM

Archived from groups: rec.audio.tech (More info?)

Barry Mann wrote:
>
> [snip...] [snip...] [snip...]
>
> When we degauss or demagnetize a body we bring a very strong (strong
> enough to force all of the domains to align to the same direction)
> external magnetic field near the body. We use an alternating magnetic
> field that will alternately force all the domains to be north or south.
> Effectively we are saturating (magnetizing as much as we can) the
> material in one direction or the other. After we have established
> saturation, we slowly withdraw the degausser. During this slow
> withdrawal we loose contact with the tiny domains one by one and they
> will retain their last orientation while the domains still controlled
> by the alternating field will continue to follow. After the degausser
> is completely withdrawn, the domains will be more or less randomly
> oriented and the bulk material will be "demagnetized".
>
Just one more stupid question from me...and a pointless one too, I guess.

Why is there *no* object measurement attached to tape machines...
like some sort of digital meter that reads out the magnetic field
density around the tape heads???

Sure would make me feel more comfortable...

--
+----------------------------------------------------------------+
| Charles and Francis Richmond It is moral cowardice to leave |
| undone what one perceives right |
| richmond at plano dot net to do. -- Confucius |
+----------------------------------------------------------------+
Anonymous
May 11, 2005 3:15:49 AM

Archived from groups: rec.audio.tech (More info?)

> some sort of digital meter that reads out the magnetic field
> density around the tape heads???

You really don't want to ask what it would cost.
Anonymous
May 11, 2005 1:29:49 PM

Archived from groups: rec.audio.tech (More info?)

Joe Kesselman wrote:
>> some sort of digital meter that reads out the magnetic field
>> density around the tape heads???
>
> You really don't want to ask what it would cost.

I have an analog (Gauss?) meter. Barely ever saw it deflect on a tape head,
but ocassionally guides and capstans are way more magnetized than you would
think, and a regular head demagnetizer is useless on a capstan.

Mark Z.
May 15, 2005 6:54:55 PM

Archived from groups: rec.audio.tech (More info?)

"Laurence Payne" <lp@laurenceNOSPAMpayne.freeserve.co.uk> wrote in
message news:imor719i5av5toelf2q6n17vqvcs9v5ksb@4ax.com...
> On Sat, 07 May 2005 23:49:57 -0700, Charles Richmond
> <richmond@plano.net> wrote:
>
>>I have a Sony double cassette tape deck and also an old Roberts
>>770-X reel-to-reel tape recorder. How often should I degauss the
>>play/record heads??? (I assume that *no* degauss is necessary for
>>the erase head).
>
> Why do you assume that? You degauss the entire signal path.

The erase head is not actually in the signal path. Of course, if it
were magnetized it would wreck the tape (as you are suggesting.)
Anyway, I think the poster is assuming that the erase head (when used)
is subject to a a full, saturating B-H curve swing of erase current at
50 kHz, or whatever (with a exponential switch off!) However, if the
player only ever plays tapes then the erase head could get magnetised,
so degauss it (I do!)
Cheers,
Roger

(snip)
Anonymous
May 23, 2005 12:33:24 AM

Archived from groups: rec.audio.tech (More info?)

On Sun, 15 May 2005 14:54:55 -0400, "Engineer"
<fakeaddress@nowhere.net> wrote:

>>>I have a Sony double cassette tape deck and also an old Roberts
>>>770-X reel-to-reel tape recorder. How often should I degauss the
>>>play/record heads??? (I assume that *no* degauss is necessary for
>>>the erase head).
>>
>> Why do you assume that? You degauss the entire signal path.
>
>The erase head is not actually in the signal path. Of course, if it
>were magnetized it would wreck the tape (as you are suggesting.)
>Anyway, I think the poster is assuming that the erase head (when used)
>is subject to a a full, saturating B-H curve swing of erase current at
>50 kHz, or whatever (with a exponential switch off!) However, if the
>player only ever plays tapes then the erase head could get magnetised,
>so degauss it (I do!)
>Cheers,


Wasn't "Signal path" a misprint for "Tape path"?
Anonymous
May 27, 2005 3:33:17 AM

Archived from groups: rec.audio.tech (More info?)

Joe Kesselman wrote:

>> some sort of digital meter that reads out the magnetic field
>> density around the tape heads???

> You really don't want to ask what it would cost.

The R.B. Annis Han-d-Mag comes with a gauss-meter included. Analog even.


Kind regards

Peter Larsen


--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************
July 23, 2009 7:53:11 PM

I have a GX 260D Reel To Reel Recorder/Player, since there hasn't been any
posts in 5 years just to update you they are still in use. My degauss tool is
a Aka i AH-8 unit it has been stored for many years but I came across some
tape on the internet now have over 500 plus 7" reel's plus some 5" and 4"
various numbers I am retired and now I am getting some regular enjoyment
out this equipment. Hope you are enjoying your's as well. J. Dickerson
!