head cleaning and degaussing
Graeme Lemin
decks? I have use cotton buds and isopropyl alcohol in the past. Is there a
particular technique which is better than others? Is there anything NOT to do,
so that the heads are not damaged?
What about demagnetising? How often should it be done? Can it be done at home
(I've heard some horror stories!)?
Thanks
Graeme
MICHAEL HAERTL
: It may seem a trivial question, but what's the best way to clean heads on
: tape decks? I have use cotton buds and isopropyl alcohol in the past. Is
: there a particular technique which is better than others? Is there anything
NOT to do,
: so that the heads are not damaged?
I've heard of small fine leather tips used instead of cotton buds.
Isopropyl alcohol should be ok. (imho).
I always try to clean in the direction of the running tape (for little
scratches).
Not just the heads but all parts meeting tape should be cleaned.
On recording sessions i clean at least daily.
: What about demagnetising? How often should it be done? Can it be done at
home
: (I've heard some horror stories!)?
When demagnetizing the deck should be switched off. Place the demagnetizer at
least 3 feet away from the deck and switch it on. Move it slowly to the parts
and move it with a distance of about .5" near the parts around. *AVOID*
touching anything with it. Other magnetic parts (like mech. VUs) should be
away otherwise they will be disturbed by the magnetic field of the
demagnetizer.
The distances or the whole procedure may vary, depending on the demagnetizer
itself (see instruction manual).
Important is NOT to TOUCH the parts of the machine, then you normally have to
replace them because they are permanently magnetized.
If anyone knows it better, I'd like to hear it, too, as most of my jobs are
life gigs.
Michael (also called KRACH, e-mail: hae...@eikon.e-technik.tu-muenchen.de).
rev...@umbsky.cc.umb.edu
Isopropyl alcohol works great for cleaning tape heads. Things
you should be aware of, however--
1) Don't scratch the heads (this should be pretty obvious)
2) Be kind to your capstan motor bearings. On some machines
(Studer A80 for example) capstan motor is not sheilded. Here's the
scenario--the capstan is sticking up in the air. You slop some
alcohol on it. If that q-tip is a little too saturated, the excess
drips down the side of the capstan, down into the motor, and
de-lubricates the bearings.
This ruins the motor.
Solution--hold a dry q -tip against the base of the capstan
while cleaning to catch the excess. Also--wring the sucker out
before you use it.
As far as degaussing:
1)TURN THE MACHINE OFF. The magnetic field created by a
degausser is alot stronger than the electronics are meant to deal
with. You could give them a potentially very damaging 'case of
indigestion( sort of like eating at taco bell....:-).
2) Start a few feet away (three-four). Turn the degausser on,
aand move in slowly to the machine. SStart at one side and work
towards the other. Run the deguasser SLOWLY up and down over each
part of the tape path. Go part by part, moving SLOWLY from each to each.
3) When you've covered all the parts, off. SLOWLY. Get a good
three-four feet away. Then switch the thing off. DO nOT TURN IT ON
OR OFFR WHILE IT IS NEXT TO THE MACHINE. This could put a permanent
magnetic charge on the heads that you will never remove.
4) Oh yeah, before you start degaussing, remove any tape or
other magnetic media out of the area.
All in all, it's really a very simple and routine procedure
thatcan be done tin the safgtey and privacy of your own home.
There's just a few things you need to be aware of, and you'll stay
clear of the horror stories.
Good luck
/sig
Peter Elsea
le...@rmit.edu.au writes:
>What about demagnetising? How often should it be done? Can it be done at
home
>(I've heard some horror stories!)?
Looks like good advice here so far.
About frequency of degaussing. It's better to do this when you think you
need to rather than on a regular basis. Ideal is to get a magnetometer.
(I have a very old one made by the Annis company of Indianappolis, I
don't know were to get one now.)
I found my need to degauss went WAY down after I bolted all my decks
down. Moving them is apparantly the best way to magnitize heads. Even
setting them loose on a table seems to encourage magging. Little bumps in
a strong magnetic field (the Earth's) I guess. That means demag them in
place, not on the test bench.
Symptoms of magnitization are loss of HF and mysterious pops appearing on
clean tape when the deck is parked.
Peter Elsea\
UCSC
Brandon Mathew
>
>About frequency of degaussing. It's better to do this when you think you
>need to rather than on a regular basis. Ideal is to get a magnetometer.
>(I have a very old one made by the Annis company of Indianappolis, I
>don't know were to get one now.)
I bought one from Annis about 6 month ago. Just call them up
(R.B. Annis Company in Indianapolis (USA) at +1.317.637.9282) and
they can sell you a magnetometer and a great degausser. But in
all honesty, I've never really used it (I've never seen it register
a value high enough to look bad before I degaussed). I simply
degauss before making a cassette copy. It does is a neet toy and
boy do I like toys...
--
Brandon Mathew - bra...@core.rose.hp.com
Mike Rivers
> It may seem a trivial question, but what's the best way to clean heads on tape
> decks? I have use cotton buds and isopropyl alcohol in the past.
Like most things in this busines, it depends. The isopropyl alcohol
and cotton swab will usually do the trick. If you're talking
multitrack recorder with fairly large heads that are out in the open,
there are easier ways. I use Texpads (isopropyl pre-soaked lintless
pads sealed in foil) for cleaning heads on my Ampex MM-1100, and used
to use them for my TASCAM 80-8 - just give 'em a swipe. For most
cassette recorders where the heads are stuck back in a hole, you
almost always need to use a swab on a stick. I prefer the long
medical swabs to the drug store Q-Tips.
> Is there anything NOT to do,
> so that the heads are not damaged?
One thing not to do is use drug store rubbing alcohol that's 70%
isopropyl, 30% water, and maybe a shot of lanolin thrown in. Go to
the druggist and ask for a bottle of pure (99% - it'll absorb a little
water as soon as the bottle is opened) isopropyl. You'll pay a couple
of bucks for it, but it'll last a lifetime. Commercial head cleaners
are OK, too, but cost more.
Cotton swabs are OK for stationary tape heads and guides, but you
shouldn't use them for rotary heads like on a VCR or DAT. If a thread
of cotton comes loose, it can snag in the rotating head assembly and
knock a head out of alignment if it gets caught wrong. For this kind
of head assembly, you should use the foam-tipped or chamois swabs.
Radio Shack sells them as "VCR Cleaning Swabs".
> What about demagnetising? How often should it be done? Can it be done at home
> (I've heard some horror stories!)?
Well, about the only horror story is that you can make it worse than
it was to begin with. Old time maintenance practice was to
demagnetize the heads every time you start a session, and if you did
that, you probably got enough practice so that eventually you did it
right. Nowadays, particularly with multitrack recorders, heads don't
get magnetized as much as they used to. Electronics are designed to
switch on the bias at the zero crossing of the cycle, and ramp it up
slowly, so there's not a near-instantaneous change in current through
the head. I have a magnetometer (came in a kit with a professional
demagnetizer) and check the heads for magnetism with that. When I see
some residual magnetism, I demagnetize. I guess I can put about 100
hours on it before I'll see the meter move.
--
I'm really Mike Rivers (mri...@d-and-d.com)
Dragon
>It may seem a trivial question, but what's the best way to clean heads on tape
>decks? I have use cotton buds and isopropyl alcohol in the past. Is there a
>particular technique which is better than others? Is there anything NOT to do,
>so that the heads are not damaged?
I also use Q-tips, but I've heard it recommended that you use foam swabs
to avoid letting the little cotton fibers get stuck in the capstan, etc.
In the video world we used chamois swabs, very expensive but they feel
good, and you can sew them together to make lizard coats. Don't use
stainless steel toothbrushes and all should be well...
>What about demagnetising? How often should it be done? Can it be done at home
>(I've heard some horror stories!)?
I think every 5 hours or so is what I heard, but if it's done properly
there should be no horror stories. The tape deck must be off, of course.
--
David Fiedler Internet:da...@infopro.com Phone:916/677-5870 FAX:916/677-5873
USMail:InfoPro Systems/Advanced Media Productions, PO Box 220, Rescue, CA 95672
Send mail with "info mixmasters" in the body to list...@infopro.com if you're
interested in improving your home audio recording and mixing skills...
Bob Olhsson
all honesty, I've never really used it (I've never seen it register
a value high enough to look bad before I degaussed). I simply
degauss before making a cassette copy. It does is a neet toy and
boy do I like toys...<<
You probably did not need to degauss at all!
The early Ampex professional recorders had a design "feature" of magnetizing
the heads if they lost power while in record. In what has to be a classic
case of turning a bug into a feature, Ampex built and sold a head
demagnetizer suggesting that frequent head demagnetization was a good idea
without mentioning HOW one's heads might have become magnetized in the first
place. Like sheep, the other recorder manufacturers have always dutifully
reccommended regular degaussing in their owners' manuals.
It all came back to haunt Ampex when their first 2" 16-track heads responded
to the Ampex demagnetizer by becoming magnetized. Ampex then held seminars
where they recommended the use of magnetometers and candidly admitted that
it is almost unheard of for heads to become magnetized other than from poor
demagnetizing technique!
Then equipped with our brand new magnetometers we discovered that Ampex and
other manufacturers occasionally shipped machines with capistans and tape
guides that were so magnetized that they couldn't be degaussed at all in the
field!
Bob Olhsson
James Addie
>In article <lemin.23...@rmit.edu.au> le...@rmit.edu.au writes:
>> It may seem a trivial question, but what's the best way to clean heads on tape
>> decks? I have use cotton buds and isopropyl alcohol in the past.
>Like most things in this busines, it depends. The isopropyl alcohol
>and cotton swab will usually do the trick.
-SNIP-
>> Is there anything NOT to do,
>> so that the heads are not damaged?
>One thing not to do is use drug store rubbing alcohol that's 70%
>isopropyl, 30% water, and maybe a shot of lanolin thrown in. Go to
>the druggist and ask for a bottle of pure (99% - it'll absorb a little
>water as soon as the bottle is opened) isopropyl. You'll pay a couple
>of bucks for it, but it'll last a lifetime. Commercial head cleaners
>are OK, too, but cost more.
The usual additive is glycerin (to make it rubbing alcohol). If you
don't want to spend the extra bucks and sign a controlled substance form
insome states, hardware stores sell "wood
alcohol" which is essentially the same stuff, and quite effective.
No additives to depsosit on heads, etc.
>> What about demagnetising? How often should it be done? Can it be done at home
>> (I've heard some horror stories!)?
>Well, about the only horror story is that you can make it worse than
>it was to begin with. Old time maintenance practice was to
>demagnetize the heads every time you start a session, and if you did
>that, you probably got enough practice so that eventually you did it
>right. Nowadays, particularly with multitrack recorders, heads don't
>get magnetized as much as they used to. Electronics are designed to
>switch on the bias at the zero crossing of the cycle, and ramp it up
>slowly, so there's not a near-instantaneous change in current through
>the head. I have a magnetometer (came in a kit with a professional
>demagnetizer) and check the heads for magnetism with that. When I see
>some residual magnetism, I demagnetize. I guess I can put about 100
>hours on it before I'll see the meter move.
I went around on this a decade or so ago. What I found out (from Mr.
Annis himself!) was the magetometer is calibrated in a large
crossection magnetic field - something several inches across. It is
impossible to insert any part of it into the field concentrated around
the gaps of tape heads, and is therefore not possible to read the
residual magnetism on this device. It was intened for use on guides,
motor shafts, etc. where the field crossectional area is large enough to
properly measure. Of course, the earths field is of sufficiently large
cross section to completely affect the magetometer and confuse things
thoroghly.
I went to the lengths to obtain a Bell Gaussmeter in an effort to measure
residual magetism on a tape recorder. The smallest probe then available
was less than 0.1" thick and 0.25" wide. I found I still could not get
reliable readings of the residual (deliberately magnetized) heads. The
readings I could get were very low - far below the coercivity of any tape.
Next I set up an experiment of heavily magnetizing a head and passing a
loop of tape over it with a 20-20kHz sweep recorded on it for about 10
seconds duration. The loop ran constantly for 8 hours. I was able to
measure a slight loss in high frequency response, but I could attribute
that just as easily to wear as erasure.
I then brought a magnet near to the tape as it passed over the gaussmeter
probe acting as a temporary tape guide. When the flux reached a level
near tape coercivity - in the 100 gauss range, if I recall - erasure
began to occur. I could never magentize any tape recorder parts to a
level this high, even with a strong permanent magnet. If this were the
case, I reasoned that tape playback would never magnetize any tape
machine parts.
I then wondered what would happen if a DC field were introduced in the
record process - as if the record head were magnetized. The exact field
strenght was hard to measure, but I recorded a 1KHz tone and as I did so
I broght the permanent magnet close to the record head. On a swept
spectrum analyzer, the even order harmonic distortion crept upward first,
then the noise floor elevated. The equivilent field was again quite high
- but somewhat lower than what was required for erasure. I determined
that the only way residual magnetizm could be measured was to check the
even order harmonic distortion and noise floor. The noise check was easy
to do with any noise meter, but the harmonic check requires harmonic
analysis with a _swept_ spectrum analyzer with sufficiently narrow
filters. This test is very sensative, and is the definitive residual
magnetizm check. I also found that demagnetization technique was very
very important. It was quite easy to increase the magnetization and not
quite as easy to decrease it. I concluded that if the symptoms are not
present, don't demagnetize since the chances are good you will increase
the problem.
Lastly, I found that materials used in tape recorder heads and guides of
the last 25 years have a natural magnetic polarization that is very
nearly neutral. If a head is magnetized by the record or play circuitry
(that's really the _only_ way it can happen - moving tape will never do
it) if the machine is left off for a period of time, the magnetized parts
will revert to their normal state of polarization which is, if properly
designed, neutral. From this I concluded that if residual magnetism is
detected by observing symptoms, the cause should be found. Check for DC
on the heads, or a starting/stopping transient of a particular polarity,
or asymetry of the bias signal. Bias will, if low distortion and
symetrical, demagnetize the record and erase head. Sloppy bias switching
would be a cause to look at as well. The last cause, and I did find
this, but it's relatively rare, is parts that have a natural magnetic
polarization that's strong enough to generate the symptoms outlined
above. Simply replace the parts.
After having worked in a ficility with close to 60 tape recorders to
maintain, I feel confident in saying, " don't demagnetize unless you
detect symptoms of residual magnetization - don't do it routinely,
especially without a swept spectrum analyzer" and the magnetometer is
useless for, and not intended for measuring the residual fields on tape
heads.
Jim Addie
AddieTech Inc.
Consultants to the audio industry
--
Jim Addie "Snakes! Why did it have to be snakes?"
AddieTech, Inc. "Asps. Very dangerous. You go first..."
N9SSD
Bill Vermillion
I used a magnetometer and found that the incoming capstan, the
one attached to the 4th motor on our MR-70, was highly
magnetized. I could not degmag with the Handi-Mag.
So I removed the idler, and took it to a tape duplication house
that had units used to demag 2" video tape. That cured it.
We demagged only occasionaly - counter to the current trend of
demag often. We also found on the 1/4" like the ATRs it was
easier to pop the head stack and put them on the bulk
degmagnetizer we used for our 2" tapes. (we didn't have one
in the first instance - in our second studio - but had one in
our third and final incarnation).
--
Bill Vermillion - bi...@bilver.oau.org | bill.ve...@oau.org
Mike Rivers
> (R.B. Annis Company in Indianapolis (USA) at +1.317.637.9282) and
> they can sell you a magnetometer and a great degausser. But in
> all honesty, I've never really used it (I've never seen it register
> a value high enough to look bad before I degaussed).
Then you haven't needed to degauss. It works. Trust it.
If you want to experiment, try magnetizing a screwdriver just enough
so it causes the magnetometer to go off center. Then record a high
frequency tone on a piece of tape - 15 kHz or so - and see if you can
partially erase it with the screwdriver's magnetism. Send in three
copies of your lab report. Neatness counts.
h...@hsan.loc.gov
>The early Ampex professional recorders had a design "feature" of magnetizing
>the heads if they lost power while in record. In what has to be a classic
When did they eliminate this feature? I have two 351s (NOT
AG-351s). I recall something in the manual (I think) about not
pressing the record buttons for a few seconds after the transport
comes up to speed to avoid magnetizing the heads.
These opinions are my own, not those of the Library of
Congress.
Howard Sanner
h...@hsan.loc.gov
san...@mail.loc.gov
h...@hsan.loc.gov
>In Article <lemin.23...@rmit.edu.au>
>le...@rmit.edu.au (Graeme Lemin) writes:
> As far as degaussing:
>
> 1)TURN THE MACHINE OFF. The magnetic field created by a
> degausser is alot stronger than the electronics are meant to deal
> with. You could give them a potentially very damaging 'case of
> indigestion( sort of like eating at taco bell....:-).
>
> 2) Start a few feet away (three-four). Turn the degausser on,
> aand move in slowly to the machine. SStart at one side and work
> towards the other. Run the deguasser SLOWLY up and down over each
> part of the tape path. Go part by part, moving SLOWLY from each to each.
> 3) When you've covered all the parts, off. SLOWLY. Get a good
> three-four feet away. Then switch the thing off. DO nOT TURN IT ON
> OR OFFR WHILE IT IS NEXT TO THE MACHINE. This could put a permanent
> magnetic charge on the heads that you will never remove.
How slow is "slowly"? A minute on each part of the tape path?
Less? More?
I've wondered this for years. I've been using one minute for
each part because I've never seen a figure for what's really
needed.
Mike Rivers
> hardware stores sell "wood
> alcohol" which is essentially the same stuff, and quite effective.
> No additives to depsosit on heads, etc.
It's not essentially the same stuff - it's methyl alcohol. It might
be OK for cleaning (and I've heard specific warnings against using it,
too) but you have to read the label carefully. It's highly poisonous
and it often has something added to make you vomit it quickly if you
swallow it. Yuck!
I know how much it pains people around here to spend $4 on a
commercial product when they can get what someone says is the same
thing at the hardware store for $1, but is it worth taking the risk?
If you had to buy a bottle every week, it might be worth doing the
research, but I don't think I've bought a bottle of alcohol in 10
years. I'd say 30 cents a year is a pretty good investment in not
worrying about whether I've been cleaning my heads with the wrong
chemical for 10 years.
> I went around on this a decade or so ago. What I found out (from Mr.
> Annis himself!) was the magetometer is calibrated in a large
> crossection magnetic field - something several inches across. It is
> impossible to insert any part of it into the field concentrated around
> the gaps of tape heads, and is therefore not possible to read the
> residual magnetism on this device.
What's the 'wand' that they provide with it for, then? I used to
think my heads on my MM-1100 were magnetized all the time until I
discovred that it was responding to the meter magnets, which are close
enough to register. Now when I want to check the heads, I take them
off.
> Next I set up an experiment of heavily magnetizing a head and passing a
> loop of tape over it with a 20-20kHz sweep recorded on it for about 10
> seconds duration. The loop ran constantly for 8 hours. I was able to
> measure a slight loss in high frequency response, but I could attribute
> that just as easily to wear as erasure.
That's a good experiment. I kind of suspected that the effect of head
magnetism was somewhat overrated. They used to sell a "spot erase
wand", which was a permanent magnet on a handle, but as I recally, you
had to touch the magnet to the tape directly to do anything. That was
in the day when you couldn't hear much above 10 kHz on tape anyway, so
it could be that it would have caused some damage to recordings that
you couldn't reproduce.
> I then wondered what would happen if a DC field were introduced in the
> record process - as if the record head were magnetized.
I would suspect that there would be some audible effect there, as it
changes the bias point of the head.
> After having worked in a ficility with close to 60 tape recorders to
> maintain, I feel confident in saying, " don't demagnetize unless you
> detect symptoms of residual magnetization - don't do it routinely,
> especially without a swept spectrum analyzer" and the magnetometer is
> useless for, and not intended for measuring the residual fields on tape
> heads.
Thanks for sharing your experiments with us.
Hans-Christian Becker
mri...@d-and-d.com (Mike Rivers) writes:
> > Next I set up an experiment of heavily magnetizing a head and passing a
> > loop of tape over it with a 20-20kHz sweep recorded on it for about 10
> > seconds duration. The loop ran constantly for 8 hours. I was able to
> > measure a slight loss in high frequency response, but I could attribute
> > that just as easily to wear as erasure.
>
> That's a good experiment. I kind of suspected that the effect of head
> magnetism was somewhat overrated. They used to sell a "spot erase
Well folks, that's what I used to believe as well. (BTW, I'm doing
Physical
Chemistry for a living, so don't believe *everything* I say ;-)
While modifying a ReVox A77 HS (*very* maltreated; the chassis was
broken!),
I desoldered the leads to one channel on the playback head, and later
resoldered them. After that, playing a tape (even blank ones) would
give
*very* strong noise on that channel, while the other was as quiet as
ever.
The noise also included a rumbling part, making the tape sound like a
bad
vinyl record. Degaussing helped. About an hour later I hooked up a
'scope
to the head, and *in the very moment* I connected the *ground* terminal
of the 'scope to the head (thereby possibly creating a ground loop to
the other 'scope probe, dunno) *the noise came back*. Degaussing fixed
the problem. Comments anyone???
Best Regards,
/hcb
---
Hans-Christian Becker -- h...@phc.chalmers.se --
Dept. of Physical Chemistry
Chalmers University of Technology
---
If I only knew how to get this #$! signature feature working!
James Addie
>In article <3dpf4t$i...@spruce.cic.net> jsa...@colum.edu writes:
>> hardware stores sell "wood
>> alcohol" which is essentially the same stuff, and quite effective.
>> No additives to depsosit on heads, etc.
>It's not essentially the same stuff - it's methyl alcohol. It might
>be OK for cleaning (and I've heard specific warnings against using it,
>too) but you have to read the label carefully. It's highly poisonous
>and it often has something added to make you vomit it quickly if you
>swallow it. Yuck!
Just to clarify (perhaps a resident netchemist could help out?) what we
used was completely denatured alcohol, called SDA 3A with a bit of
isopropyl added to make it undrinkable which it would otherwise be.
At one time we had determined that wood alcohol was quite similar, but
since we were buying this stuff from a commercial chemical supply house,
we never did use it. 20 years ago I bought a phamasutical (sp?) grade
wood alcohol (had to sign for it) for the same purpose.
Truely bad to drink, even to induce vomiting - use Ipecak.
>I know how much it pains people around here to spend $4 on a
>commercial product when they can get what someone says is the same
>thing at the hardware store for $1, but is it worth taking the risk?
>If you had to buy a bottle every week, it might be worth doing the
>research, but I don't think I've bought a bottle of alcohol in 10
>years. I'd say 30 cents a year is a pretty good investment in not
>worrying about whether I've been cleaning my heads with the wrong
>chemical for 10 years.
We used about a gallon per year - lots of heads, lots of use, lots of
cleaning. It was a matter of cost and convenience.
>> I went around on this a decade or so ago. What I found out (from Mr.
>> Annis himself!) was the magetometer is calibrated in a large
>> crossection magnetic field - something several inches across. It is
>> impossible to insert any part of it into the field concentrated around
>> the gaps of tape heads, and is therefore not possible to read the
>> residual magnetism on this device.
>What's the 'wand' that they provide with it for, then? I used to
>think my heads on my MM-1100 were magnetized all the time until I
>discovred that it was responding to the meter magnets, which are close
>enough to register. Now when I want to check the heads, I take them
>off.
The (magic) wand is for getting some reading on smaller cross sectional
fields, but not as tiny as a head gap. Also, the meter is not calibrated
with the wand in use.
>> I then wondered what would happen if a DC field were introduced in the
>> record process - as if the record head were magnetized.
>I would suspect that there would be some audible effect there, as it
>changes the bias point of the head.
It changes the symetry of the bias. One half cycle is overbiased, the
other is under - hence, the high even order distortion, which is, of
couse, _much_ less audible than odd order. The most noticable was the
increase in noise, and the gravely character of the noise.
>Thanks for sharing your experiments with us.
Always happy to share knowlege -now if I could only find a way to get
_paid_ for it....
Ah, but it's more fun for free anyway.
Regards to all,
Jim Addie
AddieTech, Inc.
Graeme Lemin
do enjoy reading everything that's discussed here.
You've convinced me that my head cleaning technique is ok, and maybe I
won't worry about the degaussing...... :-)
Later!
Graeme