Demagnetizing tape heads

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You need AC to demagnetize anything....
The DC thingies for casssettes I have never used....they must contain some inverter to generate an AC field, but I don't think they have enough energy to demag a proper head.

You can make one.... LOTs of thin wire turns of a soft iron core,- something liike a 5 inch nail or similar.... enough windings to be fed by any 9-12 V AC adapter without blowing fuses, - should do the trick.....

You operate it by moving it as close to the heads as possible, without scratching the head, - then remove it slowly....repeat a couple of times...

There might be DIY descriptions out there, and several makes were sold some years ago..... do some googling.....
 
Han-D-Mag

http://blevinsaudioexchange.com/handmag.html

is supposed to be a good one but at that price, I will not even think of buying one.

You can make one.... LOTs of thin wire turns of a soft iron core,- something liike a 5 inch nail or similar.... enough windings to be fed by any 9-12 V AC adapter without blowing fuses, - should do the trick.....

Isn't a 5 inch nail a bit oversized for this task?

What AWG do I take to build one?


Surprisingly, I haven't found any DIY demagnetizer. The only resources I can find are "how to demagnetize tape heads". There's no guide on what you should use or anything.
 
Had a look at the link.... this is exactly what I had in mind....price isn't really bad either, but for one-time or sporadic use, maybe a little bit high...

A suitable coil could be some hundred turns of AWG 38-40-42, or in that range... yo need a coil to produce a strong AC field without drawing too much current from the transfo.........some 40-50 mA should be enough...which makes coil impedance of 2-300 ohms at 50 ( or 60) Hz.

Come to think of it...if you can find an old 12V relay, possibly of the larger kinds, with round or oblong coil square section, - they used to be about 2 " long,... should be an OK coil for the purpose....then make a core ( or wand if you like ) out of some soft iron, -- you see the shape in the link...put some shrink tube over the tip to protect the heads.... should do the job....
The core should be soft grade iron, -- not any stainless or high grade alloy....

REMEMBER -- DO NOT DEGAUSS WITH POWER ON THE RECORDER!!

EDIT : After some thinking-- you probably need a lot more field strength than the DIYthing I just described.....
 
The cassette demagnetiser is handy for things like car cassette players, where you can’t easily get at the heads and tape path. They work pretty well – the original was designed by TDK, who are one of the major tape manufacturers. There was also a very good cassette version designed by Discwasher, which had an exceptionally strong permanent magnet in it, and used some trickery to decay the magnetic field – I think they used some kind of magnetic shield. The hi-fi magazines tested it back in the early 1980’s, using equipment to measure the magnetic field left after use, and it actually did a very good job. However, the cassette versions only demagnetize the tape head, not other metal sections in the tape path, so it is best to use one of the AC versions. Quoting from my TEAC Information Supplement, Stereo Cassette Tape Deck:

1. Turn the deck power off.
2. Turn on the demagnetizer and bring the tip of it close to the heads. Move the tip up and down across all the heads and other parts in the tape path.
3. Slowly withdraw the demagnetizer about 12 inches (30 cm) away from the head area.
4. Turn off the demagnetizer.

Be sure to keep all recorded tapes away from the demagnetizer during the demagnetizing of the heads. (End of quote.)
 
cheap diy degmatizer

HI EVERYONE!
I have same problem with my NAKAMICHI DRAGON. I trayed many types demag.,and finaly I made my own diy .
I used old RUSSIAN soldering gun(mains 220 v)I disconnected
tip and instead of it , put coil of PVC insulated 2,5sqr mm,3 layer of 10 windings. That all.GOOD LUCK .
 
Hello Everyone, I am new here at DIYaudio, sure glad to have found you guys :cool:

My buddy Steeve just bought an Han-D-Mag from eBay for around $80. He brought it over to show me, so i thought, why don't i try it first on my Roland Re-301 Space Echo!
Well... I did, and now i have 0 echo after doing the demag and installing a brand new loop in it (the right one the right way).

What could be the cause of this? I am scared to have fried my heads :eek: paid 1k for this unit, and it's a whole part of my guitar sound!!! I have been using it for 3 years steady, til yesterday!
I am very worried and confused :confused:

Any Idea?
 
Has it been demagnetized correctly? (ie. unit turned off, demagnetizing with circular movements, slowly walking away from it, and disconnecting it after being about 10ft from it.)

If it wasn't, maybe the head is so magnetized it can't move now.

I read some talk about demagnetizers recently, and no one has heard of problems after demagnetizing heads with the Han-D-Mag.

Is the transport still turning properly?

I found a service manual, the heads are always connected to the circuit, the electronics could have fried...

The problem could be on the recording side, I don't see how the demag could screw the four playback heads and circuits at the same time, unless the design is very sensitive.

Anyways, it could just be something else maybe? (Connector, etc.)
 
Hello Antoine, Thanks for your reply :)
Yes, the unit is performing as it should (as usual)
I think it's like you have mentionned, the heads might be magnestized big time (by the han-d-mag! :()

Is there a way i can undo this ?

Maybe if i try another new tape loop in it? :confused:

My tape loops are made of high end data carrier materials, it is above mastering tape (900) quality.

I'll try a new tape in it and i'll keep you posted on developments :Popworm:
J.
 
You need to demagnetize them again, that's what the Han-D-Mag is for ;-)

The trick is to do slow circular movements, and walking slowly backwards until the unit is far enough. The Han-D-Mag is so powerful that it can cause quite a bit of magnetization if it's not properly used.

Also, note that during the procedure, try not to do any abrupt movements, it could magnetize things (Sadly, mains only work at 60Hz, this is causing this problem).

I don't know if another loop would help, but if it has been magnetized with DC, it would be a good idea to put it on a bulk demagnetizer. It will return it to a brand-new state. (Any tape being demagnetized on a bulk demagnetizer rather than just being erased by a deck's erase head will perform like-new until physical wear starts to make it impossible to use.)
 
Wow! Thanks DragonMaster, I feel better, i'll try it again and see what happens.
When i demaged, i moved the tip on all surfaces including the tape tank and i finnished with the heads coming in near the head and wobbeling the tip from left to right while pulling away about 1 foot, then i would come back to the next head and do same! Thing is the heads are all next to each other.. so i guess would be best to just do it once pull away and unplug the han-d-mag.

some times i could feel the Han-d-mag vibrate more on some of the passes! donno why though! :xeye:

(My unit was turned off when i did this.)
 
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