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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 22nd Feb 2021, 10:28 am   #21
ajgriff
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Default Re: Head demagnetizer cassette

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Originally Posted by Plus4db View Post
There are times a head can become magnetized, e.g. if you test them for impedance with an ohm meter, but it is other wise very rare.
I know that conventional wisdom states that measuring resistance can magnetise heads but I wonder whether or not a quick check with a modern DMM really has much effect?

Alan
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Old 22nd Feb 2021, 11:02 am   #22
Plus4db
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Default Re: Head demagnetizer cassette

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Originally Posted by ajgriff View Post
I know that conventional wisdom states that measuring resistance can magnetise heads but I wonder whether or not a quick check with a modern DMM really has much effect?

Alan
I think it's the same since you are putting DC current through them, whether the measuring method be digital or analogue, though probably not a massive issue. It is any case probably a wise precaution.

Interestingly, I have noticed that sometimes on my deck when I set it to record I get a rumbling noise that sounds like the heads are magnetized. It disappears completely when I switch the individual track enable record switches out and in whilst in record. At first I thought they need deoxit but all of the switches have been gone through. It seems remarkably like this action is demagnetizing, which is contrary to received wisdom - Ferrograph particularly said this action would possibly magnetize the heads.

It probably is just dirty switches still, since I don't know how the heads would become magnetized so easily, but it doesn't sound like the higher crackle you normally get with that and out and in once only always removes it.
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Old 23rd Feb 2021, 12:06 am   #23
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Default Re: Head demagnetizer cassette

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There was a service bulletin on the Revox B710 discouraging routine use of a demagnetiser on the grounds that it led to premature demagnetisation of the capstan motor rotors. In practice, these machines seldom mag up outside of fault conditions.
Of course demag tools come in various shapes, sizes and strengths of field. A slightly magnetised cassette head would hardly need the power of an Annis Han-D-Mag. Hopefully technicians used their common sense.
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Old 23rd Feb 2021, 11:42 am   #24
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Default Re: Head demagnetizer cassette

I have a handheld TDK demag. It takes a couple of small batteries. You switch on and it takes a few secs to charge the caps, whereupon the green light turns on and you can use it. It discharges after a second or two, and you have to wait for it to recharge. I wouldn't stake my life on it making an audible difference.... I might try recording a 15K tone before and after using it. My partner's Yamaha deck has never been demagged (or cleaned before she met me!).
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Old 23rd Feb 2021, 12:57 pm   #25
TIMTAPE
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Default Re: Head demagnetizer cassette

Is this the one? I've had this one for decades, bought from a pawn shop. Using it so often for small heads and guides as in cassette decks I got sick of replacing the small button cells so I made a rough mod to run from two AA batteries instead. I never regretted that mod!

It's pretty battered these days. The protective plastic piece on the tip failed long ago so I replaced it with heatshrink.

I tested it recently and felt the decay may now be too fast. I must check the caps and replace if needed. Very handy tool.
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Old 24th Feb 2021, 10:21 am   #26
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Default Re: Head demagnetizer cassette

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I've had this one for decades. ..... I got sick of replacing the small button cells so I made a rough mod to run from two AA batteries instead. I never regretted that mod!

He He...I have done the same mod to it...Excellent tool!
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Old 24th Feb 2021, 11:38 am   #27
knobtwiddler
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Default Re: Head demagnetizer cassette

This put a smile on my face -) It is indeed, Tim. Purchased mine in Lasky's (anyone remember them?) some time around 1984/5 if I recall correctly.

Maybe I should try the same mod -)

To think that there was a chain such as Lasky's. I can picture the line of turntables as you entered the top floor (2 floors of audio - packed to the gills). It went on for several metres. Starting with the Duals and NADs, and increasing in price as you went along. I once saw a Krell power amp in there, underneath a shelf in a dark corner... Maybe it was a bit rich even for the mid 80s.
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Old 24th Feb 2021, 11:50 am   #28
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Default Re: Head demagnetizer cassette

I generally always clean my cassette drive system and heads by hand. But I still have a Metrosound cassette cleaner that, pretty much alone in the world of cassette cleaning 'machines', did actually work. It has felt pads at each end that you charge with cleaner and when you switch the machine to 'play' they 'scrub' the pinch roller and capstan very effectively, soaking up the detritus. Similarly, a felt pad scrubbed the heads. It was darned nearly as effective as doing it by hand and was great for quick use on difficult to access mechanisms.

I also use a mains powered 'fat pencil' demagnetiser.
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Old 24th Feb 2021, 1:30 pm   #29
Plus4db
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Default Re: Head demagnetizer cassette

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Originally Posted by TIMTAPE View Post
Is this the one? I've had this one for decades, bought from a pawn shop. Using it so often for small heads and guides as in cassette decks I got sick of replacing the small button cells so I made a rough mod to run from two AA batteries instead. I never regretted that mod!

It's pretty battered these days. The protective plastic piece on the tip failed long ago so I replaced it with heatshrink.

I tested it recently and felt the decay may now be too fast. I must check the caps and replace if needed. Very handy tool.
That's the one I had and a cassette one that you inserted. I found both very weak since they are DC powered. You can tell if a demagnetizer works by the strength of the buzz near the poles, or any metal. There is no need for those expensive Hand-De Mag ones, the generic curved AC ones all over ebay are fine. There is usually little danger in using them, just that they can destroy VU meters. I've accidentally switched one off near the heads before, without any lasting damage - I wouldn't advise it, of course, just that it's not as dire as they always say
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Old 24th Feb 2021, 2:09 pm   #30
stevehertz
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Default Re: Head demagnetizer cassette

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Originally Posted by stevehertz View Post
I generally always clean my cassette drive system and heads by hand. But I still have a Metrosound cassette cleaner that, pretty much alone in the world of cassette cleaning 'machines', did actually work. It has felt pads at each end that you charge with cleaner and when you switch the machine to 'play' they 'scrub' the pinch roller and capstan very effectively, soaking up the detritus. Similarly, a felt pad scrubbed the heads. It was darned nearly as effective as doing it by hand and was great for quick use on difficult to access mechanisms.

I also use a mains powered 'fat pencil' demagnetiser.
After reading an earlier post, I realise that the unit I mention (above) is in fact an Allsop 3 cassette cleaner and not as I said. Apologies for any inconvenience.
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Old 24th Feb 2021, 2:24 pm   #31
knobtwiddler
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Default Re: Head demagnetizer cassette



I think Allsop had a patent, although there were a few imitators. Personally, I regard it to be better than buds, as it scrubs capstans and tyres evenly.

I shall attempt a -10 / 15K recording on my partner's Yamaha pre and post treatment with the TDK. Finally, I shall know if it does anything!

(I would do it on one of my decks, but none of them work!)
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