Tape head demagnetization

My car (built-in) tape player seems to be getting strange in its
volume. Associated radio is fine, tape volume is down. I thought
that I should demag the tale head. But, the opening is only barely
big enough to insert a tape, and my 120V 60Hz demagger has a 1/2" long
tip at 1/3" diameter, affixed on the end of a tube that is at least 1"
diameter so there is no way to get the demagger tip anywhere near the
tape head. I could maybe tape a large nail to the end of the existing
tip, and reach the vicinity of the head, but I don't think that will
so anything. I don't know what the magnetic structure is under/inside
the head, but assume it is shaped to deliberately have flux going
outside the head. It's not worth it to make a coil small enough to
fit into the opening. I understand there are demagnetizing tapes
available, but I am cheap and don't want to spring for the $$ unless I
am reasonably (66+%) sure it will work.

Thoughts, ideas, polite suggestions.

 

A magnetized head will cause loss of high frequencies long before there's a
drop in volume.

The deck probably has some other problem.

 

Thanks Bill and Gareth,

OK - that's two votes against demagnetizing, plus I was skeptical
myself. So, now I have to decide whether to move my tapes to CD's, or
tear into a 10 year old car radio/tape player /cd player. I think it
will be easier to move a few tapes to CDs than tear up the car radio.

 

First check the tape on a known good tape player.
Or use a original prerecorded tape.

Tapes recorded on a machine with bad aligned heads will play good on
that machine, but not on others.

Clean the head. Clean the tape guides.
Demag if you can.
Adjust the head in height for maximum output.
Adjust the head azimuth to maximize high frequency.
And repeat the last two.

A magnetized head will destroy all your tapes (bad signal to noise
ratio). And can not be undone.

 

loss of volume? doesn't that mean gunk building up that keeps the tape
too far away form the head? Or, mean some component is lost? like a
coupling cap that has seen better days? Or, something as simple as
one of the wiring connections in the cabling has gone high resistance.

Sadly, my favorite tapes were made during the era of poor mylar
coating and have all turned 'squeaky' and unplayable! I wish I could
have transferred them before they died, but hindsight.

 

I'd give up on head demagnetizing. It's not likely the problem.
And you're more likely to magnetize it with the demagnetizer
unless you disassemble the thing so you can get at it.

Tape players don't last in cars.
I've only had two CD players and they were worse.
The heat, outgassing of plastics, dirt, etc. get all over the optical
and mechanical stuff.
Luckily, my last player has a USB slot and a Flash Card slot.
It won't play a CD any more, but the SD card works fine.

As for old tapes...
If you have rare music, you're pretty much screwed.
If you have popular stuff, there's an option.
Go to the library, check out a CD. Copy it back to the tape.
If you bought the tape, you own the license to play it.
The nitpickers will argue about it, but I think you're
on solid moral and legal ground to refresh the media.

 

Sounds like very dirty heads , or head alignment has gone out of whack. This
happens when one or both head mounting screws loosen. Happens occasionally.

Mark Z.

 

On Sat, 24 Nov 2012 16:35:30 -0800 (PST), Robert Macy

A trick I found for this squeaky problem to do a one time transfer was
to play them as cold as possible, unfortunately just freezing the tapes
doesnt last long enough - always thaught a head heatsink to a
deepfrozen al or cu block might do the trick but I never tried it!! I
just caught mine early enough! Mine were BASF

 

As others have said, this does not appear to be a magnetised head but it
could be that particles from your tapes has collected in the gap(s) on
the the tape head(s). The gap(s) need to be magnetically open so that the
passing tape completes the magnetic circuit and it is a very small gap on
a playback head (of the order of 0.0001 inch).

BTW, if you are using a head demagnetiser never switch it on or off
anywhere near the heads. Move a few feet away before switching off. One
spike and you will have magnetised them!

Many years ago I worked in the dev lab of Marriott Magnetics one of the
original makers of tape heads in the UK. Long gone.



Charlie.



--
M0WYM
www.radiowymsey.org

Sales @ radiowymsey
http://stores.ebay.co.uk/Sales-At-Radio-Wymsey/

 

I'd clean the head and capstan first, then worry about degaussing things.

 

Once upon a time i had a battery powered cassette sized tape head
demagnetizer. Sounds like just the trick for your situation, to determine
if it is head magnetization (perhaps unlikely) or some other problem.

?-)

 

Lucky you are, over 200 to transfer have i.

?-)

 

Depending on your tastes, some might be available now in CD or MP3 format.
You may have to buy a lot more than what you have to get all you want. I
have a lot of old music of the 1950s to 1970s range and an interesting bit
outside that range. Not all digital yet. You know how to find me.

?-)

 

(+1) on the dirty heads. I had forgotten.

?-)

 

Wow! Great tidbit!

 

Just to offer a different perspective, I onced repaired a Fujitsu Ten
auto-reverse car cassette player with the same symptom as yours. The
problem turned out to be a small dirty multipole switch. I'm a bit
hazy on the details, but ISTR that there were two head circuits, and a
different circuit was selected in forward and reverse mode.

As for demagnetising the head, I have a cassette tape with a built-in
battery powered demagnetiser that automatically activates when you
press the play button while the player is unpowered.

It looks something like this ...
http://farm3.static.flickr.com/2023/2183255937_ee2ffb7d96.jpg

- Franc Zabkar

 

Also true of a dirty head for the most part with possible left right
issues.
A magnetized head can ruin tapes HF.

Greg

 

Much of the audible 'squeek' noise may be the fault of the housing,
rather than the tape itself. Transfering the reels to a new case may
fix that. Labels can also be transfered, if the fix works.

In some instances, the case was defective on first transfer, so the
audible jitter was included in that transfer - no way around this.

RL

 

You mention the capstan, I would also check the rubber roll very
carefully. After years it often gets little tears in the rubber and it
may be deformed and therefor not be guiding the tape correctly anymore.
They are cheap and relatively easy to replace.

Greetings,
Rene