Sometimes depended on brand and quality of original cassette, and how
much it has been abused through the years.  Likely culprit is piece of
polyester film between tape cams and outer body of cassette.  A dry
lubricant was placed on the sides of films toward the tape cams.  Some
mfrs used cheap lube, some none at all (think 3 for a $1 specials), some
may have used different material to perform this function (stopped
taking my dead tapes apart somewhere in the early 80s).  High-end mfrs,
like 3M and BASF, used better grade of lubricant.  Sometimes the
lubricant would fail because of constant use.

Thanks for the trip down memory lane...! 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bill Campbell
Sent: Thursday, December 18, 2008 11:55 AM
To: [log in to unmask]
Subject: Re: [TN] Way off-topic: CrO2 cassette tape

As long as we're a little off topic: Does anyone know why sometimes
cassettes develop a high pitched mechanical squeak?  Also if there's a
fix?
I have a few tapes that have this but would love to save long enough to
convert to newer formats.

On Thu, Dec 18, 2008 at 9:28 AM, Simonik, Dave R. (David) <
[log in to unmask]> wrote:

> From http://en.wikipedia.org/wiki/Cassette_tapes
>
> Cassette tapes are made of a polyester type plastic film with a 
> magnetic coating. The original magnetic material was based on gamma 
> ferric oxide (Fe2O3). Circa 1970, 3M Company developed a cobalt 
> volume-doping process combined with a double-coating technique to 
> enhance overall tape output levels. This product was marketed as "High

> Energy" under its Scotch brand of recording tapes.[14] Inexpensive 
> cassettes are commonly labeled "low-noise", but typically are not 
> optimized for high frequency response.
>
> At about the same time chromium dioxide (CrO2) was introduced by 
> BASF,[15] and then coatings using magnetite (Fe3O4) such as TDK's 
> Audua were produced in an attempt to approach the sound quality of 
> vinyl records. Cobalt-absorbed iron oxide (Avilyn) was introduced by 
> TDK in
> 1974 and proved very successful. Finally pure metal particles (as 
> opposed to oxide formulations) were introduced in 1979 by 3M under the

> trade name Metafine. The tape coating on most Cassettes sold today as 
> either "Normal" or "Chrome" consists of Ferric Oxide and Cobalt mixed 
> in varying ratios (and using various processes); there are very few 
> cassettes on the market that use a pure (CrO2) coating.
>
> Dave Simonik
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
> Sent: Thursday, December 18, 2008 10:07 AM
> To: [log in to unmask]
> Subject: Re: Way off-topic: CrO2 cassette tape
>
> Craig,
> Assuming all the Cr there is indeed in the form of CrO2, then whether 
> it falls under RoHS is immaterial, as the Cr is present in the +4 
> oxidation state, not +6.
> Bev
> RIM
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Craig Cullum
> Sent: Thursday, December 18, 2008 10:04 AM
> To: [log in to unmask]
> Subject: [TN] Way off-topic: CrO2 cassette tape
>
> Hi all,
> We're expecting a huge snowfall overnight and tomorrow and have been 
> advised not to come to work.
> So . . . for me it feels like Friday, and here's my question:
>
> Do all my old metal-oxide cassette tapes, specifically the chromium 
> CrO2 tapes, fall under RoHS regulations?
> Hypothetically, if I was in Europe, how would I safely dispose of 
> these tapes?
>
> Just wondering.
>
> Craig Cullum, Engineering Technologist, AMTELCO
> e: [log in to unmask]
>   [log in to unmask]
> f: 608 838 8367
> v: 608 838 4194, or 4197, x128
>
> Please visit us at www.amtelco.com
>
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