I had two cassette tapes (one owned by me, one owned by a client) that just wouldn't play in any of
my tape decks. In both cases, I had tried re-shelling and even replacing the reels because I've
heard of cases where the reels warp or otherwise get where they don't fit well in the drive stalks.
Obviously, since I could replace the reels, both tapes fast-wound just fine. But with playback, both
tapes would play a few minutes and then slow down and then the auto-stop mechanism would kick in
because there was too much tension. Tapping the cassettes to loosen the tape-slip mat contact didn't
help. Richard Hess suggested, "try baking them," noting that he had fixed unplayable DAT tapes by
baking. So I tried 4 hours in the American Harvest dehydrator.
The tape I owned (an unknown-brand duplicated tape that says made in Canada on the outer package,
with a copyright date of 1984) played just fine, made it through both sides with no problems and
excellent audio quality. The client's tape (a 1977 vintage Ampex Plus Series C-90) made it through
side 1 just fine and made it through 35 minutes of side 2. Then, it started squealing loudly, and
the squealing was audible on playback, so it was a "bow string" kind of squealing across the heads.
I stopped playback, rewound to before where the squealing began, ejected the tape, cleaned the heads
and the tape path with isopropynol, and vigorously tapped the cassette housing on the table to
loosen up the tape pack and the tape-slip pad contact. I then put it back in and it played back the
last part of side 2 just fine. An hour or two later, I attempted to rewind to the same place and
play it and no matter what I did, the tape squealed worse than before. My theory is that I didn't
bake that tape long enough and it very quickly started going back to sticky. Next time, I will try
8-hour baking. For what it's worth, baking did not seem to harm the generic cassette shells I used
nor to melt the end-of-side splices to leader tape.
I know that the operating theory on traditional sticky-shed requires the tape to be back-coated, so
I do not know if this problem is sticky-shed or something else cured by dry heat. Whatever the case,
I have a few more circa 1980s generic duplicator-tape cassettes that will not playback right now,
and I intend to try baking. I will report back.
Also for what it's worth, there was no brown oxide-like residue on the head-cleaning swabs for
either baked tape. I still do not know what caused the squealing, and no visible residue came off
the heads or tape path (this doesn't mean that some sort of clear goo or a sticky liquid wasn't
Has anyone else had success baking cassettes that wouldn't playback otherwise? Do you remember what
type(s) of cassettes they were? Their approximate time of manufacture? I'm wondering if we can zero
in on certain problem cassette types. I don't think this is nearly as common as in reel tapes, based
on my experiences transferring 1000+ cassettes of every era (from the 60s dawn of Compact Cassettes
to very recent vintage). These two cassettes, plus a handful more in my personal collection, are the
only tapes that ground to a halt in all of my tape decks and couldn't be fixed by re-shelling.
-- Tom Fine