Someone please email me (and post here if you like) if you have an idea
about this problem which has been driving me NUTS the last couple of days...

Friday I got a rare collectible recording that is only available on
cassette. (Ithis was EXTREMELY rare, and that, for starters, limits my
options.) I quickly found that it would not play at a steady speed--it keeps
slowing up. I played it through in both directions, and it keeps slowing up.
My cassette deck does fine with other tapes. I put this tape in my car
player, and it immediately ejected it. So obviously there's something wrong
with this tape--but I can't see what!

The condition of the tape looks all right. The case looks all right, except
that there is a slight split in the front part of the case--less than a
millimeter, I'd say, and it looks even and regular, not like it's been
mangled or anything. I don't notice dropouts, and the noise, distortion,
frequency response, etc. seem normal. There is a little bit of crosstalk
from the reverse tracks, but no worse than I've heard on many other
cassettes. There does not appear to be any resistance to turning the reels,
not do I hear any unusual mechanical noises when playing the tape.

What could possibly be wrong?! And what sort of person might I want to
approach to diagnose and "fix" this cassette, if I can't do it myself?

--Ronald W. Garrison

It should be possible to put the tape pack in another shell. Often helps in
this situation, but not guaranteed. The tape pack itself could be sticking
from migrated adhesive.

Mark Z.


"RWG" wrote in message
...
Someone please email me (and post here if you like) if you have an idea
about this problem which has been driving me NUTS the last couple of
days...

Friday I got a rare collectible recording that is only available on
cassette. (Ithis was EXTREMELY rare, and that, for starters, limits my
options.) I quickly found that it would not play at a steady speed--it
keeps slowing up. I played it through in both directions, and it keeps
slowing up. My cassette deck does fine with other tapes. I put this tape
in my car player, and it immediately ejected it. So obviously there's
something wrong with this tape--but I can't see what!

The condition of the tape looks all right. The case looks all right,
except that there is a slight split in the front part of the case--less
than a millimeter, I'd say, and it looks even and regular, not like it's
been mangled or anything. I don't notice dropouts, and the noise,
distortion, frequency response, etc. seem normal. There is a little bit of
crosstalk from the reverse tracks, but no worse than I've heard on many
other cassettes. There does not appear to be any resistance to turning the
reels, not do I hear any unusual mechanical noises when playing the tape.

What could possibly be wrong?! And what sort of person might I want to
approach to diagnose and "fix" this cassette, if I can't do it myself?

--Ronald W. Garrison

"Mark D. Zacharias" wrote in message
...
It should be possible to put the tape pack in another shell. Often helps in
this situation, but not guaranteed. The tape pack itself could be sticking
from migrated adhesive.


Yes, and it might come to that. (I didn't see any indication of crud on the
tape, although that may not be any guarantee of anything.)

--Ronald W. Garrison

In article , Mark D. Zacharias
wrote:

It should be possible to put the tape pack in another shell. Often helps in
this situation, but not guaranteed. The tape pack itself could be sticking
from migrated adhesive.

I have seen situations where the tape was not wound on the spools
in an even manner. In this case, doing a few fast-forwards and
rewinds might do the trick. Otherwise, I think Mark has the
solution. The slip-sheets inside of the cassette might have
dried out, and it adds just enough drag to cause problems on
playback. Radio shack has replacement shells, or use any cassette
tape where the case uses screws (as opposed to sonic welds).

-john-

--
================================================== ==================
John A. Weeks III 952-432-2708
Newave Communications http://www.johnweeks.com
================================================== ==================

I have seen situations where the tape was not wound on the spools
in an even manner. In this case, doing a few fast-forwards and
rewinds might do the trick. Otherwise, I think Mark has the
solution. The slip-sheets inside of the cassette might have
dried out, and it adds just enough drag to cause problems on
playback. Radio shack has replacement shells, or use any cassette
tape where the case uses screws (as opposed to sonic welds).

Thanks, I hadn't thought about the slip sheets. I may just go ahead and do
the re-spooling. It should be safe, if done with reasonable care. I just
hate to take apart the case on a collectible--it was extremely rare, and
very expensive.

There might be one other possibility, though: Suppose there is a problem
with the pinch roller/capstan grip. My deck is, I'm pretty sure, a
single-motor type. Don't some of the more expensive decks have a way of
setting them so that the reels will control the speed, so that you aren't
even relying on the capstans? Then that might solve the speed problem.

I only care about recording this once, to record it into my sound card.
After that, it can sit on the shelf.

--Ron

In article , RWG
wrote:

There might be one other possibility, though: Suppose there is a problem
with the pinch roller/capstan grip. My deck is, I'm pretty sure, a
single-motor type. Don't some of the more expensive decks have a way of
setting them so that the reels will control the speed, so that you aren't
even relying on the capstans? Then that might solve the speed problem.

You really cannot use the reels on a cassette to control the speed
since the take-up reel gets bigger as the tape plays, so it will speed
up the tape. The capstan is there specifically to ensure a
constant playback speed.

You should try this tape in yet another tape deck, just to be sure.
I kind of ruled out tape decks since you had two decks that didn't
like the tape.

-john-

--
================================================== ==================
John A. Weeks III 952-432-2708
Newave Communications http://www.johnweeks.com
================================================== ==================

In article ,
"RWG" wrote:

Someone please email me (and post here if you like) if you have an idea
about this problem which has been driving me NUTS the last couple of days...

Friday I got a rare collectible recording that is only available on
cassette. (Ithis was EXTREMELY rare, and that, for starters, limits my
options.) I quickly found that it would not play at a steady speed--it keeps
slowing up. I played it through in both directions, and it keeps slowing up.
My cassette deck does fine with other tapes. I put this tape in my car
player, and it immediately ejected it. So obviously there's something wrong
with this tape--but I can't see what!

The condition of the tape looks all right. The case looks all right, except
that there is a slight split in the front part of the case--less than a
millimeter, I'd say, and it looks even and regular, not like it's been
mangled or anything. I don't notice dropouts, and the noise, distortion,
frequency response, etc. seem normal. There is a little bit of crosstalk
from the reverse tracks, but no worse than I've heard on many other
cassettes. There does not appear to be any resistance to turning the reels,
not do I hear any unusual mechanical noises when playing the tape.

What could possibly be wrong?! And what sort of person might I want to
approach to diagnose and "fix" this cassette, if I can't do it myself?

--Ronald W. Garrison

Just throwing out random suggestions -


If the crack is at the seam, a pinched tape guide may be holding it
open. Pry open the crack a bit more, wiggle it, then try to seat it so
it closes fully.

If the crack is near the spools, you may have to transfer the spools to
a new shell. Some audio shops may still sell replacement shells that
are held together with screws.

John's suggestion is very good. The drop that caused the crack may have
shifted the spools so they rub.

The tape could be sticky or oily. A shop may have something to fix that.

You really cannot use the reels on a cassette to control the speed
since the take-up reel gets bigger as the tape plays, so it will speed
up the tape. The capstan is there specifically to ensure a
constant playback speed.

You should try this tape in yet another tape deck, just to be sure.
I kind of ruled out tape decks since you had two decks that didn't
like the tape.

I know it's kind of a long shot, but I could picture a sophisticated enough
system could monitor the relative speeds of the two reels, and compute the
proper speed to deliver 4.75 mm/sec between the reels. But I've not
investigated whether anyone makes such a deck. Another possibility BTW, IF
you could get the capstans to actually stay out of the way, would be to find
a digital editor which would apply just the right constantly varying speed
correction. Again, I don't know how hard this is to implement.

It might indeed be worth trying another tape deck first!

If the crack is at the seam, a pinched tape guide may be holding it
open. Pry open the crack a bit more, wiggle it, then try to seat it so
it closes fully.

I know what you're thinking, but it doesn't look to me like there is
anything pushing it open from the inside. It's barely open, as though
there's nothing really holding it sealed, as it looks like with other
cassettes.

I'm inclining more and more to the slip-sheet-sticking theory.
Unfortunately, confirming that would probably require prying open the molded
shell (no screws, too bad), so I'll probably never know for sure. I'll
probably wind up just winding it into a new case, by cutting the tape at the
end and running it out---unless I can find some other solution.

If the crack is near the spools,

No, it isn't. It's at the front.

you may have to transfer the spools to
a new shell. Some audio shops may still sell replacement shells that
are held together with screws.

I'm pretty condifent even Radio Shack will have one of those. Hope so,
anyway.

The tape could be sticky or oily. A shop may have something to fix that.

I don't see any sign of crud on the tape that would suggest that, which is
good, because if this turns out to true that's probably a much more
difficult problem. At that point, I think I'd be back to trying to make a
capstan-less solution.

"RWG" wrote ...
I don't see any sign of crud on the tape that would suggest that, which is
good, because if this turns out to true that's probably a much more
difficult problem. At that point, I think I'd be back to trying to make a
capstan-less solution.

A "capstan-less solution" seems like the very least likely to work.
Even under prinstine laboratory conditions it would be nearly
impossible to maintain accurate and even tape speed using
only the reels. Tape recorders that used "rim-drive" were
toys at the very bottom of the heap. And Philips likely never
licenced any Compact Cassette equipment that used "rim-drive"

There was once an Ampex recorder that sucked the tape out
of the shell into a big vacuum chamber with a big rubber-
covered capstan in the middle. The vacuum held the tape
against the heads which were on either side of the capstan.
It was actually an adaptation of the old computer tape drives
(the big ones with 1/2 inch tape on 10.5 inch reels that you
see in old movies.)

It was optimized for high-speed in-shell duplication, but it
apparently never made it into production as I've never seen
one except at the AES convention in LA in the mid 1970s.

In article , Richard Crowley
wrote:

"RWG" wrote ...
I don't see any sign of crud on the tape that would suggest that, which is
good, because if this turns out to true that's probably a much more
difficult problem. At that point, I think I'd be back to trying to make a
capstan-less solution.

A "capstan-less solution" seems like the very least likely to work.
Even under prinstine laboratory conditions it would be nearly
impossible to maintain accurate and even tape speed using
only the reels.

That acutally sounds like an interesting engineering problem.
One solution that I see would be to record a control track on
the tape with a certain frequency sine wave. Or series of
pulses. This could be used as part of a servo-loop that controls
the motors. If the wave drops in frequency on playback, then
speed up the motor, and vice versa. Another way would be to
use some kind of variable time-delay to selectively delay
different parts of the playback by differing amounts of time to
bring the control channel wave back to the right frequency.

-john-

--
================================================== ==================
John A. Weeks III 952-432-2708
Newave Communications http://www.johnweeks.com
================================================== ==================

"John A. Weeks III" wrote in message
...
In article , Richard Crowley
wrote:

"RWG" wrote ...
I don't see any sign of crud on the tape that would suggest that, which
is
good, because if this turns out to true that's probably a much more
difficult problem. At that point, I think I'd be back to trying to make
a
capstan-less solution.

A "capstan-less solution" seems like the very least likely to work.
Even under prinstine laboratory conditions it would be nearly
impossible to maintain accurate and even tape speed using
only the reels.

That acutally sounds like an interesting engineering problem.
One solution that I see would be to record a control track on
the tape with a certain frequency sine wave. Or series of
pulses. This could be used as part of a servo-loop that controls
the motors. If the wave drops in frequency on playback, then
speed up the motor, and vice versa. Another way would be to
use some kind of variable time-delay to selectively delay
different parts of the playback by differing amounts of time to
bring the control channel wave back to the right frequency.

Philips CompactCassettes were used with "rim-drive" for
digital recording where, inded the data is "self-clocked"
(like the mag strips on our credit cards).

OTOH, with a traditionally-recorded analog cassette, there
is no reference unless you wanted to use some sort of laser
optical device like an optical mouse uses.

In article ,
"RWG" wrote:

You really cannot use the reels on a cassette to control the speed
since the take-up reel gets bigger as the tape plays, so it will speed
up the tape. The capstan is there specifically to ensure a
constant playback speed.

You should try this tape in yet another tape deck, just to be sure.
I kind of ruled out tape decks since you had two decks that didn't
like the tape.

I know it's kind of a long shot, but I could picture a sophisticated enough
system could monitor the relative speeds of the two reels, and compute the
proper speed to deliver 4.75 mm/sec between the reels. But I've not
investigated whether anyone makes such a deck. Another possibility BTW, IF
you could get the capstans to actually stay out of the way, would be to find
a digital editor which would apply just the right constantly varying speed
correction. Again, I don't know how hard this is to implement.

It might indeed be worth trying another tape deck first!

I've heard traces of a bias signal when playing back some commercial
tapes at low speeds. That could, in theory, be used to digitally
reconstruct a perfectly timed playback. The bandwidth of the sampling
rate would have to be very large, though. You'd probably need 24
bits/channel with a 192KHz sampling rate to find that faint tone in a
tape wobbling along with no capstan. 16 bits sampled at 96KHz might
work if the tape was slowed down and the signal got a good amount of
analog enhancement.

It's probably not worth the effort. Any tension on the reels crushes
the inner windings. It would be something you'd do to make a copy
before throwing the tape out. The original bias frequency might not
always be constant either.

Hello,

I would not do your method of cutting the tape and winding it out. I'd
suggest splitting open the case and transferring both reels to a new
shell. Get a screwed together cassette, open it, and remove the reels
and then put them back in to get a feel for the procedure before trying
this on your valuable tape.

For curiosities sake, if you don't mind telling, what is the recording
of?

Regards,
Tim Schwartz
Bristol electronics

RWG wrote:

If the crack is at the seam, a pinched tape guide may be holding it
open. Pry open the crack a bit more, wiggle it, then try to seat it so
it closes fully.

I know what you're thinking, but it doesn't look to me like there is
anything pushing it open from the inside. It's barely open, as though
there's nothing really holding it sealed, as it looks like with other
cassettes.

I'm inclining more and more to the slip-sheet-sticking theory.
Unfortunately, confirming that would probably require prying open the molded
shell (no screws, too bad), so I'll probably never know for sure. I'll
probably wind up just winding it into a new case, by cutting the tape at the
end and running it out---unless I can find some other solution.

If the crack is near the spools,

No, it isn't. It's at the front.

you may have to transfer the spools to
a new shell. Some audio shops may still sell replacement shells that
are held together with screws.

I'm pretty condifent even Radio Shack will have one of those. Hope so,
anyway.

The tape could be sticky or oily. A shop may have something to fix that.

I don't see any sign of crud on the tape that would suggest that, which is
good, because if this turns out to true that's probably a much more
difficult problem. At that point, I think I'd be back to trying to make a
capstan-less solution.

I recommend not attempting to play the tape in its current condition.
The shell is pinching the tape and the risk of edge damage is high.
While not likely on an older deck, if the take-up tension is high
enough, you also risk stretching the tape .

It's relatively easy to transfer a tape pack to a new shell. Since the
tape in question is so valuable, practice on a few junk tapes first.

-----------------------------------------------------------
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wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15
13 (Barry Mann)
[sorry about the puzzle, spammers are ruining my mailbox]
-----------------------------------------------------------

I've heard traces of a bias signal when playing back some commercial
tapes at low speeds. That could, in theory, be used to digitally
reconstruct a perfectly timed playback. The bandwidth of the sampling
rate would have to be very large, though. You'd probably need 24
bits/channel with a 192KHz sampling rate to find that faint tone in a
tape wobbling along with no capstan. 16 bits sampled at 96KHz might
work if the tape was slowed down and the signal got a good amount of
analog enhancement.

It's probably not worth the effort. Any tension on the reels crushes
the inner windings. It would be something you'd do to make a copy
before throwing the tape out. The original bias frequency might not
always be constant either.

I don't think that would work all that well, would probably leave some
significant speed error, and IAC is probably not necessary. (It's an
intriguing idea, though, and might be doable--it would never have occurred
to me.) If you have a way of monitoring the size of the tape pack and the
speed of the reels, you can probably work it out. In fact, if you know the
maximum and minimum sizes of the tape pack, and the duration of the tape at
1.875 ips, you should be able to calculate how the takeup reel speed should
vary over the course of playback. You would just need to apply enough torque
to the feed reel to maintain a small, constant tension, and control
everything with the takeup reel.

There are two ways you could do that. Theoretically (as all this is really,
I'm sure you realize!), you could rig the tape machine to follow such a
speed profile, adjusting the takeup reel speed to keep the tape speed at the
head a constant 1.875 ips. OR you could just take up the tape at some
constant speed, and apply the corrections later in a digital editor.
However, you would have to also vary equalization over the course of the
playback. But again, I'd rather tackle working out some filtering curves for
a digital editor than sit and try to modify the mechanical and electronic
inner workings of a tape deck. I'm sure most others will feel the same.

But back to the real world, I think tonight I'm going to have a nice dinner,
get settled in and get my thoughts focused, and carefully work on winding
this tape from the existing shell to a new one. If that doesn't work, I
don't know what to do.

"Kevin McMurtrie" wrote in message

In article ,
"RWG" wrote:

You really cannot use the reels on a cassette to control the speed
since the take-up reel gets bigger as the tape plays, so it will
speed up the tape. The capstan is there specifically to ensure a
constant playback speed.

You should try this tape in yet another tape deck, just to be sure.
I kind of ruled out tape decks since you had two decks that didn't
like the tape.

I know it's kind of a long shot, but I could picture a sophisticated
enough system could monitor the relative speeds of the two reels,
and compute the proper speed to deliver 4.75 mm/sec between the
reels.

This has been done with tapes operating in the digital domain.

But I've not investigated whether anyone makes such a deck.

As a product, I doubt it. The last new idea in cassette decks that I heard
of involved using DSP signal processing to compensate for amplitude-domain
issues. Prototypes were reported, but nothing seems to have made it to
market.

Another possibility BTW, IF you could get the capstans to actually
stay out of the way, would be to find a digital editor which would
apply just the right constantly varying speed correction. Again, I
don't know how hard this is to implement.

Something like this has been done in the context of recovering good sound
from defective analog master tapes.

It might indeed be worth trying another tape deck first!

I've heard traces of a bias signal when playing back some commercial
tapes at low speeds. That could, in theory, be used to digitally
reconstruct a perfectly timed playback.

That was done in the technology I just mentioned.

The bandwidth of the sampling
rate would have to be very large, though. You'd probably need 24
bits/channel with a 192KHz sampling rate to find that faint tone in a
tape wobbling along with no capstan.

Note - you can roll the tape as slowly as you want, if you use a modified
deck. This would move the bias frequency down to something that you could
easily recover with conventional heads and playback electronics.

It's relatively easy to transfer a tape pack to a new shell. Since the
tape in question is so valuable, practice on a few junk tapes first.

Well, I've done it, by the spooling it reel-to-reel by hand, without opening
the original case; and the results worked well, except that the tape pulled
loose from the hub at each side change. (But that didn't stop me from
ripping the audio, which is what I really cared about.) Looking back on it,
I do think this was the best way to go, of all the alternatives (at least
all the ones that didn't involve a whole research project). But I wouldn't
call it exactly "easy." You need to choose a time when your nerves are
steady, and to give this your undivided attention.

Thanks to all for your discussion and recommendations. Even if your solution
was not the one that worked for me, it stimulated creative thinking on my
part, and helped me to get to success.

--Ronald W. Garrison

"RWG" wrote ...
It's relatively easy to transfer a tape pack to a new shell.
Since the tape in question is so valuable, practice on a few
junk tapes first.

Well, I've done it, by the spooling it reel-to-reel by hand, without
opening the original case; and the results worked well,.....

Thanks to all for your discussion and recommendations. Even if your
solution was not the one that worked for me, it stimulated creative
thinking on my part, and helped me to get to success.

Just curious why you rejected the method of opening the original
shell and just transfering the reels to a screw-together shell?

IMHO, subjecting such fragile tape (particularly a valuable copy)
to manual spooling is more dangerous than transfering the whole
reels.

Just curious why you rejected the method of opening the original
shell and just transfering the reels to a screw-together shell?

Because it would have required destoying the original case, which was not
screwed together but apparently put together with some kind of
plastic-welkding process. I wasn't even sure where the weld points were.

IMHO, subjecting such fragile tape (particularly a valuable copy)
to manual spooling is more dangerous than transfering the whole
reels.

Oh tell me about it! As I said, it was quite tricky to do, with the tape at
times wanting to flop all over the place. I got the tape started, then put
the shell together and spooled from one closed shell to another. (It took
about as long as playing the tape would.) Then I opened the case again,
carefully so as not to disturb the tape any more than necessary, and hooked
up the other reel, and put it back together.

Worse, the tape was recorded right up to the end of the tape at a couple of
points, with no leader. Fortunately, I recorded those same stretches
previously, and I don't think they have any wow problems in those regions. I
also have a second-hand copy that someone loaned me years ago and I
digitized, so I can fall back on that if there are any dropouts. In fact,
there is a small one in the middle of the tape (not due to handling) that I
may wind up fixing using the old copy.

Just curious why you rejected the method of opening the original
shell and just transfering the reels to a screw-together shell?

"RWG" wrote ...
Because it would have required destoying the original case, which was not
screwed together but apparently put together with some kind of
plastic-welkding process. I wasn't even sure where the weld points were.

Usually just spot welded in a few places. You can frequently pop
them apart with a good sharp knife. Even if they are welded all the
way around a Dremel tool with a tiny saw blade will do a very
smooth job of splitting it open. Even if you have to saw it apart,
still preferable to manually spooling from one shell to another,
at least IMHO.