Tape movement

This is a view of the cartridge
with the top removed.  It is
oriented as if you had just
inserted it into your player.

When you insert the tape, the
capstan in the machine (a
rotating steel post about 1/4" in
diameter) presses against the
ROLLER, turning it clockwise
which then pulls tape from the
center of the reel.

This action also causes the HUB
to rotate clockwise, which in
turn takes up the "used" tape
onto the outside of the reel.  In
this fashion, a tape will play
continuously, never stopping.

This is a fine arrangement, but
is mathematically impossible.

However, a few little tricks
make it such that the laws of
Physics can be fooled, which
unfortunately means you will
need to do some babysitting.

The first problem:
The problem is that we are trying to remove, then replace tape - onto objects with
different diameters (i.e., the inside and outside of the reel).  Let's say the hub is 1.5
inches in diameter, and the outside of the reel is 2.5 inches in diameter.

Using the simple math formula for circumference (3.14 X diameter), we can then say
the circumference is equal to a length of tape.  So, for each revolution of the hub, we
are pulling 4.71 inches of tape out, but the outside of the reel is actually pulling 7.85
inches of tape back on.  And this is a short tape.  If it were a bit longer, it would be
taking up more than TWICE AS MUCH tape as it was giving out!

Obviously, this is impossible without doing a little head-scratching and cheating.  In a
very short time, the tape would be wound so tightly that it would refuse to move.
The first solution:
In order for this scheme to work, the tape needs to be able to SLIDE between layers,
and also slide on the hub.  This prevents the tape from binding and being wound
too tightly.  The tape is wound somewhat loosely during manufacture, and is also
treated with a lubricant - usually graphite.

You'll see a silvery band on your tape rollers - this is graphite lubricant.
You must always keep your tape rollers clean, and free of this lubricant !
The second problem:
As you may have guessed by now, having graphite on your rollers (and thus the
capstan in your machine) is very much like going out to your car, raising the hood and
pouring oil on all your drive belts.  Long story short, they won't grip like they need to,
and your car won't run properly for very long.  

By the same token, your machine won't grip the rollers properly.  This results in
dragging, speed variations, or no tape movement at all.  Since this is inherent in the
design of the 8 track format (the only tape format that has this flaw), it is not a defect
of recent repairs (especially by me!), but is rather a minor maintenance procedure
that must be performed by all owners and users of 8 track machines and tapes.
The second solution:
Basically, anything that is supposed to grip needs to be clean and free of any type of
oil, grease or graphite buildup.  This means keeping your tape rollers clean, as well
as the capstan inside your machine.  Thankfully, the capstan can be seen (and
usually reached) through the tape door.  Simply push that door in and peek into the
back.  The capstan, a vertical steel post about 1/4 inch wide, can be seen to the right
of the playback head.  If you have small hands, you can sometimes poke a finger
through an old T shirt, dip it in household alcohol and reach it that way.


Since you need to clean the entire capstan (not just the part that currently faces the
front of the machine), you need some way to expose all sides for cleaning.  One way
to do this is to insert a tape and let it play a few seconds, which will hopefully expose
a different area to clean.  Do this several times - and with luck, you'll eventually get
the entire capstan cleaned.

BE EXTREMELY CAREFUL not to disturb or break anything inside the tape door.  On
most models, there are some brass leaf switches that must not be bent, or other
mechanical surprises that can be harmed by rough handling.  If the capstan is too
deep in the machine, you'll need to be a bit more creative on how to reach back there.
A long stick with a small wad of cloth tied to the end, etc.  Unfortunately, long Q Tips
are generally not strong enough to apply any useful force - bummer!

An EXCELLENT tool to use is an 8 track tape with the roller removed, and replaced
by a wad of cloth.  Simply soak the wad with alcohol, pop the tape in for a minute or
two, and the capstan will automatically turn against the cloth and clean itself!  This
will work as a routine cleaning procedure, but still will not remove years of built-up
gunk or layers of tape that got sucked up by a dirty or sticky capstan.  This type of
repair requires a professional.

Keep in mind that TOO much alcohol will seep down onto the capstan bearings and
dilute any lubricant that it needs to avoid excessive wear.  So, soak the wad of cloth
but not to the point that it will squeeze out and drip when put under pressure.

You also must keep the rollers on your tapes clean.  You can generally do this by
carefully moving the tape aside using tweezers, then use a cloth dipped in RUBBER
CLEANER to clean the rollers until they are black again.  Alcohol will dry out rubber,
but is safe for plastic rollers.  When finished, wipe off any excess rubber cleaner - it is
slippery while still in liquid form.  Alcohol will evaporate just fine by itself.
tape is
up on
of the
Track Switch       Playback Head          Capstan
rotates CCW,
turning roller
and hub CW
Track change switch
Playback head
Let's open the door and look inside:
You must always keep your tape rollers clean, and free of this lubricant
You don't have to take the tapes apart to clean the rollers
Keep in mind that almost ALL 8 track tapes will need a NEW foil splice and pressure
pad before they will play properly.  Always check your player with a known good,
RECENTLY REPAIRED tape before determining the need for professional service
the foil
to come
off due
to its
NOTE:  Properly maintained, 8 track machines do not eat tapes!  This is caused by breakage
of the foil splice on the tape itself.  It is absolutely essential that any 8 track tape has a new
foil splice and pressure pad before attempting to play it.  To understand why, see the yellow text
box in the upper left corner of the above illustration.   We also offer quality TAPE REPAIR.
4783 N. Glenrosa Circle
Prescott Valley, AZ  86314

E-mail:  Barry8Track@cableone.net