Call  928-533-9666 (Paying Repair Jobs ONLY)
DO NOT CALL FOR BELTS, PARTS OR FREE REPAIR ADVICE!
Converting Delco Separate-Component Systems
Delco systems in which the 8 track unit is separate from the radio are a special case requiring special
considerations, as well as a substantial amount of extra work to gain maximum performance.  Without
getting too complicated, here is the general rundown on the system limitations and corrective measures.
Limitations on a Converted System Due to Original System Layout

To allow for easy expansion of the sound system and flexibility to work with all possible customer choices - that is, a mono AM radio, a
mono FM radio, a mono FM radio with a multiplex adaptor to make it stereo, or a straight stereo AM-FM radio - Delco made almost all
of their 8 track players with their own independent speaker amplifiers, then the 8 track could easily be added to any of their existing
sound systems by using a different wiring harness between the car wiring, existing radio and 8 track player.  Especially for years 1967
through 1969, the many possible systems available were confusing enough to make one's head spin.

To make a long story short, the addition of an 8 track player to the system resulted in a switching configuration that can be very
confusing to someone not familiar with these specific systems.  Now, the speakers were "normally" connected directly to the  8
track player, as well as 12 volt power.  Inside the 8 track unit is a massive switch which is actually four dual-position switches in one.
You'll see this switch in the pictures below; it's the round device with 12 terminals next to the filter choke.  This switch controls at
least three separate functions:  Left speaker switching, right speaker switching and 12 volt power switching between the radio and
8 track players, depending on whether there is a tape inserted in the 8 track player.  Refer to the simplified system layout shown here:
Without a tape inserted, the multi-function switch is in the position to simply pass the output from the radio to the speakers, and also
to send the 12 volt power
to the radio so that it can operate through the speakers.  When a tape is inserted, the switch changes its
position, and now connects the speakers to the 8 track's output amplifiers while it also transfers the 12 volt power to the 8 track unit.

Even though this arrangement results in a somewhat crazy zip-zapping of signals and voltages back and forth, it worked just fine as
far as the requirements of the current system electronics and user-friendliness are concerned.  But - please keep reading.


Problems With This Type of System AFTER Converting the Radio
(That is, assuming you want the 8 track to also play through the new amplifiers)
As I just mentioned, the system worked fine
with the ORIGINAL electronics.  But with
the increased audio power and enhanced
fidelity of the radio after conversion, the
fact that the tape head preamplifier and the
motor control circuitry are very close to
each other presents a slight problem.

The motor control circuitry and the tape
head preamp circuitry are highlighted to
illustrate their close proximity to each other.
This causes noise and static from the motor
circuitry to radiate into the tape preamps,
which can be distinctly heard through the
speakers during quiet music passages.

Even though the actual preamp circuits are
mostly at the bottom left corner, the wiring
extends all the way to the volume control,
and thus is included in the highlighting.

This was not a problem with the original
electronics, but now it IS a problem due to
the increased audio power and higher
fidelity of the converted audio system.
( More power and fidelity = MORE NOISE )
Radiation of Motor Noise

Before I go further with this rant, I will say that this is NOT a problem if the customer chooses to leave the 8 track player "as is",
and have the conversion upgrade apply ONLY to the radio, since the 8 track player does have its own speaker amplifiers.  
BUT -
the radio conversion MUST BE SET UP FOR A COMMON-GROUND SPEAKER SYSTEM, which reduces its output power and
results in less-than-optimum performance.   COMMON-GROUND SPEAKER OUTPUTS
CANNOT BE USED IN THE SAME SYSTEM
WITH ISOLATED SPEAKER OUTPUTS - THIS WILL CAUSE PERMANENT DAMAGE TO THE ISOLATED-GROUND RADIO !!!  Thus,
the solution for best sound and maximum audio power can only be gained by performing this modification to this 8 track player.
Motor Control
Circuit
Tape Head
Preamp
Circuits
Mainly just for fun, I'm also including a picture
of the top side of the 8 track player before I
butcher the heck out of it.  The round multi-
function switch mentioned earlier can be seen
near the controls, motor and filter choke.

Get a good look now, because there won't be
nearly as much left in the unit after I work my
magic on it.  The  2 cables from the tape head
can be seen on the right side, and the tiny
signal from the head ends up going to a lot
of places it really doesn't need to - and this
allows the high-gain preamp circuitry to pick
up a lot of noise from many sources.

Since installing a modern conversion calls for
a complete gutting of the radio to make way
for the new electronics, we might as well do
a complete teardown and modern rebuild on
the 8 track player also.  This eliminates
more
than 100 old parts
which could eventually fail
and/or cause trouble in the future, and most
parts required for operation will be
brand new.
Are You Sitting?  It Might be Best, Because Here is Your Rebuilt 8 Track Unit !
"Holy cow, where is everything?"

This IS everything !  We no longer need the
heat-generating output amplifiers since the
converted radio supplies them.  Actually, we
don't even need the two output transformers
on the right side; I was simply too lazy to
remove them - they are not connected.

The tiny hand-built circuit board at bottom
left is your NEW tape head preamplifier -
located as far as possible from the NEW,
hand-built motor speed control board which
you will see in the next picture.  The preamp
output wires are routed away from anything
that can generate noise.  The original motor
pulley has been removed and pressed onto
the shaft of the NEW motor, using our 12-ton
shop press that we have just for this purpose.

New motor - new capstan surface - new tape
head preamp -
who could ask for more ?
This picture of the top side shows how far the
NEW motor speed control board is from the
NEW tape head preamp board (located on the
bottom side).  The 8 track unit is relieved of
everything it no longer needs, and which can
cause noise or fail causing other problems.

Not shown at this stage is the wiring of the
external Line In jack, which will simply connect
to the multi-function switch to allow for the
automatic switching between 8 track tape and
Line Input function depending on whether a
tape is inserted or removed from the unit.

Also, the confusing 8 track connector has been
eliminated from the wiring harness because
the system signal routing has been made much
more sensible and easier for the car owner to
troubleshoot should it ever be necessary.

The 8 track will connect to the radio using RCA
cables, and it's all controlled from the radio now.
In this particular arrangement, the controls on the 8 track unit are now only for original appearance, and all
functions except the track change switch are now controlled from the converted radio.  If desired, the volume
and balance controls can still be wired into the 8 track, with slightly different functions.  The volume control
would now be kept at maximum and would function more as a "gain" control - that is, to reduce the amount
of input to the radio's modern amplifiers since the new head preamp is now "hotter" than the original.

The balance control could be a "set and forget" control to allow for future wear on the head which can result
in output being unequal between left and right sides - but these added controls generally are not needed and may
only cause confusion to the operator.  Now, the signal flow is much easier to visualize and makes more sense as
the direction of signal flow remains the same regardless of which function the operator will be enjoying.

Barry's 8 Track Repair is the WORLD'S ONLY SHOP to offer this level of modification
to your Delco separate radio/8 track system !  The amount of additional cost for this
upgrade varies depending on the complexity of your current system, and we will need
to also modify your wiring harness which connects the 8 track player to your radio
in order for the customer to simply plug everything back in with no confusion.
Back to "Watch Us Convert Your Radio" page - hit browser "Back" button or  CLICK HERE
To "Conversion FAQ" page -  CLICK HERE
To start over with Conversion -  CLICK HERE
To E-mail with questions -  CLICK HERE
or E-mail us at  barry8track@cableone.net
Call  928-533-9666 (Paying Repair Jobs ONLY)
DO NOT CALL FOR BELTS, PARTS OR FREE REPAIR ADVICE!
.
To call with questions, dial 928-533-9666
Delco unit pictured sent in by customer Matthew Hayduk of Grosse Pointe, MI
SEE AND HEAR the brighter sound of a Delco 8 track unit I've converted -  CLICK HERE