July 1957 Radio & TV News
of Contents] These articles are scanned and OCRed from old editions of the Radio & Television News magazine.
Here is a list of the Radio & Television News articles
I have already posted. All copyrights are hereby acknowledged.
was part of the hey day of the newfound radio-in-your-car craze, and
the public was voraciously consuming all the high tech equipment it
could afford. Rock and Roll music was on every teenager's mind and many
guys for the first time were able to have their own wheels and were
outfitting them with sound systems that could blast the latest works
of Buddy Holley, Chuck Berry, Elvis Presley, and Fats Domino. Those
machines were the first babe magnets used for cruising the strip on
Saturday nights. Radio stations were popping up all over the country,
enabling cross-country travel with non-stop music, news, and variety
show entertainment. Ford and Chevrolet were not going to miss an opportunity,
so they delved into the high end mobile radio manufacturing business.
As the quality of broadcasts increased, noise cause by automobile ignition
systems bubbled to the top of issues affecting listing pleasure, including
the distance over which a broadcast could be received. This article
describes Ford's efforts to please their customers' demands.
Here is the equivalent report for
1957 Auto Radios: Ford
Fig. 1. Ford speakers feature a dust shield with four self-cleaning
A systematic check can pinpoint many faults without chassis removal.
Dismantling itself is no problem.
If readers of our other presentations
on this year's car receivers have retained any doubts as to the established
position of transistors, low-voltage miniature tubes, and printed circuits
in this field, the three basic radios used in the 1957 Fords do nothing
to encourage such hesitation. All three models follow the noted trends.
Some innovation also appears in the speakers used. Continued
reliable performance from these components is assured by the use of
a sealed magnetic structure and incorporation of dirt-release holes.
The four release holes can be seen near the apex of the cone in Fig.
1. Vibration of the speaker in ordinary use propels foreign particles
out of these openings, but the valve-like action provided by the small
size of the openings impedes the return of dirt and dust.
of the receivers available for all Ford cars except the "Thunderbird"
is the 75MF. This push-button hybrid includes among its five tubes a
12BL6 r.f. amplifier, a 12AD6 converter, a 12AF6 i.f. amplifier, a 12AJ6
detector - 1st audio stage, and a 12K5 audio driver. A 2N176 audio output
transistor is mounted on a heat sink at one side of the chassis.
Another five-tube unit also using low-voltage tubes in a hybrid
design is the 75BF. It uses a 12AF6 as the r.f. amplifier, but otherwise
follows tube line-up of the 75MF up to the 1st i.f. stage. This is followed
by a 2nd i.f, amplifier (12CN5), which feeds a 12J8 detector-1st audio
tube. The usual audio driver for the transistor is here omitted, with
the 12J8 directly feeding the 2N176.
For those who like their
auto radios with plus features, Model 78MF provides search tuning and
push-pull transistor output, supported with eight low-voltage tubes.
Two 12AD6's are used as the r.f. amplifier and converter. The two-stage
i.f. strip employs a pair of 12AF6's; and the detector-1st audio portion
is handled by a 12AJ6. The conventional 12K5 audio driver feeds the
push-pull 2N176 pair of transistors. The trigger amplifier for the search
tuner, a 12AE6, feeds the 12K5 control tube, which operates the relay.
Fig. 2. Location of leads to receiver.
Fig. 3. The receiver and the dashboard.
Fig. 4. Details for installing or checking noise suppression
equipment. See text.
As with most auto radios, a defective receiver, once it has been determined
that the fault is in the circuit itself, can be handled on the service
bench with no more difficulty than is experienced with any other radio.
Two problems must be faced first, however. The first of these involves
prior determination of whether the symptom under examination is actually
traceable to the receiver. Then, if it is indeed found to be in the
circuit, the business of getting the chassis out of its secure position
behind the dash panel (and subsequently that of returning it in satisfactory
fashion) must be faced.
To attack the problem systematically,
a kit of parts for troubleshooting is recommended. These include spare
5- and 7.5-ampere fuses, one each of every tube type used in the receivers,
a spare speaker, a spare antenna with lead, and a set of suppression
equipment. All parts except fuses should be pre-tested and marked so
that they will not be left in the radio inadvertently during substitution
tests. Thus armed, the technician is ready to localize symptoms with
the receiver still mounted.
No reception: The fuse is checked
first. If it is blown, a new one is tried. If this also blows, the next
step is removal to the bench. If it does not blow, check to. see whether
the tubes are lit. If they are not, the availability of voltage at the
A lead (see Fig. 3) should be checked with a meter. If tubes are lit,
the substitute antenna should be tried to see whether the trouble can
be isolated to this section. Similarly, the substitute speaker can be
tried. To avoid damage to the transistor, never operate the radio without
If none of the measures noted localizes the trouble,
step-by-step substitution for each tube is the final test before removal
to the bench becomes mandatory. Check of the output transistor(s) should
not be attempted with the radio in the vehicle. This component is not
considered a likely source of trouble in any case.
erratic reception: To isolate, it is important to know when the noise
occurs. If it is present when the engine is not running, the defect
is probably in the receiver. However, all leads to and from the chassis
(Figs. 2 and 3) should be checked first for secure connections. If noise
is present only when the engine is running, and even when the vehicle
is not in motion, check the suppression equipment. More detailed reference
will be made to this equipment later in connection with Fig. 4. Also
make sure that the receiver is properly grounded both to its support
bracket and to the contact with the instrument panel. Noise that occurs
only when the auto is in motion may be due to intermittent contact to
automobile ground, through either the support bracket or the instrument
panel. However, also keep in mind the fact that, if there is intermittent
contact with the antenna or another part of the antenna system, similar
indications will result. These other possibilities should also be checked
when the noted symptoms are present.
Distorted or garbled sound:
Before dismantling the radio, it is a good idea to check the speaker
and individual tubes by substitution. Sometimes, if the speaker is improperly
mounted, bending or twisting may throw the voice coil out of alignment.
Mounting nuts should be tightened by hand only. If wrench or pliers
are used for this operation, there may be a tendency to over-tighten,
with poor sound resulting.
Some cases of weak reception can
also be corrected without chassis removal. The antenna trimmer, which
is accessible externally (Fig. 3), may be misaligned. It should be adjusted
with the antenna fully extended. When the search tuner tends to run
continuously without stopping on certain stations, it is well to remember,
the actual trouble may also be poor sensitivity. In this connection,
note that poor sensitivity and the other symptoms that may result from
it can be evident when the auto's battery voltage is low. A check of
battery voltage may often save the job of dismounting the radio for
a bench check.
Suppression equipment: When it becomes necessary
to check or install suppression equipment, make certain that all paint
and dirt are removed from between capacitors and the vehicle and that
all nuts and bolts are tight. The lead shown as Item A in Fig. 4 is
the high-voltage distributor-to-coil wire. The generator suppressor
capacitor is shown as Item B. To remove or install it, it is not necessary
to remove the bolt. The latter need only be loosened enough to slide
the mounting bracket under the lock washer. The capacitor for the voltage
regulator is shown at G, and the bonding clip is located as shown in
To get at the static collectors, the front hub grease
caps, as shown, must be removed. Make sure that the cotter key is bent
away from the spindle center hole so that it will not interfere with
the static collector. The bonding cable - this applies to 8-cylinder
models only - is shown in heavy outline in Item E.
considerations: When tube substitution is necessary, access is obtained
simply by removing the bottom cover of the receiver. This should present
no problem. The tubes may then be found, protruding downward from the
chassis plate and within convenient reach. When the receiver itself
has to be taken out, the most advantageous position to assume for this
chore is in the center of the front seat, directly in front of the receiver
dial. Be sure that the ignition switch is off. As a preliminary step,
the air-duct assembly on the right hand should be removed to get it
out of the way.
The three leads connecting to the radio - the
antenna lead, the A lead, and the pilot-light lead - should now be disconnected,
and the fuse withdrawn from its holder. Next remove the control knobs,
bezel-mounting nuts, bezel, and the panel-mounting nuts. The leads are
shown in Figs. 2 and 3. The hardware should present no problems.
The lockwasher on the stud at the right side of the chassis is then
removed, and the mounting bracket is pushed away from the stud. Now
the bolt from the other bracket, at the lower left of the chassis, is
Now the receiver is free of its mounting, but
must still be maneuvered out of the space in which it is located and
into the clear. To complete removal, grasp the chassis with both hands,
push it forward, and tilt it toward the toe-board until it clears the
instrument panel. This completes the job.
To get the receiver
back into position, the dismantling procedure is reversed with very
little change. The entire unit is guided into position with both hands
but, once it is oriented, it is steadied in place with one hand while
the other is used to install the panel-mounting nuts finger-tight only.
While it is thus held, slide the right-hand mounting bracket
over the stud at the right side of the chassis, and install the nut
and lock washer here. Be sure that all cables and wires are clear of
the chassis, else you may have to perform partial dismantling again
when you find that leads cannot be connected properly because they have
to become caught. Now you can install bolt and lock washer to the stud
on the left side. Getting the bezel and the hardware in place is a relatively
simple matter. Next the speaker plug, A lead, antenna lead, and fuse
are returned to place. Be sure that they are securely connected. Last,
don't commit the common oversight of forgetting to put the air-duct
in place. Posted
February 6, 2014