Pontiac FIREBIRD 1972 Service Manual page 1429

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1972 PONTIAC SERVICE MANUAL
select a high fidelity tone on either AM or FM stations.
AM and FM operation on A, G and F Series is controlled
by extreme lefthand (AM) and righthand (FM) buttons.
The left radio knob turns the radio ON and OFF and
controls the volume. The tone control bezel (behind the
left knob) is turned counterclockwise for bass tones and
clockwise for treble tones. When indexed at the detent, it
provides a balanced normal tone.
The right knob is used to tune stations manually. The
bezel behind the knob is the front-rear speaker control (if
so equipped).
On B Series an AM-FM selector bar is located directly
above the dial face. Movement of the bar to the left ex-
poses the letters "FM" and switches the radio to FM
band. Movement of the bar to the right provides AM
band. An automatic frequency control circuit is incor-
porated in the radio and automatically keeps the receiver
on frequency. This eliminates any station detuning due to
temperature changes around the radio.
Due to the higher frequencies involved in the FM band,
reception is generally limited to an average of about 25
miles. Beyond this point station flutter or fading may
become apparent. FM reception is noise-free, provided
sufficient signal is present to allow the noise-limiting fea-
tures of the radio to operate.
ADJUST ANTENNA T R I M M E R
The proper adjustment of antenna trimmer is extremely
important to the operation of an auto radio.
NOTE: On A M-FMradios, aadjustment must be
made on AM band only. Tnrimmer adjustment
on FM band is internal to the radio and is
independent of the antenna being used.
1. Tune radio to a weak station near 1400 KHz which
can barely be heard with volume turned fully clock-
wise.
2.
Remove right-side control knobs.
3. On cars equipped with monaural radios that have a
rear speaker, there are three small holes (electrical
connection points) in the receiver. which are located
directly behind right knob. The rear speaker control
has three prongs which interconnect these points.
When the control is removed to gain access to the
trimmer screw behind it, two of the holes (the center
and an outside hole) must be interconnected by a
short piece ofjumper wire to channel the audio signal
to a speaker. It is generally desirable to trim the radio
while using the front speaker.
4. Adjust antenna trimmei screw until maximum
volume is achieved.
5. Reinstall both right knobs.
The antenna trimmer adjustment should be made after a
set has been removed from car and worked on by a radio
repair man. The reason for trimming antenna after service
work has been performed is that the radio repair man will
undoubtedly have adjusted trimmer to match his antenna
so it no longer matches the antenna in the car from which
it was removed. Trimming the antenna is especially im-
portant with the all-transistor radio as this will directly
affect sensitivity and selectivity. Complaints of station
mixing on all-transistor radios can be eliminated by this
adjustment.
SET R A D I O PUSHBUTTONS
1. Turn radio on.
2. Pull out pushbutton until it stops.
3. Manually tune to desired station.
4. Fully depress pushbutton.
To set the radio for AM or FM reception on B Series
radios move the selector bar to "AM" position and per-
form the four (4) steps above. Then move selector to
"FM" position and repeat. In this manner five separate
AM and FM stations (total of ten) can be selected.
If the AM-FM selector bar does not move from one band
to the other, fully depress each pushbutton one at a time
to make sure that the pushbutton slide mechanism is fully
engaged.
DO NOT ATTEMPT TO MOVE SELECTOR BAR WHILE A
PUSHBUTTON IS PULLED OUT.
NOTE: On pushbutton selection, if the program
sounds shrill or distorted, it is probabfy caused
by improper tuning and can be corrected by
adjosting the tuning knob slightly. Since the
low notes are more affected by tuning than the
high ones, it is prefeable to tune the receiver to
a point where the low notes are heard best and
high notes are clear but not shn'll. This point
may be most readily found by listening to the
backgroundnoise ofa station and tuning for the
lowest noise level of the station. Turning the
control knob back and forth until the station is
almost lost on either side will enable the opera-
tor to hear the difference in reception and select
the intermediate position giving the best results.
AM-FM STEREO RADIO
On all series the multiplex adapter is incorporated in the
radio receiver. AM and FM operation is identical to that
described under "AM, AM-FM Radio". The volume and
tone control varies the volume and tone respectively in
both channels simultaneously. AM, FM, or stereo recep-
tion through the speakers is governed by the fader control