Zenith J584W - Page 11

FM AGC VOLTAGE CURVE
CHASSIS 1WJR55, 3WJR50, 50Z,
3WJR52, 52Z AND 15WJR29
In past years we provided a table of typical AGC vs. FM
input signal voltages measured at a given point in the FM AGC
circuit. These voltages would correspond to a given signal
level at the FM RF input. Those tables could be provided
because of the limited number of transistors in the circuit.
Integrated circuits have a large number of transistors included
within the chip (compared with a transistor only circuit),
and even though all transistors on a given chip can be held to
a very tight tolerance among themselves, the tolerances create
a unique condition. Voltage developed at the AGC terminal
of the IF IC (pin 7 of 221-89 and pin 15 of 221-108) varies
depending on the IF voltage sampled in the chip. If a fixed
input signal level were applied to several samples of a given
chassis model, the measured AGC voltage for that input level
will vary among the samples. Voltage measured under these
conditions is not a complete indicator of proper AGC action.
As an alternate to the voltage charts, we are now showing a
typical AGC Voltage Curve. Two important points must be
observed:
1. General shape of the voltage curve (when the voltages are
ploted for a curve).
2. AGC voltage will start to drop as the RF input level in 
creases to approximately 1000 microvolts.
9
TYPICAL IC AGC VOLTAGES
Chassis 1WJR55
Chassis 3WJR50, 50Z,
3WJR52, 52Z
Micro
Volts
Input
AGC Voltage
at Test Point "G"
Micro
Volts
Input
AGC Voltage
at Test Point "G"
0
4.70
o
4.78
25
4.65
25
4.70
100
4.65
100
4.65
200
4.58
200
4.58
500
4.50
500 4.50
1K
*4.50
1K
*4.30
5K
3.60
5K 2.72
50K
2.70
50K
1.45
100K
2.45
100K
1.11
Chassis
Number of
Channels
Watts Per
Channel
Power
Bandwidth
Total Harmonic
Distortion (THD)
No More Than
3WJR50, 50Z
2
2.5
100Hz - 10kHz
1.0%
8WJR56
2
7.0
60Hz-15kHz
1.0%
8WJR57
2
7.0
60Hz - 15kHz
1.0%
15WJR29
2
15.0
40Hz - 18kHz
0.5%
MINIMUM RATED POWER OUTPUT PER CHANNEL INTO 8 OHMS
(SINE WAVE CONTINUOUS AVERAGE POWER - OFTEN CALLED RMS POWER)