shaping is accomplished by a bias network in the base
circuit of Q4B. The response time of the operational
amplifier is determined by C9 and R23.
waveform of 1-c.
CONTROL SETTINGS: Same as 1-a.
Waveform same as 1-c. GOOD: Proceed to step 2-b.
BAD: Check wiring and S2-5F of SCAN WIDTH switch.
After repairing the shaping network it should be
waveform shown below.
V. Recheck waveform Test Point E.
PRESET SCAN AMPLIFIER
The -5 volt to +5 volt ramp from the Scan Generator
(A6) is applied to the base of Q1. The ramp is
processed by Q1/Q2 and Q3 to provide a 0 to +12.9 volt
ramp to the marker generator and the SCAN WIDTH
switch. Offset adjust A4R7 is adjusted to calibrate the
marker with respect to the FREQUENCY control.
50 MH4 FREQ.
Waveform GOOD: Proceed to step
Waveform BAD: Check Q2/Q3/Q4 circuits. If trouble is
not located proceed to step
waveform shown below:
Voltage regulation for the shaping network, consisting of
resistors R32 through R66, is provided by Q1. Diodes
CR10 through CR21 are sequentially forward biased as
the ramp voltage at the base of Q4 in the shaping
amplifier increases. As each diode is forward biased it
places additional resistive networks in parallel to reduce
the total resistance of the network. When the first local
oscillator is being swept from 200 to 310 MHz the ramp
voltage is controlled by the shaping network to provide
the exponential voltage ramp output required to linearly
marked with an asterisk are factory selected values.
Waveform GOOD: Proceed to step 4-b.
Waveform BAD: Input signal not correct or shorted Q1.
3-1. Measure voltage at the emitter of Q1. Should be
Voltage GOOD: Proceed to 3-b.
Voltage BAD: Check Q1 circuit.
3-b. Check biasing network voltages in the following
Same as 4-a.
SERVICE SHEET 7
1 MHz Crystal Oscil., Freq. Divider, & APC