Basic Alignment Procedure - Icom IC-H6 Service Manual

7- 5 BASIC ALIGNMENT PROCEDURE
7-5-1 P.L.L. CIRCUIT
A. Lock Adjustment
1. Connect the measuring instrument and set the control knobs as follows:
•Connect an oscilloscope (15MHz band width) to R217.
•Connect voltmeter between R205 and ground.
•Set the channel select switch at a programmed channel (center frequency of the operating
frequency range is recommended).
2. Procedure
Power
Supply
(8.4Vl
Oscilloscope
RF
Wattmeter
'------+--o
R21 7
PLL
R205
Frequency
Counter
When the circuit is operating normally, adjust coil L203. The
P. L. L.
will lock.
•Adjust the coil of L203, and the voltage of R205 varies between 0
~
6V, and P.
L. L.
should lock.
•Adjust L203 for 3V after lock.
Next, in Receive adjust L216 for maximum voltage
(P-P
value) on the oscilloscope and then
during transmission adjust L215 to maximum. Set the channel select switch at a high edge
channel, and repeat adjustment of L215, L216 several times. After that, confirm the following
voltage of R205 (both transmission and receiving)about 2V at a low edge channel and 4V at a
high edge channel, and that the voltage of R217 (both transmission and receiving) is over 2Vp-p
(over operating range of the radio). If the P.L.L. won't lock, check these voltages: R+6V, T+6V,
6V constant, and the P.L.L. LO and reference frequency oscillator for oscillation.
8.
Reference Frequency Oscillator Check
1. Connect a frequency counter through a capacitor to Pin 1 of IC203.
2. Confirm frequency is: 5.120MHz ±250Hz.
C.
P.L.L. LO Frequency Adjustment
1. Connection of the measuring instruments and the setting of knob.
•When adjusting the receiving frequency, connect the frequency counter to R257 through a
capacitor. After power adjustment, loosely couple the set to a frequency counter with capa·
bility of more than 180MHz (with dummy load connected), so that the transmitting frequency
can be obtained.
Power
Supply
(8.4V)
_ _ _ .. Dummy
Load
0
R257
(PLL)
7-6
Frequency
Counter
(TX) (RX)