Sharp 8C221 Service Manual page 9

Test Equipment Connections:
GENERAL . . . . . . . . . . . . . . . . Connect AC power plug through
isolation transformer to power supply.
BIAS SUPPLY . . . . . . . . . . . . Apply t8V volts bias to TP204.
OSCILLOSCOPE . . . . . . Connect to TP203 through "IF TEST
BLOCK" shown in Figure 3. Detector terminal B
is connected to TP201.
SWEEP GENERATOR . . . . . . . Connect IF/VF output in
series with "Out Put Pad" shown in Figure 5 to
STEP ADJUSTMENT
Detector stage
Adjust 3 1.375MHz
attenuation of PIF
Recheck adjustment of I206 (Bottom core) for response as shown in "A" Figure 7.
Remove the Sweep Generator lead from TP201 and reconnect it to test point on tuner.
Remove the IF Test Block terminal A from the TP203 and reconnect it to TP201 of IF Test Block terminal B.
4
Apply +8.0 volts ACC bias to TP204.
Set channel selector to channel 10.
Check 31.375MHz
Adjacent channel
5
trap & sound trap
transformers
Adjust mixer col-
6 lector coil in VHF
tuner
Adjust 1st PIF
7
transformer
8
Recheck adjustment of Tl on tuner and T201 for correct response as shown in "B" of Figure 7.
Remove the IF Test Block terminal B from the TP201 and reconnect it to TP203 of IF Test Block terminal A.
9
Apply +8.0 volts ACC bias to TP204.
Adjust for proper
Recheck adjustment T204, T205 and for correct response as shown in "C" Figure 7.
Reset RF AGC control (R206) for normal operation.
PICTURE IF TRANSFORMER & TRAP ALIGNMENT
Refer to Figure 7.
MARKER
GENERATOR GENERATOR
3 1.375MHz
Same as Step 1
Same as Step 1
3 1.375MHz
Same as Step 1
Same as Step 1 Same as Step 6
Same as Step 1 Same as Step
MARKER GENERATOR . . . . . . Couple loosely to Sweep
Generator Output Cable to provide markers.
Note: . . . . . . . Preset RF AGC control to mid-position. Set
Channel Selector to Channel 10.
Alignment Procedure . . . . . . . . . See "General Alignment In-
COMPONENT
Adjust as shown on response curve "A" of
Figure 7.
(bottom core)
Adjust T206 (Top core) alternately for
maximum attenuation of 31.375MHz as
(Top co=)
shown on response curve "A" of Figure 7.
Adjust for minimum dip at 31.375 MHz,
on
Adjust for maximum gain and the response
VHF Tuner
curve "B" in Figure 7.
Align T204 and T205 for maximum gain and
6
obtain the response as shown in "C" Figure
9
PROCEDURE