Mechanical Adjustment; Electrical Adjustment - Sharp QT-12HS Service Manual

NT-12HS/HR/HB/HY/BL
NT-12ES/ER/EB/EY
PINCH ROLLER PRESSURE CHECK
1) Place the unit in play mode.
2) Push the pinch roller, at the point (A) shown in Figure 8—1,
by using a tension gauge (500 gr.) so that it will come off
the capstan. Then, slowly release the terision until the pinch
roller hits the capstan again (i.e., the pinch roller is about
to rotate again). Check, then, the tension gauge is reading
270 gr. to 330gr.
3) If the reading is outside the range of 270 gr. to 330 gr.,
bend the pinch roller spring or replace.
TORQUE CHECK AT PLAY, FAST FORWARD AND
REWIND MODES
Put a torque meter cassette in the cassette compartment
of the unit, and see that the measured torque in each
mode is normal as Table 8—1.
RECORD/PLAYBACK HEAD AZIMUTH ADJUSTMENT
1) Connect instruments as shown in Figure 8—2.
2) Set the mode selector switch at '"TAPE"' position.
3) Put a test tape (TEAC, MTT-114, 10 kHz 250 pWb/mm,
—10dB prerecorded) into the unit and play it.
4) Adjust the head azimuth adjusting screw so that the
electronic voltmeter reading is maximal.
Note:
If a dual-trace oscilloscope is available, perform the adjust-
ment so that the reading of the oscilloscope is maximal and
with the least phase/output difference between channels.
After the work, check that the head azimuth adjusting screw
has been secured completely.
TAPE SPEED ADJUSTMENT
1) Connect instruments as shown in Figure 8—3.
2) Play a test tape (TEAC, MTT-111, 3 kHz prerecorded).
3) Adjust the semi-variable resistor in the motor so that the
frequency is 2965 ~ 3015Hz on frequency counter.
Fast forward
MECHANICAL ADJUSTMENT
TENSION GAUGE
(500 gr)
CAPSTAN
PINCH ROLLER
TW-2231
85 ~ 130 g-cm
TW-2231 | 85 ~ 130g-cm
TEST TAPE
MTT-114
TEST TAPE
MTT-111
Table 8—1
DUAL-TRACE
OSCILLOSCOPE
HEADPHONES
PLAYBACK ich
mode.
ELECTRONIC
VOLTMETER
HEADPHONES
R-ch
Figure 8—2
REC/PB
HEAD
REC/PB
HEAD
HEADPHONES FREQUENCY Screwdriver
PLAYBACK mode COUNTER for high-fre-
quency use.
Motor
Figure 8—3
ELECTRICAL ADJUSTMENT
RECORD mode
BIAS OSCILLATOR FREQUENCY CHECK
1) Connect instruments as shown in Figure 8—4.
2) Set the function selector switch at ''TAPE"', and the beat
cancel switch at "A" position.
3) Place the unit in record mode, and see that the frequency
counter is reading 60 + 3 kHz.
Change the beat cancel switch from ''A" position to "B"
Position, "B" position to "C" position. Then see that the
frequency counter's reading is changed as shown in Table
8-2.
PLAYBACK AMPLIFIER SENSITIVITY CHECK
1) Connect instruments as shown in Figure 8—5.
2) Set the function selector switch at '""TAPE", the volume
control knob at "MAX", and the tone control knob at
"HIGH" position.
3) Playback a test tape (TEAC, MTT-118, 1 kHz, 250 pWb/
m, —10dB prerecorded).
4) See that the electronic voltmeter is reading about 1.2V.
OSCILLOSCOPE
ERASE HEAD
ELECTRONIC FREQUENCY
VOLTMETER COUNTER
Figure 8—4
Frequency
counter's
reading
Table 8—2
OSCILLO-
ELECTRONIC SCOPE
VOLTMETER
HEADPHONES
PLAYBACK mode
REC/PB
HEAD
Figure 8—5