Playback Level Adjustment; Level Meter Adjustment; Bias Trap Adjustment; Erasure Current Adjustment - Pioneer CT-F850 Service Manual

9.2 PLAYBACK EQUALIZER ADJUSTMENT
1. Connect millivolmeters to the OUTPUT termi-
nals.
2. Set the tape selector to the TAPE position, and
turn the playback level adjustment controls
VR1o01 (Lch) and VR201 (Rch) up to maxi-
mum positions.
3. Play the 333Hz/—20dB section of the STD-
331A test tape.
4. Next play the 10kHz/—20dB section of the
same test tape, and adjust VRio1 and VR201
to obtain a +0.5dB level difference from the
333Hz signal used in step 3.
5. Also play the 14kHz section and check that
the level difference from the 333Hz signal
used in step 3 varies by no more than —2dB ~
+3dB.
6. Then switch the tape selector to the Fe-Cr,
CrOz and METAL positions, and play the
10kHz section at each tape selector position,
checking that the playback level lies within
—4.3dB + 1dB from the 10kHz playback level
adjusted in step 4 above.
9.3 PLAYBACK LEVEL ADJUSTMENT
Since this adjustment is used in determining
the Dolby NR level, it should be performed care-
fully and accurately.
1. Connect millivoltmeters to the No. 40 -(Lch)
and No. 39 (Rch) TP terminals in the mother
ass'y. ;
2. Play the 333Hz/OdB section of the STD-
341A test tape, and adjust VR102(Lch) and
VR202 (Rch) until the millivoltmeters read
1dBv (1.12V). =*3.2d8
38. Then turn the front panel OUTPUT levei
control around to the click-stop position (the
1 o'clock" position), and check that the OUT-
PUT level is —3dBv (710mV) when the 333Hz/
OdB section of the STD-341A test tape is play-
ed. Adjust with the VRio4 (Lch) and VR204
(Rch) controls if necessary .
9.4 LEVEL METER ADJUSTMENT
1. Connect the millivolmeters to the mother
ass'y TP terminals No. 42 (Lch) and No. 41
(Rech).
2. Turn the DOLBY NR switch on, and the
MONITOR switch to SOURCE.
3. Apply a 333Hz/—10dBv (316mV) signal to
the INPUT terminals, and adjust the front
panel INPUT level control to obtain a —23dBv
(70mV) reading in the millivoltmeters.
(Leave the VR701 (Lch) and VR702 (Rch)
' controls in the display amplifier ass'y in the
central positions).
4. Turn VRuios (mother ass'y) counterclockwise
until the left and right channel level meter
readings of —20dB disappear.
5. Again apply the 333Hz/—10dBv signal to the
INPUT terminals, and adjust the INPUT level
control to obtain millivoltmeter readings of
—3dBv (710mV).
6. Adjust VR701 (Lch) and VR702 (Rech) in the
display amplifier ass'y so that the level meters
read OdB. (Turn VR701 and VR702 clockwise,
and stop once the OdB position is reached).
7. Then vary the input signal as shown in the
following chart, and check that the corre-
responding level ranges are satisfied. If the
radings fail to lie within the specified ranges,
repeat steps 3 to 6 above.
Table 1
TP Terminal Output Level Meter Reading
333Hz— 23 * dB
-20dB
9.55 BIAS TRAP ADJUSTMENT
1. Connect an oscilloscope to the OUTPUT
terminals.
2. Set the MONITOR switch to the TAPE po-
sition, the tape selector to the METAL po-
sition, and the OUTPUT level control to the
click-stop position.
3. Play back an unrecorded portion of metal
tape, or load an empty cassette half, and proce-
ed in play mode without any input signal.
4. Check that the output level at the OUTPUT
terminals is less than —45dBv (5.5mV).
5. If the output level exceeds this limit, adjust
L101 (Lech) and L201 (Rch) to obtain the
waveform of minimum amplitude in the
oscilloscope.
9.6 ERASURE CURRENT ADJUSTMENT
1. Switch the tape selector to the METAL po-
sition, and turn the INPUT level control down
to minimum level. Connect a millivoltmeter
across terminals no. 66 and 64 (GND) in the
mother ass'y.
2. Proceed in the recording mode but in the
absence of an input signal (an unrecorded
tape may be used for this purpose).
38. Adjust VRo9o01 in the switching ass'y until
the millivoltmeter reads 160mV. (Since the
signal frequency involved in this measurement
is the high bias frequency, the measurement
must be performed with care).
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