Denon DN-780R Service Manual page 10

5. Checking the Take-up Torque
Load the cassette type torque meter
FWD side ......... SONY TW2111A
REV side .......... SONY TW2121A
Check to make sure that the average torque meter reading
is within 30 ~ 70g-cm during playback. If it is not within
this range, check the voltage (approx. 4V) of the reel motor.
After the verification, replace the reel motor if there is no
problem with the voltage value.
6. Checking the FF and REW Torques
Load the cassette type torque meter (SONY TW2231).
Check to make sure the torque meter indicates within
90 ~ 180g-cm at the end of FF and REW.
7. Checking the Back Tension Torque During
Record/Playback
Load the cassette type torque meter
FWD side ......... SONY TW2111A
REV side .......... SONY TW2121A
Check to make sure the torque meter reads between
2 ~ 6g-cm during playback and that there is no unevenness.
8. Checking the FF and REW Times
Load a C-60 cassette tape (TDK AC-514); check to make
sure the tape is fast forwarded or rewound within 85 ~
115 seconds. If it is not within this range, check sections 5
and 7.
9. Checking the Operation of the Erase
Prevention, Metal and Chrome Switch
Confirm that the sensor arm properly detecting the tape
type detection holes on the cassette housing.
ADJUSTING THE ELECTRICAL SECTIONS
Measuring instruments necessary for
adjustments
(1) Audio signal generator
(2) Variable resistance attenuator
(3) Electronic voltmeter
(4) Oscilloscope
(5) Frequency counter
(6) Adjustment screwdriver.
(7) Trap coil adjustment square stick
(8) Test tapes (SONY TY-224)
(A-BEX TCC-130, TCC-153, TCC-262B/162B)
(TDK AC-514)
(9) Transport Check cassette tape (A-BEX TCC-902)
Caution on adjusting
(1) Before adjusting, clean the head surface, capstan and
the pinch roller with a gauze or cotton swab moistened
with alcohol.
(2) Demagnetize the R/P HEAD and the E HEAD with a
head eraser.
(3) Completely demagnetize the adjustment screwdriver.
(4) Unless instructed otherwise, set the various controls
as follows:
INPUT volume ....................... maximum
DOLBY NR button ................. OFF
TAPE SPEED-A (-B) ............. Center click position
PHONES SELECT ................ MIX
INPUT SELECT .................... LINE B
1. Tape Transport Check
Load the transport check cassette. In the operational mode,
illuminate the fixing guides of the R/P HEAD with a lamp
and check to make sure the tape edge does not come in
contact with the tape guide section.
The tape transport is the most important element in
determining the performance of a cassette deck.
Avoid moving the various adjustment screws, nuts, etc.,
as much as possible. Refer to the pages on "Adjusting
and Cheking the Mechanism Section" when replacing or
adjusting the R/P HEAD.
2. Adjusting the Azimuth
(1) After completing the tape transport check, load the
test tape (A-BEX TCC-153).
(2) Playback (both FWD side and REV side) the test tape;
adjust the azimuth screw so that section A of the
Lissajous waveform is maximum and section B is
minimum.
PB Amp
LINE OUT
L
R
A-BEX TCC-153
R/P Head
FWD
DN-780R
V
H
REV
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