Denon DR-F7 - Electrical Section Adjustments

ADJUSTING THE ELECTRICAL SECTIONS
e Measuring instruments necessary for adjustments
(1) Audio signal generator
(2) Variable resistance attenuator
(3) Vacuum tube voltmeter
(4) Oscilloscope
(5) Frequency counter
(6) Adjustment screwdriver
(7) Trap coil adjustment square stick
(8) Test tapes (TEAC MTT-111, MTT-114, MTT-150,
MTT-316 or 116K)
(MAXELL XL-11) C-46 or C-60
(DENON DX 3, DXM)
(COLUMBIA LX-C60)
(9) Transport check cassette tape
(COLUMBIA C-120, modified)
* Cautions on adjusting
(1) Before adjusting, clean the head surface, capstan and
the pinch roller with a gauze or a cotton swab moisten-
ed 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... „sun. maximum clockwise
— OUTPUT LEVEL volume . . maximum clockwise
— DOLBY NRswitch....... OFF
— TAPE SELECT switch..... CrO,
— MONITOR switch........ TAPE
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 de-
terming 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
Checking the Mechanism Section” when replacing or adjust-
ing the R/P HEAD.
2. Adjusting the Azimuth
(1) After completing the tape transport check, load the
test tape (TEAC MTT-114).
Play back the test tape; adjust the azimuth screw so
that section A of the resurge wave form is maximum
and section B is minimum.
(2
3. Checking and Adjusting the Tape Speed
(1) (DR-F6/F7)
(2
(1
(2
=16=
)
1) Connect the frequency counter to the LINE OUT
terminal and load the test tape (TEAC MTT-111).
F Counter
PB Amp
LINE OUT
3000
3000 Hz
26Η:
MTT-
2) Play back the test tape; at the midpoint of the
tape, where the transport is stable, adjust VR 1
of KU-0426 (DD MOTOR UNIT) so that the fre-
quency counter reading is in the range of 3,000 Hz
+ 61.
(DR-F8)
1) Adjusting the lock position
Measure the T.P. of KU-0434 (QUARTZ LOCK
UNIT) with the oscilloscope and adjust VR 1 of
KU-0426 (DD MOTOR UNIT) so that the duty is
50% (906 Hz) _
At this time, LE 901 (red LED) of KU-0434 will
light up.
2) Connect the frequency counter to the LINE OUT
terminal and play back the test tape (TEAC
MTT-111). Check to make sure the frequency
counter reading is in the range of 3,000 Hz + 6 Hz.
Adjusting the Input Sensitivity
Set the MONITOR switch to SOURCE position, the
operational mode at STOP. Supply a 400 Hz signal
using audio signal generator to the LINE IN terminal
and set the input signal level (approx. —18 dB) so that
the output level at the test point TP 51 (L ch) on the
Dolby circuit board becomes —2.5 dB.
Adjust Vr 301 on the audio circuit board so that the
output level at the test point TP 61 (R ch) on the
Dolby circuit board becomes —2.5 dB. In the case of
DR-F6, adjust Vr 204.
DOLBY Amp
LINE IN