Philips N 7300 - Adjustments and Checks; General Adjustment Guidelines; Mechanical Adjustments; Speed and Erase Head Calibration

IV. ADJUSTMENTS AND CHECKS
1. General remarks
— The electrical measurements and adjustments refer to
the left channel. The connecting points and controls
for the right channel are given in brackets.
— Before each measurement or adjustment with running
tape, heads and tape quides should be demagnetized
and cleaned.
— Do not use magnetized screwdrivers.
— All voltages given have been measured with an
electronic voltmeter.
— The outputs measured should be terminated with a
resistor of 100 kf2.
— Adjusted cores should be sealed.
— Adjusted screws and nuts should be lock-painted.
— Test tapes used:
. BASF-C264Z - 3922 566 21640
Unmodulated tape.
. DIN test tape 9.5
For adjustment of head inclination and azimuth and
check of the frequency response during playback.
. To check the tape speed it is possible to use:
3150 Hz 4.75cm/s 3922 566 21370
3150 Hz 9.5 cm/s 3922 566 21380
3150Hz 19 cm/s 3922 566 21390
2. Tape guides (item numbers 224, 229, 241, 273)
— The 4 tape guides have been accurately adjusted by the
factory and they should never be replaced simulta-
neously, for in that case there will be no reference
nainte loft
— Insert a tape and setect PLAY mode.
— The height of the replaced tape guide should be such
that the tape passes the outer tape guides at the lower
side and the inner tape guides at the upper side.
3. Tape tension comparators
To the indication on brackets 521 and 532 applies: each
mark is 29.
Mechanical
The force required to keep the lever in position —8°
should be 0.9 N. This force can be adjusted by changing
the suspension points of spring 217, 289.
After adjustment, the force required to keep the lever
in position +4° should be 0.7 N.
Electrical
The “output” (point 3 panel 3 A and point 1 panei 3B)
should be loaded with 100 kQ2 + 5 %.
The voltage should be measured with a voltmeter
Riz 1MQ.
In position 0° the voltage at the “output” should be
7.5 V + 0.2 V. The voltage can be adjusted by shifting the
metal core (bracket 523, 538) after screw M2x4 has been
loosened.
After adjustment the voltage at the output should be
5.7 V 0.3 V in position +8°.
CS 74 683
4. Brake (Fig. 6)
— When the brake solenoid is energized clearance A
between brake shoe and reel disc should be < 0.8 mm.
The brake shoe should not interfere with the reel disc.
The clearance can be adjusted by turning wheel C.
~ For winding the brake torque should be between
80 mNm and 88 mNm.
Brake torque = force x arm.
The brake torque is adjustable by changing suspension
point B of spring F2.
5. Reel disc (Figs. 8 and 9)
Height adjustment
— insert a tape.
— Select REW mode for checking or adjusting the left-
hand reel disc and FF mode for checking and adjusting
the right-hand reel disc.
The tape should wind in the centre of the reel.
The height of the reel disc can be adjusted by turning
adjusting screw G {accessible via backcover).
— The axial play should be between 0.1 mm and
0.15 mm. This is adjustable with adjusting screw H
which is countersunk in adjusting screw G.
— The clearance between the mounting plate of the reel
disc and the cabinet should be equal at the three fixing
points.
The clearance is adjustabie with the lower fixing screw.
Replacement
— Attention to toothing of reel disc and gear. They are
not the same left and right. (Check that reel disc is
clean and lubricate with Alvania.)
— Remove yea A from mivior shaft by tousening two
bolts B.
— Insert reel disc shaft partially in bearing and check
shaft distance | of reel disc and motor. This distance
1 should be 33.8 mm + 0.1 mm and is adjustable by
loosening screws J and displacing reel disc bearing in
slotted holes K.
Measure this distance by means of caliper gauge and
recheck after tightening screws J.
— Fix gear A and adjust height C by means of screws B.
— Locate earth spring (item number 234) and quide it
through eyelet of solder tag L.
— Guide reel disc shaft through bearing and lock it with
clamping ring (3,2 mm).
— Completely tighten adjusting screw G (clockwise).
Press pulley E (for left-hand side together with counter
belt) against stop F and fix with screw D.
— Adjust height of reel disc and axial play as described
above.
6. Flywheel {Fig. 7)
Perpendicular adjustment of capstan
— Insert a DP tape.
— Select PLAY made.
Turn screw A until tape runs flat between capstan and
pressure roller.
— Clearance between bearing and oil-retaining ring should
be between 0.5 mm and 0.8 mm.
This clearance is adjustable by moving the oil-retaining
ring.
7. Pulling force on tape
Below applies:
““REW-lever” is, seen from the back, the right-hand tape
tension lever.
“FF-lever” is, seen from the back, the left-hand tape
tension lever.
— Insert an 18 cm tape (approx. in middle of tape).
— Select PLAY made.
Adjust with R471 the “REW-lever” to +49 + 19,
Then the “FF-lever” should be adjusted to —8° + 19
with R477.
— Select PAUSE mode.
Press down the brake bracket rod until the brake shoes
are released from the reel discs.
Adjust with R475 the ‘’FF-lever” to +4° + 19.
— Select FF mode.
Adjust after approx. 5s the “"FF-lever” to --8° + 1°
with R473.
— Select REW mode.
Check after approx. 5s that “REW-lever” is at —8° +
2°.
8. Speed adjustment
— Connect a wow and flutter meter to BU4/BU104 LINE
OUT.
— Insert a test tape having a frequency of 3150 Hz
recorded at 4.75 cm/s, 9.5 cm/s or 19 cm/s dependent
on the speed to be adjusted on the set and play it back.
Adjust for correct speed by means of one of the trim-
ming potentiometers (see table below).
— After the speed adjustment the wow and flutter is
allowed tO Ve as indicated in the tabie Veiow.
Speed Trimming Wow and flutter
potentiometer
4.75 R801 <=+0,2 %
9.5 R802 <+0,15%
19 R803 <=+t+0,1 %
9. Suppression of radiation from erase oscillator signal
— Set recorder in position: 19 - ST - TAPE CUEING -
REC - PLAY.
—~ “LINE-OUT” control at “MAX”, other controls at 0”’.
— No tape in recorder.
— Adjust for minimum voltage (<= 10 mV) on BU3
(BU103) by means of L1 (L101).
10. Playback head (Fig. 5)
— Height and inclination of heads supplied by Service
have already been adjusted in factory.
— Tape guides should have been adjusted to correct
height (see chapter ADJUSTMENTS AND CHECKS,
paragraph 2).
70.1. Head inclination
— The front of the head should be exactly parallel to the
tape or perpendicular to the mounting plate.
— Check:
Playback the 10 kHz azimuth adjustment section of
the DIN test tape. Brake the left-hand reel slightly by
hand and measure the output voltages of both channels.
Braking should not cause the output voltage of both
channels to increase by more than 2 dB. (Should this
be the case, the tape path must be checked.) If, as a
result of braking, only the output voltage of the left-
hand channel increases by more than 2 dB, the head
inclines backwards. If braking only causes the output
voltage of the right-hand channel to increase by more
than 2 dB, the head inclines forwards.
Head inclination is adjustable with screw A.
10.2. Azimuth
— Playback the azimuth adjustment section of the DIN
test tape.
— The TRACK selector should be in position ST. The
signal should be as large as possible for both channels
simultaneously. This is adjustable with screw C.
11. Adjustment of playback amplifier
— Set recorder in position: 9.5 - ST - TAPE CUEING -
PLAY.
— LINE-OUT control at maximum.
— Insert a DIN reference tape for 9.5 cm and playback
the reference level section.
— Adjust for an output voltage of 0.6 V + 0.5 dB on BU4
(BU104) by means of R41 (R141).
12. Playback frequency response
-— Set recorder in position: 19 -ST - TAPE CUEING -
PLAY.
— LINE-OUT control at maximum.
— Insert a 19 cm DIN reference tape and playback the
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— The frequencies 40 Hz and 12.5 kHz should be within
7 dB with respect to the reference frequency.
The frequencies between 250 Hz and 6300 Hz should
be within 5 dB with respect to the reference frequency.
13. Recording head (Fig. 5)
— Height and inclination of the heads supplied by Service
have already been adjusted in factory.
— Tape guides should have been adjusted to correct
height (see chapter ADJUSTMENTS AND CHECKS,
paragraph 2).
— Connect the recording head as playback head by inser-
ting the plug of the recording head in the socket of the
playback head on PC-board 1.
Plug 3 in connector 4.
Plug 4 in connector 3.
— If necessary, head inclination and azimuth should be
adjusted as described for playback head.
— Reinsert the plugs in the original connectors.
— Set recorder in position: 19 -ST - SOURCE - PLAY -
REC.
— Insert a reference tape (BASF C264Z).
— Apply a signal of 1 kHz to BU1 (BU101).
— Set the indicators to 0 dB with recording controls.
— Set recorder in position TAPE CUEING.
— The output signal should be maximum and the phase
difference should be < 10°.
This is adjustable with screw C.
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