Dual C 812 Serviceanleitung Seite 11

Electrical Alignment
Test Instruments and Test Cassettes required:
2 AF Millivoltmeters
1 AF Generator
1 Oscilloscope
1 Test Cassette, 400 Hz, —20 dB, 10 kHz, —20 dB
1 Blank Test Cassette (Fe Tape), e.g. BASF Super LH, C 60
1 Blank Test Cassette
(Cr Tape, e.g. BASF Chromdioxid, C 60
1 Test Cassette, 400 Hz, Dolby Reference Level 200 nWb/m
General
Tape head and all parts of the tape guide system which will get in contact
with the tape must be carefully demagnetized before alignment! Re-
alignment must be performed in the seouence of operations listed below.
Multiplex filters T 101 and T 101' have been factory-aligned and should
not be touched.
Playback
Head Azimuth Alignment
Remove protective cover from record/playback head, insert test cassette
and advance tape to the gap alignment part, 10 kHz, —20 dB Connect
AF millivoltmeter to RCA (Cinch) output jacks OUTPUT L & IR. If only
one AF millivoltmeter is available, connect L & R outputs in parallel.
Depress Fe and I> pushbuttons
Adjust tape head to maximum voltage reading by means of the alignement
screw at the left side of the tape head.Secure alignment scrw after
completion of of azimuth adjustment with LOCKTITE, PI L-0 BOND
or bonding lacquer.
CAUT ION: Secondary peaks may beencountered when outputsare con-
nected in parallel. Always align heacrazimuthon on center peak indication.
Level difference between channel 1 and 2 at 10 kHz: <3 dB
Playback Level Adjustment
Insert Dolby Test Cassette (400 Hz Dolby Referenze Level)
Depress Fe, Dolby NR and
pushbuttons
Adjust output levels to 580 mV ±0,25 dB as follows:
Track 1, OUTPUT L with VR 101, Track 2, OUTPUT R with VR 101'.
Output levels should be measured at the RCA (Cynch) output jacks.
Playback Frequency Response
Insert Test Cassette (400 Hz, —20 dB, 10 kHz, —20 dB)
Depress Fe and I> pushbuttons. Release Dolby NR pushbutton (OFF)
Both level adjustment sections of the test cassette should produce equal
output voltages at the OUTPUT L & R jacks. If a voltage increase is
encountered at 10 kHz, —20 dB in comparison to 400 Hz, —20 dB,
disconnect the jumpers between A and B, or A' and 13', respectively.
If the 10 kHz, —20 dB level is lower than the 400 Hz, —20 dB level,
reinstall jumpers between A and B, or A' and B', respectively. Output
voltage at the OUTPUT L & R jacks should be +4 dB to —3 dB at
10 kHz with reference to the 400 Hz'; —20 dB level (equals 0 dB)
VU Meter Alignment
Depress Fe, Record, Dolby NR and>pushbuttons.
Connect the Ar generator to the input, the AF millivoltmeter to
the output jacks. Set level controls VR 102 and VR 102' to their full
clockwise position.
Adjust the AF generator to produce a 400 Hz output signal and adjust
the Input level of the cassettedeck for an output voltage reading of
580 mV at the Land R OUTPUT jacks.
Adjust control VR 104 (VU meter, left channel) and VR 104' (VU meter,
right channel) to produce a recording level indication of 0 dB on both
meters.
Hum and Noise Voltage
Measurements should be made with amplifier shield in place, taking care
to prevent hum induction by the tape head.
Depress Fe, Pause and>pushbuttons
Hum and noise voltage at the RCA (Cinch) jacks OUTPUT L and R
should not exceed 3 mV, when measured with a 20 Hz filier (such as
Sennheiser Model FO 55, Curve 2, 20 Hz, —3 dB) and in RMS value
rectification mode of the test instrument.
RF Oscillator
Depress Met, Record andl>pushbuttons.
Connect a frequency counter between TP 2 and TP 1 (Ground). Then
adjust the slug of oscillator coil (Ti 301) for a counter reading of 105 kHz.
R F Suppressor
Connect AF millivoltmeter or oscilloscope to TP 5 (right channel) and
TP 6 lieft channel). Then adjust L 1C2' and L 102 for minimum RF voltage.
RF Bias
Insert test cassette with blank Cr tape.
Depress Cr, Record and' pushbuttons
For basic alignment connect an AF millivoltmeter between TP 2 (left
channel) or TP 3 (right channel) and TP 1 (Ground). T hen adjust
VR 105 or VR 105', respectively, for a millivoltmeter reading of 58 my_
The following voltages should be measured depending on the tape
Selector switch setting:
Fe approx.
Cr
FeCr approx.
Met approx.
34 mV
58 mV
44 mV
74 mV
For exact alignment proceed as follows:
Record 400 Hz and 10 kHz test signals with a VU meter reading of
—20 dB on the blank Cr cassette. Compare recording levels during
subsequent playback. In case of unequal levels, the RF biasmust be cor-
rected as follows:
Adjust
Track 1 (left channel) with VR 105
Track 2 (right channel) with VR 105'
To effect less treble boost or more treble attenuation insert a blank
test cassette with Fe tape (BASF Super LH, C 60)
Depress Fe, Record and>pushbuttons.
Record 400 Hz and 10 kHz test signals with a VU meter reading of
—20 dB and compare recording levels during the subsequent playback.
If a voltage increase is encountered at 10 kHz as compared to the 400 Hz
test signal, R 325 and R 326 must beshorted. In case of voltage decrease,
disconnect R 326.
Insert blank test cassette with FeCr tape (Sony Ferrichrome, C 80)
Depress FeCr, Record and pushbuttons.
Record 400 Hz and 10 kHz test signals with a VU meter reading of
—20 dB. Compare recording levels during subsequent playback. If a vol-
tage increase is encountered at 10 kHz as compared to the 400 Hz test
signal, R 329 and R 330 must be shorted. In case of voltage descrease,
disconnect R 330.
Recording Level Alignment
Insert blank test cassette with Fe tape Depress Cr, Record, Dolby NA,
MPX, Line and' pushbuttons.
With LINE/DIN input level controls VR 102 and VR 102' in full clock-
wise position (open circuited), record a 400 Hz test signal with 0 dB
VU meter indication. Check VU meter readings during subsequent play-
back. Adjust VR 103 (VU meter, left channel) and VR 103' (VU meter,
right channel) for a recording current which produces equal recording
and playback levels, which means that 580 mV must be measured at
the L & R OUTPUT jacks.
Insert blank test cassette with Fe tape.
Depress Fe, Record, Dolby NR, MPX, Line andl>pushbuttons.
Record a 400 Hz test signal with 0 dB VU meter indication and compare
playback level by reading the VU meter indication again.lf the playback
level is higher, short resistors R 53 and R 154. In case of lower playback
level, disconnect resistors R 153 or R 154. Insert blank cassette with
FeCr tape (Sony Ferrichrome)
Depress FeCr, Record, Dolby NR ,MPX, Lineand pushbuttons. Record
a 400 Hz test signal with 0 dB VU meter indication and compare play-
back level by reading the VU meter indication again. If the playback
level is lower, disconnect R 145 or R 146. In case of higher playback
level, short resistors R 145 and R 146. Insert blank cassette with Meta I
tape (e.g. Scotch Metafinel
Depress Met, Record, Dolby NR, MPX, Line and' pushbuttons.
Record a 400 Hz test signal with 0 dB VU meter indication and compare
playback level by reading the VU meter indication again. If the play-
back level is lower, disconnect R 149 or R 150. In case of higher play-
back level, short resistors R 149 and R 150.
Overall Frequency Response
Overall frequency response for all types of cassette tape must be within
the prescribed to lerance envelope in accordance with DIN 45 500, sheet
4. Recordings must be made with a level of —26 dB below 0 dB indica-
tion of the VU meter.
dB
+1
0
1
2
3
4
5
6
11111111111111M1111111111 11B11111111111111111111
1111111111111»1111111111MIZMIll
iiiiuu
11111131111111111111111111111111•11111111111111111111111
11111111111111111111111311111111111111111111111111
1111111111111111111111.11111111111011111111111113111
1111111111111111113111111111111111111111111111111
INIBIIIIIM2/1111111111 MI 1MZMI CUM
1111111MMIIIIIII1111111111111111111111M
11111111111111•111131111111111111111111111111111111
"f(Hz)20 40
250 1000 8300 20000
Bottom Limit Frequency = 40 Hz
Top Limit Frequency = 12,5 kHz
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