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- Select the input signal in such a way that the
"
output voltage on BU4 MONITOR
point 3/5 is
1V:i0dB
- Adjust R96 (R196) in such a way that the voltage
on BU4 MONITOR
point 6 (7) is 1.4 mV + 0.5 dB
- Adjust R54 (R154) in such a way that the left
(right) indicator hand indicates 100 %.
- Recorder in position: "START"
- "REC" -
"STEREO"
- "19"'
- R40 (R140) should be so adjusted that the left
(right) indicator hand indicates 100 %.
"A".
Adjustment of the premagnetization current
For a correct adjustment of the premagnetization
current it is necessary to compromize between the
frequency characteristic and the distortion. The
premagnetization current is determined by measuring
the voltage on BU4 MONITOR
point 6/2 (7/2) in the
recording position. The orientation value is 4 mV
and should be adjusted with R22 (R122). The
frequency should be 100 kHz + 10 %
- Insert an unmodulated tape of good quality
- Note the frequency characteristic (see Measuring
of the frequency characteristic). Add extra vaiues
in the range over 6,300 Hz.
- The curve over 6,300 Hz should more or less
correspond with the characteristic b shown
in
Fig. 18, whilst the after-tape distortion should
be <3 % at 1 kHz (100 % modulation).
When the high frequencies are weakened too much
(Fig. 18c), the premagnetization current is too
high. Are the high frequencies too strong (Fig. 18a)
and/or is distortion audible, then the premagnetiza-
tion current is too low.
Remark:
When adjusting one channel, the other may also
be somewhat influenced.
Measuring the frequency characteristic
- Insert an unmodulated tape of good quality
- Press the REC key
- Recorder in position: "B" - "STEREO"
- Control LEVEL
R703/753 to maximum
Control BALANCE
R704/754 in middle position
=
"19"
$344A7
Fig. 18
- Feed a signal of 333 Hz to BUS LINE IN/OUT
point 3/2 (5/2). This signal should be so strong
that the output voltage on BU4 MONITOR
point 3/2 (5/2) is 1 V + 0 dB (The indicator
reading should be 100 %).
Reduce the output voltage to 0.1 V (= -20 dB) by
means of the control LEVEL
R703/753.
Recorder in position: "START"
- "REC"
- "A" -
"STEREO"
- "19".
Make a recording of the following frequencies and
read the output voltages: 35 Hz - 40 Hz - 60 Hz -
333 Hz - 1 kHz - 8.2 kHz - 22 kHz - 25 kHz
The frequency characteristic which
is now measured
|
against the 333 Hz level, should lie within the
|
curve drawn in Fig. 19.
|
Likewise, the frequency characteristic at 9.5 cm/sec |
can be measured. The highest frequencies should
|
now be 17 and 18 kHz (see Fig. 19). At 4.75 cm/sec |
the output voltage should be reduced to 0.05 V
|
(-26 dB). The frequency characteristic should be
!
within 7 dB in the range 35 Hz - 11 kHz.
Check
on corss-talk
a. Channels mutually
- Feed a signal of 6.3 kHz/100 mV to BU3
LINE IN/OUT point 3/2 (5/2)
- Insert an unmodulated
tape
- Recorder in position: "REC" - "START"
-
"STEREO"
- "19"
- Control LEVEL
R703/753 to maximum
- The cross-talk rejection measured on socket
MONITOR
point 5/2 (3/2) should be_> 20 dB
(= < 100 mV) in position''A" and "B".
b. Tracks mutually
- Feed a signal of 6.3 kHz/100 mV to BU3
LINE IN/OUT point 3/2
- Insert an unmodulated tape
- Recorder in position: "REC"
- "START"
-
"STEREO"
- "19"
- Control LEVEL
R703/753 to maximum
- Make a recording of abt. 30 sec
- Reverse the tape
- Recorder in position: "START" - "STEREO"
- The cross-talk rejection measured on BU4
MONITOR
point 3/2 (5/2) should be > 60 dB
(=< 1 mV)
if this value is not reached,
it is advisable to
check the tape transport and the height of the head.
=
*"419"
ful
fu2
&7Scm/sec 10 kHz | kHz
95 cmjsec
17 kHz | 18kHz
19
cmjsec. 22 kHz | HkHz
Fig. 19
858786
CS55248
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