Playback Preamplifier Adjustment - Sony AV-3600 Service Manual

5-4.
Playback Preamplifier
Adjustment
(Head
Resonance and Playback
Equalization)
Frequency
characteristics
of the
playback
am-
plifiers
are adjusted to equalize head-to-tape character-
istics
and
to
obtain the desired overall
frequency
response.
Test Point/
Board:
Adjust
for:
Adjustment/
Board:
Equipment
Required:
TP-201/V2 (PBrf
output)
Correct
frequency response
as
shown
in Fig. 5-5.
C20
1 ,
R20
1 /
V2 (Head Resonance,
ChA)
C202,
R202/V2(Head
Resonance,
Ch
B)
L204/V2 (PB
Equalization)
R21
1/V2 (PB Equalization)
(1)
Oscilloscope
(2)
SONY
Alignment Tape
Procedure:
1.
Playback
the
rf
sweep portion of the
SONY
alignment
tape.
2.
Connect
the scope
to
TP201/V2
Board.
Sync
the
scope externally
from TP-412/SV
Board.
Set the
scope time base to
5
msec/cm. Four
markers
in
the
playback
rf
signal indicate
the
1
MHz,
2
MHz,
3.58
MHz, and
4.5
MHz
points.
3.
Set
R201
(resonance
gain)
fully
clockwise.
Set
R202
(resonance gain) fully
clockwise.
Adjust
C201 (Ch A) and
C202
(Ch B) for
resonant
frequency of
5
MHz.
4.
Adjust
R201
for
Ch
A
(R202
for
Ch
B) so that
the
amplitude
at 5
M*!z
is
equal
to
that at
2
MHz.
See Fig. 5-5
(a>.
5.
Turn
R
:
211 (equalizing gaLx) fully
counter-
clockwise.
Set the
equalizing
frequency
to
3.58
MHz
by
turning
L204.
6.
Adjust
R211
and
R2Gi
for
Ch
A
(R202 for
Ch
B)
to
obtain a rf
envelope approximately
flat
from
2
kHz
up
to 5
MHz.
See
Fig. 5-5 (a).
7.
Set
R211
so trrt the ratio
B/A
is
12596
±10%
A
the
amplitude at
2
MHz
B
the
amplitude
at
3.58
MHz
See
Fig. 5-5
(b).
(a)
A
B
(b)
Fig. 5-5.
Playback
rf signal