Marantz SD9000 - Recording Compensating Circuit; Bias Oscillator Circuit;Erase Oscillator Circuit

3.4 RECORDING COMPENSATING CIRCUIT
(Tape Speed: 3-3/4 ips)
The method of recording compensation is the same as that
used
in
our
existing
units
where
the
amount
of
feedback
in the recording amplifier (Q902) is varied.
RIBS REC/SERCH HEAD
iM
1H
$30I-3 C134 RIa9
5
7 RIs23 &
8304-7 C138 RIS3
[eon
127 R42
cl
$303-! Riga cize
RI3G
abe |
s303-3 RI4? ci32
Tn
$302-3 RI48 C133,
S304-S C135 RISO $303-5 CI36 RIS! 8302-5 Cis
$302-7 C140 RISS| >
os
$303°7 C139 RIS4
Vee
$301: Tape selector switch — Normal
$302: Tape selector switch — Special/CrO2
$303: Tape selector switch — FeCr
$304: Tape selector switch — Metal
$305: Tape speed switch
Tape Speed | Tape Selector ?
(IPS) Position POMmPEnsanen
|
NORMAL
|
Peaking
by
L102,
C133
and
R148.
|
‘ Peaking by L102, C132 and R147
1 SPECIAL/ Mid range compensation by C128
e103 d R143
2 1-7/8 all
Peaking by L102, C131 and R146
' FeCr Mid range compensation by C126,
} C127, R141 and R142
et Peaking by L102, C130 and R145
es METAL Mid range compensation by C125
and R140
NORMAL Peaking by L103, C140 and R155
only
Peaking by L103, C139 and R154
SPECIAL/ Mid range compensation by C136
CrO2
3-3/4 and R151
Peaking by L103, C138 and R153
FeCr Mid range compensation by C135
and R150
Peaking by L103, C137 and R152
METAL Mid range compensation by C134
and R149
3.5 BIAS OSCILLATOR CIRCUIT/ERASE OSCILLATOR
CIRCUIT
The SD9000 has a bias oscillator circuit. and an erase
oscillator circuit to provide optimum bias and erase cur-
rent for the use of metal tapes.
@ The bias oscilator circuit is driven by a regulated amp-
lifier power supply.
@ The erase oscillator circuit is driven by the motor
power supply.
The bias current for any particular type of tape is selectable
by the circuit shown below (selection of bias current ‘is
independent of tape speed):
1. Bias Oscillator Circuit
As shown bellow, by varying the 0304 base voltage,
the bias oscillator circuit operational voltage is altered.
In case of 4-3/4 i.p.s. (9.5 cm/sec), do not adjust by bias
current. Adjust the recording EQ circuit, instead. Inci-
dentally, R307 is the bias fine adjust control on the
front panel.
0434
1403
L401 sane R410
RI T401
. " Is am LP 0 001
FeCr BIAS
CURRENT ADJ.
METAL BIAS
CURRENT ADy.
© To HOO!
$302-10 $303-9
s301-9 $301: Tape selector switch — Normal
$302: Tape selector switch — Special/CrO2
S303: Tape selector switch — FeCr
S304: Tape selector switch — Metal
Normal
1-7/8 ips R411
(4.75cm/s)| R410
2. Erase Oscillator Circuit
The erase oscillator circuit consists of Q417 and T402.
Only in case of metal tapes, R321 is shorted to increase
the erase current.
ERASE HEAD
x
3 ‘
—O To J416
R321 | R330
$ rses
$304-I0
$304: Tape selector switch — Metal