Bias/Erase Oscillator Check; Audio Record Bias Setting - Sony AV-3600 Service Manual

audio
oscillator
attenuator
AV-3600
1
kHz,
-65
dB
MIC
IN
LINE
OUT
jack
jack
m
100
ka
777
mr
VTVM
A.
OdB
(0.775V)
Fig. 7-3.
Record
level
calibation set-up
7-4.
BIAS/ERASE
OSCILLATOR CHECK
7-5.
AUDIO
RECORD
BIAS SETTING
Test Point-
Check:
Adjustment:
Signal
Source-
Equipment
Required:
TP-503
(Erase
Osc Output)
270
V
(p-p)
None
None
required
Oscilloscope
Procedure:
1.
Set
up
the
Record mode.
2.
Connect the scope
to
TP-503.
The
scope should indicate
more than 270
V
(p-p).
Also,
make
sure that the
frequency
is
between
80
kHz
and 100
kHz
(12.5
jus
and
10
/is).
If
the scope
waveform
does not
conform
to rated
specifications,
check and troubleshoot
the
erase
oscillator circuit.
Test Point-
Adjust
for:
Adjustment-
Signal Source-
Equipment
Required:
Procedure:
TP-504 (Audio Head
Input/Output)
22
volts.
C532
(Bias),
L401
(Dummy
Coil)
None
required
(1)
AC
VTVM
(2)
Blank tape
1.
Thread
the tape
and
set
up
the Record
mode
with no
input
signal.
2.
Connect the ac
VTVM
to
TP-504.
3.
Adjust
C532
(Bias) to
produce
a
22
volt
rms
reading on
the
VTVM.
4.
Play
back
the tape.
5.
Set
up
the
Audio
Dub
mode.
6.
Adjust L401
(at
the top center
on
ttie
SV
Board)
for
the
same
reading
as that in Step
3.
7-3