Dokorder 7700 - Page 20

2-7
BIAS
TRAP
(REC.Arp)
a. Specification
\t
Minimum.
b. Adjustment
Adjust the bias trap coils L-601
(L-ch)
and L-602
(R
ch).
c.
Reference
Refer
to
Fig.
6-1.
d. Test tape. special
tools
and instruments required
Blank tape and VTVM.
e.
Test
point
Connect
the VTVM across the test
points
TP-7
&
TP-6.
and
also
across
TP-8
&
TP-6 on
the
AMP PC
Board.
f
.
Mode
of switch
(1)
Record
SW-ON
(2)
P.B.
level controls-M lN, Record level controls-M
lN.
g.
Procedure
(1)
Aftertheaboveconnectioniscompleted,loadtheblanktapeonthedeckandpushtherecordbuttonand
play
button
simultaneously
to enter
the
record mode,
then
push
the
pause
button
to stop the tape
travel.
(2)
Adjust
the bias
trap
coils
L-601
and L-602 on the
REC
switch
PC
Board
(PCM-397),
so that the
bias
leakage
may
be
minimum by reading
on the VTVM.
\t,
2-8
BIAS
TRAP 2
(P.B.
Amp)
a. Specif
ication
Less than
-30
dB
b.
Adjustment
Adjust the
bias
trap
coils L-1O2 and
L-2O2.
c.
Reference
Refer to
Fig.
6
1
.
d. Test
tape,
special tools and
instruments
required
Blank
tape
and VTVM.
e. Test
point
Connect the VTVM to the
line output
jacks.
f
.
Mode of switch
(1)
Monitor
SW-TAPE,
Record SW-ON.
(21
P.B.level
controls
MAX, Record
level
controls-MlN.
g.
Procedure
('1
)
Aftertheaboveconnectioniscompleted,
loadtheblanktapeonthedeckandpushtherecordbuttonand
play
button simultaneously to
enter
the record
mode, then
push
the
pause
button
to stop the
tape travel.
(2)
AdjustthebiastrapcoilsL-102andL-202ontheAMPPCBoard(PCM-446),sothatthebiasleakagemay
be
less
than
-30
dB on the
VTVM.
(3)
Change
the
record switch
over to OFF
position
and check that the
bias leakage is
less
than
-30
dB.
2.9 BIAS
SETTING
&
RECORDING
LEVEL
a. Specification
+0.3
dB
(Over
bias)
0
dB
(Recording
level)
b. Adjustment
(1)
Adjust the bias trimmer
capacitors
C-604
(L-ch)
and C-606
(R-ch).
(2)
Adjust
the semi-fixed
resistors
VR 102
(L-ch)
and VR-202
(R-ch).
c. Reference
Refer to
Fig.
6-1
.
I
17