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4-3.
RECORD PERFORMANCE
IMPORTANT
Before making any adjustments of the amplifier, be sure that all
tests in the playback performance section have been accom-
plished and that all adjustments are correct. The playback
performance should be properly adjusted.
NOTE
Place DOLBY
NR switch to the OUT position for this record
performance test unless otherwise noted.
4-3-1. Bias Trap Adjustments
The bias trap tank circuit keeps the bias signal from reaching the
record amplifier.
Adjust for minimum
reading on VTVM
VTVM
Load a TEAC MTT-505 test tape on the deck.
Place the deck in the PAUSE mode with no signal applied.
Connect
a VTVM
between the Test Point (at junction of
L103 and C142) and ground. ©
Adjust L103 for a minimum reading on the VTVM.
Connect the VTVM
between the Test Point (at junction of
L203 and C242) and ground.
Adjust L203 for a minimum reading on the VTVM.
4-3-2. Bias Adjustments for "1" Position (CrO2 Tape)
R/P HEAD
—-
' N\
Mh
TP,
kio3/L203
=
{
a|
Cia2 /C242
Q107/Q207
T~403
—~ PAUSE mode —
Fig. 37 Bias Trap Adjustment (and T.P.)
OSCILLOSCOPE
1. Load a TEAC MTT-505 test tape on the deck.
2. Connect a VTVM to the
OUTPUT jacks.
bacilkaren
3.
Connect an AF oscillator to the LINE IN jacks, through an
attenuator.
4. Place the BIAS/EQ switches to the ''1" positions.
i
aa.
5. Place the deck in the record mode.
DECK
6. Apply 2 tone signals, in turn; a 1 kHz tone at 42 dB (6.15
attenuator
MAY
under TEST
ine
——s
SE
mV) and a 10 KHz tone at ~42 dB (6.15 mV).
oe Oe,
i
2°
7.
Rewind and play this recorded section of the tape.
1390
8.
Compare the differences between the output level of the 1
Fig. 38 Bias Adjustment Setup
kHz signal and that of the 10 kHz signal on the VTVM.
9.
The output level of the 10 kHz signal must be 1 dB below the
"f
1 kHz signal level.
+4
ae
10.
Adjust VC304/V C302, if necessary, to achieve this.
us
ae
11.
Continue
the process
of the recording-rewinding-playing-
roe
adjusting until this difference of 1 dB is obtained.
(-30)
0
~ Sine
{ <3
\kKHr
Sed 7
o
t
aa
z4
es
4-3-3. Bias Adjustments for "2" Position (Regular Tape)
B 6
Ss.
te)
'
12.
This adjustment is the same as using the method described in
ze
~s S.
4-3-2 with the exceptions of following items.
&
SS
5
OPTIMUM
VALUE
Test tape:
MTT-501
o
BIAS/EQ switches:
"2" position
ie See
» aa
rll
Adjustments:
VC303/V C301
\
BIAS CURRENT ——>
Fig. 39 Bias Current vs. Output Response Chart.
NOTE:
For actual adjustment/test point locations, see page 21.
17
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