Teac A-450 - RECORDING PERFORMANCE; BIAS TRAP ADJUSTMENTS; RECORD BIAS SETTING

7-3. RECORDING PERFORMANCE
IMPORTANT
Before making any adjustments of the amplifier, be sure
that all tests in the playback performance section have been
accomplished and that all adjustments are correct. The
playback performance should be properly adjusted.
7-3-1. BIAS TRAP ADJUSTMENTS
NOTE
The VTVM used in this procedure must have load
impedance of 1 MQ or more.
1. Load any recordable tape.
2. Place the deck in the RECORD-PAUSE mode with no
signal applied.
3. Adjust L102/202 for a minimum reading.
7-3-2. RECORD BIAS SETTING
CrO, TAPE
1. Load a TEAC MTT-5OSTB test tape.
2. Adjust VC-101/201 to minimum (counter clockwise)
position.
3. Apply and record a | kHz signal at -15 dB (137 mV).
4. Rewind and play this recorded section and note the
VTVM indication.
5. Turn VC101/201 clockwise slightly and record another
section of tape.
6. Rewind over this section and play the tape again and
note the VIVM indication.
7. Repeat this operation of recording, rewinding, playing,
and adjusting until the peak value on the VTVM is
obtained.
8. Then, adjust VC101/201 slightly further clockwise
until the level decreases by 0.5 dB from the peak level.
9. After the above adjustment is done, apply and record
two tone signals in turn; a 1 kHz signal and a 10 kHz
signal, both at -38 dB (9.75 mV).
10. Adjust VC101/201 slightly until identical values at
both frequencies are found using the same process as
explained above.
NOTE
After adjusting the bias setting, the output level of
the 1 kHz signal must stay finally within the limits
(1.5 dB over-bias from the peak) as indicated in the
Fig. 7-12.
Fe-Cr TAPE
11. This adjustment is the same as using the method?
described in the “CrO. Tape” with the exceptions of 3
following items.
BIAS/EQ switches: “2” position
Test tape: MTT-504T
Adjustments: VC102/202
22
T RESPONSE 9 ——>
CONNECTION
VTVM
Ciz2/Ce2z
Qws/Q208
Fig. 7-11 Connection
SWITCH & CONTROL SETTING:
“-- DOLBY
CNR FM/coPy J source
e—n ~ pM
: . @
_ OUTPUT Control: Specified Control Setting (See 7-1-2)
. LINE Control:
MIC Control:
Specified Control Setting (See 7-2-2) |
Minimum Setting i
CONNECTION: See Fig. 7-10
: SWITCH & CONTROL SETTING:
all the same as above section.
Coarse adj. at IkHz/-15dB
(O.5dB decrease from peak output level.)
Fine adj. at [kHz & lOkH: /~38dB
{output levels of IkHx & IOkHz signals are the ;ame.)
Fine adj. must be within 15dB over-bias po tion
of IkHx signal from peak .
BIAS CURRENT ——»
Fig. 7-12 Bias Adjustments (CrO2 & FeCr tapes)