Marantz SD1000 - Electrical Adjustments (Continued); Recording Bias Current Adjustment; Recording Current Adjustment Procedure

6.6 RECORDING BIAS CURRENT ADJUSTMENT
SET UP
1. Power voltage:- 50 or 60 Hz AC voltage rated for
the unit to be used in a market country.
2. TAPE SELECTOR switch:- NORMAL.
3. Load:- Measuring instrument input impedance.
PROCEDURES
Set up the tape deck in the recording mode of opera-
tion. Connect the VTVM to J101, J103 (Lch) and
J201, J203 (Rech). Adjust the variable resistor R909
and R929 for 4.2 mV VTVM read.
NOTES: 1. Proceed both for the right and left chan-
nels in the same manner.
2. For the tape deck equipped with the
TAPE SELECTOR switch, make certain
that the VTVM reads approximately
5.7 mV with it set to the CrO, position.
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6.7 RECORDING CURRENT ADJUSTMENT
SET UP
1. Power voltage:- 50 or 60 Hz AC voltage rated for
the unit to be used in a market country.
. Input signal:- 1 kHz, 1 mV. (-60 dB)
. TAPE SELECTOR switch position:- NORMAL.
. Load:- Measuring instrument input impedance.
. Tape Speed:- 1-7/8 IPS (or 3-3/4 IPS).
PROCEDURES
1. Stop the recording bias current oscillation by dis-
connecting the bias circuit. For example, connect
the base and emitter of 0941 the base and emitter
of Q942. (Complete adjustment as quickly as
possible.)
. Set up the tape deck to the normal recording state.
Connect the VTVM across the 10 {2 resistor con-
nected to the head. Supply 1 kHz, 1 mV to the MIC
terminal. Adjust the RECORD LEVEL control until
the LED meter indicates OVU. Adjust the variable
resistors R138 (or R137*) and R238 (or R237*)
until the VTVM reads 0.5 mV, respectively.
. Operate the oscillation circuit. Record 1 kHz, 1 mV
signal. Play back the recorded signal and adjust
R138 (or R137*) and R238 (or R237") for OVU
LED meter reading.
NOTES: 1. Proceed both for the right and left chan-
nels in the same manner.
2. After adjustment, release the recording
bias current.
3. Resistors marked * are to be adjusted for
3-3/4 ips.
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