Panasonic RS-736US Service Manual page 13

BIAS OSCILLATOR CURRENT & BIAS TRAP ADJUSTMENT
Instruments required: VTVM, 10Q resistor
1. Remove the lead wire (which is on ground when
ADJUST
recording) connected to the recording head,
and attach a 10Q, resistor in series.
Voltage value C121, oR
ADJUST
TRIO 2SC644(RS) TRI2 2SC828(RS)
BIAS LEAKAGE CHECK
Fig. 23
Adjustment method:
1. Place the unit in the stereo recording mode and adjust the peaking coils, L5 and L6, to minimize bias leakage.
(Check points: collector terminals of Tr12 and Tr25)
2. Adjust VR31 and VR32 until the bias current shows the standard value.
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ERASE CURRENT
Instruments required: VTVM, 10Q resistor.
1. Remove the ground lead wire connected to the
erase head, and attach a 10Q. resistor in series.
2. Connect a VTVM to both ends of the 10Q. re-
sistor, and measure the voltage value. |
Voltage value
Resistance value (10Q)
3. The standard erasing current is 55~75 mA.
Erase current =
Fig. 24
12