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ITEM
MEASUREMENT & ADJUSTMENT
Playback gain
Condition:
* Playback mode
Equipment:
* VTVM
* Oscilloscope
* Test tape --- QZZCFM
Bias current
Condition:
* Record mode
* When bias current is
adjusted on one-channel
only, note that bias current
on the other channel may
vary.
* When L5 or L6 is the
replaced, preset core
position to bottom side of
coill and then readjust
optimum bias current.
Equipment:
*VTVM _ * Oscilloscope
Erase current
Condition:
* Record mode
Equipment :
* VTVM
* Oscilloscope
* Resistor (1)
5. Take measurement at middle section of tape.
Standard value: +1.5%
Adjustment method
1. Playback the test tape (middle).
2. Adjust so that frequency becomes 3,000 Hz.
3. Tape speed adjustment VR shown in fig. 21.
Tape speed fluctuation
Make measurements in same manner as above (beginning, middle and end of tape), and determine the
difference between maximum and minimum yalues and calculate as follows:
fi—f2
x
9
3,000
100 (%)
f1=maximum value, f2z=minimum value
Tape speed fluctuation=
Standard value: 1%
1. Test equipment connection is shown in fig. 8.
2. Playback standard recording level portion on test tape (QZZCFM 315Hz), and using VTVM measure
the output level at LINE OUT jack.
3. Make measurement for both channels.
Standard value: 0.39V
Adjustment
1. If measured value is not standard, adjust VR3 (CH), VR4 (R-CH) (See fig. 21 on page 5).
2. After adjustment, check "Playback frequency response" again.
. Test equipment connection is shown in fig. 11.
. Place UNIT into record mode, and tape selector to normal
position.
. Read voltage on VTVM and calculate bias current by following
formula:
R/P head
Value read on VTVM (V)
ig. 11
Bias current (A) =
10 ©)
Standard value: 285A (Normal position), 340A (Fe-Cr position),
380xA (CrO2 position)
. Adjust L5 (L-CH) and L6 (R-CH) (See fig. 21 on page 5).
Erase head
. Connect 1Q resistor between the ground side terminal of
erase head ground lead wire removed (See fig. 13).
. Connect VTVM to both ends of 12 resistor.
. Place UNIT into record mode, and measure voltage across the
12 resistor.
VTVM
Oseitoscope
. Determine erase current with the following formula:
Fig. 12
Voltage across both ends of 12 resistor
Erase head
1 (Q)
Record mode
Erase current (A) =
a)
Fig. 13
Standard value: More than 40mA (Normal position), More than 45mA
(Fe-Cr position), More than 55mA (CrOz2 position)
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