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@
Erase current
Condition:
¢ Record mode
¢ Metal tape mode
RS-B25
Equipment:
¢ EVM (Electronic Voltmeter)
¢ Oscilloscope
. Test equipment connection is shown in fig. 9.
. Place UNIT into metal tape mode.
. Press the record and pause buttons.
. Read
voltage
on
EVM
and
calculate
erase
current
by
formula:
Voltage across resistor R301
1 (2)
Standard value:
155+15mA (Metal) (155+ 15mV)
Erase current (A)=
following
5. If the measured
value is not within the standard value adjust it by
following the adjustment instructions.
Adjustment
* If the erase current is more than 170mA, cut the jumper wire
(See fig. 1).
@
Overall frequency
Condition:
Equi
response
¢ Record/playback mode
e EV
pment:
e Resistor (6002)
M
° Test tape
¢ Normal tape mode
(Electronic Voltmeter) (reference blank tape)
¢ CrO, tape mode
© ATT
...QZZCRA for Normal
° Metal tape mode
¢ AF oscillator
...QZZCRX for CrO,
¢ Input level controls...MAX
© Oscilloscope
...QZZCRZ for Metal
Note:
Before
measuring
and
adjusting,
the
overall
frequency
response make sure of the playback frequency response (For
the method of measurement, please refer to the playback fre-
quency response).
(Recording equalizer is fixed)
1. Make connections as shown in fig. 11.
. Place UNIT into normal tape mode and insert the normal
reference blank test tape (QZZCRA).
. Supply a 1kHz signal from the AF oscillator through ATT to
LINE IN.
. Adjust ATT so that input level is —20dB below standard
recording level (standard recording level = 0 VU).
. Adjust the AF oscillator frequency to 1kHz, 50Hz, 100Hz,
200Hz, 500Hz,
4kHz, 8kHz,
10kKHz and
12.5kHz signals,
and record these signals on the test tape.
. Playback the signals recorded in step 6, and check if the
frequency response curve is within the limits shown in the
overall frequency response chart for normal tapes (fig. 10).
(If the curve is within the charted specifications, proceed
to steps 7, 8 and 9.)
If the curve is not within the charted specifications, adjust
as follows;
shown in fig. 12.
B
mens
oe
10)
1) Increase bias current by ("T=
1)
turning VR301 (L-CH) and [ft
turning VR301 (L-CH) and
VR302
(R-CH).
42. 5kHz
(See fig. 1.)
mae] | Nite"
||
Repeat steps 5 and 6 for
8kHz 7kHz 8kHz
confirmation (Proceed to
:
steps 7, 8 and 9 if the
Fig. 12
curve
is now
within
the
charted specifications as shown fig. 10.)
If the curve still exceeds the specifications (fig.
10), increase
bias
current
further
and
repeat
steps 5 and 6.
Overall frequency response chart (Normal)
TT
maaan
eels
40B
Tt
: ime= sant :
Hop
es >
HT
5OHz
100Hz
200Hz
SOOHz
1tkHz
2kHz
4kHz
10kHz
Fig. 10
EVM
Oscilloscope
Pruniniaee
tense Notes
(RS-B25)
i
Nenilineca
For overall frequency
EVM
Oscilloscope
response
measurement
For bias voltage
.
Adjustment (A):
Adjustment (B):
measurement
Fig. 11
When the curve exceeds the
Tit
71
When the curve falls below
overall specified frequency
4+—-+—]
5 —|
the
overall
specified
fre-
response chart (fig. 10) as
H} —>-3
—
quency response chart (fig.
as shown in fig. 13.
Reduce
bias current
by
VR302 (R-CH).
Repeat steps 5 and 6 for
confirmation (Proceed to
An TkHZ BH
steps 7, 8 and 9 if the
:
curve
is now
within the
Fig. 13
charted specifications as
shown fig. 10.)
If the curve still falls below the charted specifica-
tions (fig. 10), reduce
bias current
further and
repeat steps 5 and 6.
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