Playback Gain; Erase Current; Overall Frequency Response - Technics RS-B11W Service Manual

Playback gain

@
(TAPE II] , TAPE [ll )
1. Test equipment connection is shown in fig. 2.
2. Playback standard recording level portion on test tape (QZZCFM 315 Hz) and,
output level at test points [TP4 (L-CH), TP5 (R-CH)].
3. Make measurements for both channels.
I
Standard value: 0.42V [0.4V: at LINE OUT jack]
Adjustment
1. If the measured value is not within the standard, adjust TAPE
( L-CH) or VR4 (R-CH) (See fig. 1).
2.
After adjustment, check "Playback frequency response" again.

Erase current

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(TAPE [ll)
1. Test equipment connection is shown in fig. 9.
2. Place UNIT into metal tape mode.
3. Press the record and pause buttons.
4. Read voltage on VTVM and calculate erase
formula:
( A) =
Erase current
I
Standard value: 160 �
5. If the measured value is not within the standard value adjust it by
following the adjustment instructions.
Adjustment
1. Short-circuit the registers R143, R144, R145.
(Refer to table 1)
2. Measure the erasing current.
3. If the measured value is not within the standard value,
or
open short-circuit
according to table 1.
Ci
Overall frequency
response
(TAPE �)
Condition:
• Playback mode
• Normal tape mode
Condition:
• Record mode
• Metal tape mode
current
Voltage across resistor R152
1 (Q )
I
�g
mA (Metal)
the registers R143, R144,
Condition:
• Record/playback mode
• Normal tape mode
2
• CrO tape mode
• Metal tape mode
• Input level controls ... MAX
- 7 -
Equipment:
• VTVM
• Oscilloscope
• Test tape ... QZZCFM
I
II] VR1 ( L-CH) or VR2 (R-CH), Tape
Equipment:
• VTVM
• Oscilloscope
by following
Record mode
R152 (1Q) -
R143 R145 R144
R145
Short Short Short
Short Short Open
Short
Open Short
Open Open Open
Equipment:
• VTVM • Test tape
• ATT
• AF oscillator
• Oscilloscope
• Resistor (600Q)
using VTVM, measure the
[ll VR3
Erase head
:<fi
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TP3
t:B
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o ; °
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-IO
,... IO
VTVM
Oscilloscope
'1'17"
Fig. 9
Change
Illustrations
in value R143 R145 R144
jb ' ·
Soldered
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±OmA
,, : 1
R143 R145 R144
Soldered�
+4mA
R R
f l�: dered
+10mA
R143 R145 R144
l
9 9
9
+20mA
Table. 1
(reference blank tape)
... QZZCRA for Normal
2
... QZZCRX for CrO
... QZZCRZ for Metal
X
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