Technics RS-615US-D - Page 14

Bias current
Equipment:
* VTVM
* Oscilloscope
Erase current
Equipment :
* VTVM
* Oscilloscope
* Resistor (0.1)
MEASUREMENT & ADJUSTMENT
1. Test equipment connection is shown below.
TP1(L-CH)
2 (R-CH)
Record mode ra
R5(L-CH)
VIVM Oscilloscope
Fig. 24
2. Place UNIT into record mode, and tape selector to “NORMAL”.
3. Read voltage on VTVM and calculate bias current by following for-
mula:
Value read on VTVM (V)
10 (Q)
Bias current (A) =
Standard value:
+250uA
500 _ TS 0A (Normal, EX)
+250uA
600 15 0uA
|
\
|
|
Adjust L5 (L-CH) and L6 (R-CH) (See adjustment part location on
page 14).
. Then changing the tape selector to “CrOz”, confirm that bias current
become greater by 25% than that for normal.
. Connect 0.12 resistor between ground side terminal of erase head
ground lead wire removed (See fig. 26).
. Connect VTVM to both ends of 0.12 resistor.
Erase head
VTVM Oscilloscope
Fig. 25
. Place UNIT into record made, and measure voltage across the 0.12
resistor.
. Determine erase current with the following formula:
Voltage across both ends of 0.12
Erase current (A) = 0.10
Standard value: |
190 +35mA (Normal, EX) |
100 +40 mA (Cr02)
REMARKS
* Record mode
* Be sure the ground end of
the meter is connected to
the ground end of the
resistor,
* When bias current is the
adjusted on one channel
only, note that bias current
on the other channel may
vary.
+ When L5 or L6 ts the
replaced, preset core
position to bottom side of
coil and then readjust
optimum bias current.
* Record mode
Erase head
BLACK
Fig. 26
13
Overall gain
Equipment:
* AF oscillator
*VTVM
* ATT
* Oscilloscope
* Test tape
(reference blank tape}
---C-RA for Normal
-++C-RF for CrO2
. Test equipment connection is shown in fig. 27.
AF oscillator Record mode
LINE IN Test tape
* Record/playback mode
* LINE IN level control
-+»MAX
* Standard input level:
MIC +--+ —70£3dB
LINE IN —24+3dB
—3643dB