Panasonic RS-612US-D - Advanced Adjustments and S;N Ratio

11
Overall frequency response
(As a standard for adjustment)
MEASUREMENT & ADJUSTMENT
Adjustment— Using bias current
1. When the frequency response between the middle and high frequency
range becomes higher than the standard value, increase the bias current
by turning L3 (L-CH) or L4 (R-CH) in direction of counter-clockwise
(G)
2. When it becomes lower, reduce the bias current by turning in direction
of clockwise ( |) ).
REMARKS
Adjustment
stick
Overall S/N ratio
Equipment :
* VTVM
* AF oscillator
+ ATT
* Oscilloscope
* Test tape
(reference blank tape)
-+-C-RA
. Test equipment connection is shown in fig. 15.
2. Supply 1kHz signal to LINE IN and adjust ATT so that output level
at LINE OUT indicates 0.42 V (—7 dB).
. Make recording.
. Make another recording without supplying signal (disconnect input plug
to LINE IN).
. Rewind to recorded part and playback.
. Measure output signal level and no signal level (noise), and determine
the ratio in decibels (dB).
. The value is difference between “Playback S/N and overall S/N”, but
for decibel calculation refer to “Playback S/N measurement” on page
7.
Standard Value: Greater than 42dB
(without NAB filter)
Dolby NR circuit
Equipment :
* VTVM
* AF oscillator
* ATT
* Oscilloscope
. Place UNIT into record mode, set the Dolby NR switch to OUT posi-
tion and supply to LINE IN to obtain —34.5dB at TP3 (L-CH), TP4
(R-CH) (frequency 5kHz).
. Confirm that the value at IN position is 7.5(+1.5)dB greater than
the value at OUT position of Dolby NR switch.
+ Record/playback mode
* Record level control
ws MAX
* Erase the tape with a
bulk tape eraser.
* Input selector---LINE IN
* Record mode
* Record level contro!
-- MAX
* Stop the bias oscillation
by unsoldering point (F)
see fig. 19 on page 12.