Technics RS-M226 - Dolby NR Circuit Check

RS-M226
ITEM MEASUREMENT & ADJUSTMENT
Equipment : 7. if measured value is not 0.45V, adjust VR5 (L-CH), VR6
+*VTVM _ + AF oscillator (R-CH) (See fig. 1 on).
*ATT * Oscilloscope 8. Repeat from step (2)
+ Resistor (600 2)
» Test tape
(reference blank tape)
-+-QZZCRA. for Normal
@ Fluorescent meter . Test equipment connection is shown in fig. 16.
Condition:
.
As
shown
in
fig.
17,
connect
the
collector
of
Q8 and peak reset terminal.
* Tape selector . Supply 1kHz signal (—24 dB) to the LINE IN
Normal position jack, then press the record button.
+ Input level controls --» MAX _ Adjust the ATT so that the output level at LINE
OUT jack becomes 0.45 V (The input level at
Equipment: ; this condition is termed the standard input Connection
+ VTVM * AF oscillator level) uN cord
* ATT . Adjustment at "—20dB"
A. Adjust the ATT so that input level is —20dB
below standard recording level
B. Adjust VR7 so that the —20dB segment >
lights up in the —20 + 1dB range (L-CH Ly
ONLY) (See fig. 18) SUTETTTTTTETT TTT ET HTT
5.
Adjustment
at
“OdB":
20
(Fak)
6
©
4+
20+
2
00-68:
A. Adjust the ATT so that the output level at Fig. 18
LINE QUT jack becomes 0.45V. MMS
(The input level at this condition is termed vesveseeaserisesisaasssersaseesecsese FOB)
the standard input level.) t SHMUOOUUQUAOUUATOL AUT A UAV ALT AT LAUUHT TUT
. Adjust VR8 so that the +1dB segment 20 (ER) pee nae -2+*0+2 00-628
lights up in the 00.2 dB range of the Fig. 19
* Record mode
Fig. 17
standard input level (See fig. 19). CC
Repeat twice between steps 5 and 6 above. i
. Adjust ATT and check that all segments light SS ITTULTUUEUUMTUUATUUUTOULCUUUU TDCI
vt Pus vrs
PIVTINERYELULASEAS EASE SOEEEEY ET
up when an input signal level is increased to 20 bah airs shee eat
10 dB higher than the standard input level (See ee Fig 20. sc a
fig. 20).
© Dolby NR circuit Dolby circuit frequency response check
Condition: @ Check of the Dolby-B type encoder characteristics
* Record mode . Make connections as shown in fig. 21.
* Dolby NR switch -+- IN/OUT . Set the unit to the record mode. (NR select switch is OUT.)
* Dolby NR select switch . Apply a 1 kHz signal to LINE IN.
++B/C . Adjust the ATT so that the output level at TP3 (L-CH) and TP4 (R-CH) is 12.3 mV.
* Input level controls MAX . The output level at pin 14 should be 0dB.
Equipment: . Set the NR select switch to B, and make sure that the output signal level at pin 14 of IC3 (L-CH) and
*VTVM — * AF oscillator IC4 (R-CH) is +6dB+2.5dB.
* ATT * Oscilloscope . Set the NR select switch to OUT, and adjust the frequency to 5kHz. The output signal level at pin
* Resistor (600 Q) 14 should be OdB. ;
. Set the NR select switch to B and make sure
that the output signal level at pin 14 of IC3 TP3 (L-CH)
(L-CH) and IC4 (R-CH) is 8dB+2.5¢B. re
© Check of Dolby-C type encoder characteristics
9. Repeat steps 1-5 above.
10. Set the NR select switch to C and make sure
that the output signal level at pin 14 of IC3 ;
(L-CH) and IC4 (R-CH) is 11.5dB+2.5dB. fate {ite (L-CH) 2
11. Set the NR select switch to OUT and adjust Ica (R-CH) EN ere
the frequency to 5kHz. The output signal at Fig. 21
pin 14 should be OdB. 9-
. Set the NR select switch to C and make sure
that the output signal level at pin 14 of IC3
(L-CH) and IC4 (R-CH) is 8.5dB+2.5dB.