Technics RS-M228X - Page 12

RS-M228X
* Noise reduction selector
+++ disc ‘dbx tape
Equipment:
*VTVM * AF oscillator
* ATT * Oscilloscope
* Resistor (600 £2)
@-1 Standard level adjustment in dbx Encode mode
1. Make the connection as shown in fig. 12 and
apply 1kHz —274dB signal from LINE IN. and
set the noise reduction selector to dbx tape
position
Set unit to record mode, adjust ATT so that
the signal level at TP201 (L-CH) and TP202
(R-CH) is 300 mV
Adjust VR205 (L-CH) and VR206 (R-CH) so
that the output signal level at TP203 (L-CH)
and TP204 (R-CH) becomes 300 mV +0.5dB.
dbx circuit board
TP201(L-CH) |
TP202 (R-CH)
TP207 +
Record mode f rye
J
{
tp
1
ITEM ADJUSTMENT
Ps
Tp20siL-cH)
TP204(R-CH)_
VTVM_ Oscilloscope
rsa
JUNE INU | i
600.2 “VR207(L-CHT oo
Resistor { vez08(R-CH) VTVM Oscilloscope
. R205 (L-CH)
Fig. 12 —vR206(R-CH)
@-2 Standard level adjustment in dbx Decode mode
]
2
3
Make the connection as shown in fig. 12 and apply 1 kHz —27 dB signal from LINE IN, and perform
the following adjustments
Set the noise reduction selector to disc position, and adjust ATT so that the signal level at TP201
(L-CH) and TP202 (R-CH) becomes 300 mV
Adjust VR207 (L-CH) and VR208 (R-CH) so that the output signal level at TP203 (L-CH) and
NOTES:
© After adjustments @. @ and @. re-check according to “dbx SYSTEM CHECKING METHOD"
e if the specifications are not satisfied, perform the adjustments again.
TP204 (R-CH) becomes 300mV+0.5dB
CHECKING PROCEDURE FOR PROBLEMS
NOTES: Find defective parts according to the circuit operation checking method given below, and use the results for your reference
during repair. Remember to adjust after repair
Keep good condition, set switches and controls in the following positions, unless otherwise specified
@ Input level controls: Maximum
BB Operation check of
regulated power supply
circuit in dbx circuit
Equipment :
* DC volt meter
* Oscilloscope
G@-1 Check of +10.5V voltage
Make the connection as shown in fig. 13 and
make sure that tne emitter voltage of Q26
is around + 10.5V
OC volt meter
DC volt meter
ITEM CHECKING METHOD
GB-2 Check of —10.5V voltage
Make the connection as shown in
fig. 13 and
make sure that the emitter voltage of Q27
is around — 10.5V
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