Technics RS-M228X - Page 14

RS-M228X
ITEM CHECKING METHOD
@§-2 Operation check of VCA circuit and De-emphasis circuit
1. The procedure is the same as 1 for the above GB-1 VCA circuit
and Pre-emphasis circuit 1201 (L-CH)
2. Short pin @, of IC201 (L-CH) and IC202 (R-CH) to TP207 aaa
(ground) as shown in fig. 17.
3. Set the noise reduction selector to disc position
4. Adjust ATT so that the signal level at TP201 (L-CH) and TP202
(R-CH) is 300 mV.
5. Make sure that the output signals at TP203 (L-CH) and TP204
(R-CH) are sinusoidal. Fig. 17
(The operation of VCA can then be checked.)
6. Change the frequency of input signal to 5kHz and make sure that the output signal level at TP203
(L-CH) and TP204 (R-CH) is decreased by about 12 dB.
(The operation of the De-emphasis circuit can then be checked.)
Connection wire
Operation check of 1. Make the connections as shown in fig. 18. and TP2OLL-CH) 991 «L-cH)
RMS FILTER circuit apply 1OOHz — 27dB signal from LINE IN TP2O2IR-CHY 999 (RCH
(27
Hz—10kHz)
2.
Set
the
noise
reduction
selector
to
disc
position
“VIM
Ose
Condition: 3. Adjust ATT so that the signal level at TP201 TR] Le;
(L-CH) and TP202 (R-CH) is 300 mV
4. Make sure that the emitter signal level of Q221 AF oscillator ak tes
(L-CH) and Q222 (R-CH) is around 300 mV LINE IN
5. Change the frequency of input signal to 5kHz
illoscope
* Stop mode
* Input level controls --- MAX
* Noise reduction selector
+ disc
Equi i and make sure that the emitter signal of Q221
eee
(L-CH)
and
Q222
(R-CH)
remains
at
the
same
VIVM
Oscilloscope
* VTVM * AF oscillator level (300 mV)
* ATT * Oscilloscope Fig. 18
* Resistor (600 Q)
ELECTRICAL PARTS LOCATION
E19 E16