Technics RS-M228X - Page 10

RS-M228X
dbx SYSTEM CHECKING METHOD
NOTES: Keep good condition, set switches and controls in the following positions. unless otherwise specified.
@ Input level controls: Maximum
ITEM CHECKING METHOD
@ Check for expansion
Condition:
* Stop mode
* Input level controls --- MAX
* Output level control --- MAX
* Noise reduction selector
--- disc/dbx tape
Equipment:
* VTVM * AF oscillator
* ATT * Oscilloscope
* Resistor (600 22)
® Check for standard
level of dbx
Condition
* Stop/record mode
* Input level controls --- MAX
+ Noise reduction selector
++ disc/dbx tape
Equipment:
* VTVM * AF oscillator
* ATT * Oscilloscope
* Resistor (600)
@ Check the frequency
response of the dbx
circuit
Condition
* Stop/record mode
* Input level controls --- MAX
* Noise reduction selector
-+- disc/dbx tape
Equipment:
* VTVM * AF oscillator
* ATT * Oscilloscope
* Resistor (600)
© Output level control: Maximum
® Check for expansion
1. Make the connections as shown in fig. 4 and
apply 1kHz ~ 27dB signal from LINE IN.
and set the noise reduction selector to disc
LINE IN
LINE OUT
[—*
position
AF
oscillator
Adjust ATT, increase input signal level by 10 dB.
and make sure that the reading for VTVM
increases by 20dB+1dB
ATT ¢
6002
Resistor
i :
Stop/record mode yTVM Oscilloscope
Fig. 4
Adjust ATT, decrease the input signal level. and make sure that the reading for VTVM decreases by
20dB+1dB
@®-1 Check for standard level of dbx in dbx Encode mode
1. Make the connections as shown in fig. 5 and
apply 1kHz —274dB signal from LINE IN.
and set the noise reduction selector to dbx
ape position
2. Set the unit to record mode. adjust At T so
that the signal level at TP201 (L-CH) and
TP202 (R-CH) is 300 mV
3. Make sure that the signal level at TP203 (L-CH)
and TP204 (R-CH) is 300mV+0.5dB
AF oscillator
TP201 (L-CH)
VTVM_ Oscilloscope
TP203(L-CH) |=
TP204(R-CH)}! _/
TP202(R-CH) ©
ATT
600
@-2 Check for standard level of dbx in dbx Decode mode
1. Make the connections as shown in fig. 5 and apply 1 kHz —27dB signal from LINE IN. and check as
follows:
TP207-4..[
Record mode
Resistor
LINE IN
dbx circuit board
Fig. 5
2. 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
3. Make sure that the signal level at TP203 (L-CH) and TP204 (R-CH) is 300mV+0.5dB
@-1 Check the frequency response during decoding
1. Make the connections as shown in fig. 5 and apply 1 kHz
— 27 dB signal from LINE IN, and check as follows:
2. Set the noise reduction selector to disc position, and adjust
ATT so that te signal level at TP201 (L-CH) and TP202
(R-CH) becomes 300 mV.
3. With the signal level at TP203 (L-CH) and TP204 (R-CH)
as OdB. change the signal frequency to 1OOHz, 20Hz and
7 kHz respectively. Read signal levels at TP203 (L-CH)
and TP204 (R-CH) and check that they are within the
specifications-1
@-2 Check the frequency response during encoding
1. Make the connections as shown in fig. 5 and apply 1 kHz
— 27dB signal from LINE IN. and check as follows:
2. Set the noise reduction selector to dbx tape position. and
the unit to record mode
3. Adjust ATT so that the signal level at TP201 (L-CH) and
TP202 (R-CH) is 300 mV :
4. With the signal level at TP203 (L-CH) and TP204 (R-CH)
as OdB, change the signal frequency to 1OQHz and 7 kHz
respectively. Read signal levels at TP203 (L-CH) and
TP204 (R-CH) and check that they are within the
specitications- 2.
Specifications-1
| Frequency
Signal levels at
TP2023 and TP204
1 kHz
0.dB (300 mV)
100
Hz —0.5dB* 1dB
20Hz
—30dB+5dB
7 kHz
+7dB+1dB
Specifications-2
Frequency
Signa! levels at
TP203 and TP204
1k Z 0 dB (300 mV)
100
Hz +0.5dB+1dB
7k
z ~ 3.5dB+1dB
NOTES:
e If the results of the above checks @. © and @ do not satisty the specifications, perform the following adjustments
If the specifications are not satisfied even after the adjustments, follow the checking procedure for problems.
¢ lf the output signal is not produced or is extremely distorted, follow the checking procedure for problems