Frequency Characteristic Check - Sony DSR-25 Service Manual

4. Frequency Characteristic Check

(1) 4CH mode Check
Mode STOP
Signal Audio: 1 kHz, –6 dBs signal
Measurement Point AUDIO OUTPUT terminal
(CH-1, 2)
Measuring instrument Audio level meter
Specified Value Difference in output level:
Note 1: 0 dBV = 1 Vrms
Note 2: 0 dBs = 0.775 Vrms
Switch setting
INPUT LEVEL select switch .......................... –10
Menu setting (AUDIO SET menu)
AUDIO MODE ................................................ FS32K
Checking method:
1) Enter 1 kHz, –6 dBs signal to the AUDIO INPUT terminal
(CH-1).
2) Measure the output of AUDIO OUTPUT terminal (CH-1) at
this time, and assume it to be "a" (dBV).
3) Enter 10 Hz, –6 dBs signal to the AUDIO INPUT terminal
(CH-1).
4) Measure the output of AUDIO OUTPUT terminal (CH-1) at
this time, and assume it to be "b" (dBV).
5) Enter 14 kHz, –6 dBs signal to the AUDIO INPUT terminal
(CH-1).
6) Measure the output of AUDIO OUTPUT terminal (CH-1) at
this time, and assume it to be "c" (dBV).
7) Calculate the difference A (dB) between output levels "b"
(dBV) and "a" (dBV) to check that it satisfies the specified
value.
A (dB) = b (dBV) – a (dBV)
8) Calculate the difference B (dB) between output levels "c"
(dBV) and "a" (dBV) to check that it satisfies the specified
value.
B (dB) = c (dBV) – a (dBV)
9) For the CH-2, make a checking in the same manner.
10 Hz, –6 dBs signal
14 kHz, –6 dBs signal
AUDIO INPUT terminal
(CH-1, 2)
A = –4 to 0 dB
B = –1.5 to +1.5 dB
(2) 2CH mode Check
Mode
Signal
Measurement Point
Measuring instrument
Specified Value
Note 1: 0 dBV = 1 Vrms
Note 2: 0 dBs = 0.775 Vrms
Switch setting
INPUT LEVEL select switch .......................... –10
Menu setting (AUDIO SET menu)
AUDIO MODE ................................................ FS48K
Checking method:
1) Enter 1 kHz, –6 dBs signal to the AUDIO INPUT terminal
(CH-1).
2) Measure the output of AUDIO OUTPUT terminal (CH-1) at
this time, and assume it to be "a" (dBV).
3) Enter 20 kHz, –6 dBs signal to the AUDIO INPUT terminal
(CH-1).
4) Measure the output of AUDIO OUTPUT terminal (CH-1) at
this time, and assume it to be "b" (dBV).
5) Calculate the difference A (dB) between output levels "b"
(dBV) and "a" (dBV) to check that it satisfies the specified
value.
A (dB) = b (dBV) – a (dBV)
6) For the CH-2, make a checking in the same manner.
5-69
STOP
Audio: 1 kHz, –6 dBs signal
20 kHz, –6 dBs signal
AUDIO INPUT terminal
(CH-1, 2)
AUDIO OUTPUT terminal
(CH-1, 2)
Audio level meter
Difference in output level:
A = –1.5 to +1.5 dB
DSR-25