Sony HVR M25U - Professional Video Cassete recorder/player, Service Manual

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6-61
HVR-M25J/M25U/M25N/M25E/M25P/M25C
4. Frequency Characteristic Check
(1) 4CH mode Check
Mode E-E
Signal Audio: 1 kHz, –4 dBs signal
20 Hz, –4 dBs signal
14 kHz, –4 dBs signal
AUDIO IN terminal (CH-1, 2)
Measurement Point AUDIO OUT terminal (CH-1, 2)
Measuring instrument Audio level meter
Oscilloscope
Specified Value Difference in output level:
A = –2 to 0 dB
B = –1.5 to +1.5 dB
Note: 0 dBs = 0.775 Vrms
Switch setting
1) AUDIO MODE (AUDIO SET menu) ......................... FS32K
2) AUDIO INPUT LEVEL switch ....................................... –10
3) AUDIO REC LEVEL control knob
............ The position at –10 dB Check of E-E Level Check
Checking method:
1) Enter 1 kHz, –4 dBs signal to the AUDIO IN terminal (CH-1).
2) Measure the output of AUDIO OUT terminal (CH-1) at this
time, and assume it to be “a” (dBs).
3) Enter 20 Hz, –4 dBs signal to the AUDIO IN terminal (CH-1).
4) Measure the output of AUDIO OUT terminal (CH-1) at this
time, and assume it to be “b” (dBs).
5) Check with the oscilloscope that no clip is found in the output
waveform.
6) Enter 14 kHz, –4 dBs signal to the AUDIO IN terminal (CH-
1).
7) Measure the output of AUDIO OUT terminal (CH-1) at this
time, and assume it to be “c” (dBs).
8) Check with the oscilloscope that no clip is found in the output
waveform.
9) Calculate the difference A (dB) between output levels “b” (dBs)
and “a” (dBs) to check that it satisfies the specified value.
A (dB) = b (dBs) – a (dBs)
10) Calculate the difference B (dB) between output levels “c” (dBs)
and “a” (dBs) to check that it satisfies the specified value.
B (dB) = c (dBs) – a (dBs)
11) For the CH-2, make a checking in the same manner.
(2) 2CH mode Check
Mode E-E
Signal Audio: 1 kHz, –4 dBs signal
20 kHz, –4 dBs signal
AUDIO IN terminal (CH-1, 2)
Measurement Point AUDIO OUT terminal (CH-1, 2)
Measuring instrument Audio level meter
Oscilloscope
Specified Value Difference in output level:
A = –1.5 dB to +1.5 dB
Note: 0 dBs = 0.775 Vrms
Switch setting
1) AUDIO MODE (AUDIO SET menu) ......................... FS48K
2) AUDIO INPUT LEVEL switch ....................................... –10
3) AUDIO REC LEVEL control knob
............ The position at –10 dB Check of E-E Level Check
Checking method:
1) Enter 1 kHz, –4 dBs signal to the AUDIO IN terminal (CH-1).
2) Measure the output of AUDIO OUT terminal (CH-1) at this
time, and assume it to be “a” (dBs).
3) Enter 20 kHz, –4 dBs signal to the AUDIO IN terminal (CH-
1).
4) Measure the output of AUDIO OUT terminal (CH-1) at this
time, and assume it to be “b” (dBs).
5) Check with the oscilloscope that no clip is found in the output
waveform.
6) Calculate the difference A (dB) between output levels “b” (dBs)
and “a” (dBs) to check that it satisfies the specified value.
A (dB) = b (dBs) – a (dBs)
7) For the CH-2, make a checking in the same manner.