Sony RMT-V298A, Service Manual

Page: 59 / 79

7-4
3. Overall Level Characteristic and Distortion Factor
Check
Purpose:
Check the record level, play level, and distortion factor against the
reference input.
Mode REC and PB (SP mode)
Signal 400 Hz, –7.5 dBs
Measurement point Audio output terminal
Measurement equipment Audio level meter and
distortion factor meter
Specified value Playback level: –7.5 ± 2.0 dBs
Distortion factor: 1% or less
Confirmation Method:
1) Supply an audio signal of 400 Hz, –7.5 dBs simultaneously to
both L and R channels of Audio Line Input.
2) Make recording
3) Play back a recorded portion.
4) Confirm that a playback level is –7.5 ±2.0 dBs.
5) Confirm that a distortion factor is within 1%.
4. Overall S/N Check
Purpose:
Confirm that the S/N is within the specification.
Mode REC and PB (SP mode)
Signal Short
Measurement point Audio output terminal
Measurement equipment Audio noise meter
Specified value –67.5 dBs or less
Confirmation Method:
1) Connect both L and R channels of audio line input to the GND.
2) Start recording.
3) Play the recorded part to confirm that the noise is below –67.5
dBs.
2-4-2. Normal Audio System Adjustment
• Make adjustment in the SP mode, unless otherwise specified.
Use a normal VHS cassette for an adjustment tape.
• Set AUDIO MONITOR to normal.
[Adjustment Sequence]
1. ACE Head Adjustment
2. E-E Output Level Check
3. Frequency Response Check
4. Overall Level Characteristic and Distortion Factor
Check
5. Overall S/N Check
1. ACE Head Adjustment
Refer to the SERVICE MANUAL of VHS MECHANICAL AD-
JUSTMENT VI.
2. E-E Output Level Check (SLV-ED15/ED25/ED33/
ED39/ED55/ED66/ED85/ED88/ED89/EZ11/EZ22/
EZ44/EZ66/EZ77)
Purpose:
Confirm that the output level against the reference input is within
the specification.
Mode E-E
Signal L, R: 400 Hz, –7.5 dBs
Measurement point Audio output terminal
Measurement equipment Audio level meter
Specified value –7.5 ± 2.0 dBs
Confirmation Method:
1) Simultaneously input a signal of 400 Hz, –7.5 dBs to both L
and R channels of Audio Line Input.
2) Confirm that the audio output level is –7.5 ± 3.0 dBs.
(This level only can appear with mono models)
3. Frequency Response Check
Purpose:
Confirm that the frequency characteristic is within the specifica-
tion.
Mode REC and PB (SP mode)
Signal 400 Hz, –17.5 dBs
7 kHz, –17.5 dBs
Measurement point Audio output terminal
Measurement equipment Audio level meter
Specified value 0 ± 4 dB
Tape path adjustment must have been completed.
Confirmation Method:
1) Supply a signal of 400 Hz, –17.5 dBs to both L and R chan-
nels of Audio Line Input.
2) Connect the audio level meter to the Audio Line Output.
3) Adjust the attenuator so that the audio level meter will indi-
cate –17.5 dBs.
4) Make recording in the SP mode.
5) Set an audio line input signal to 7 kHz and make recording.
6) Playback a recorded portion, and measure output levels at 400
Hz and 7 kHz.
7) Confirm that the 7 kHz playback output level within a range
of the 400 Hz playback output level 0 ± 4 dB.