Sony TC-640 Service Manual page 21

| ems Remarks Procedure
18. Overall
Signal-to-
Test Setup:
blank tape
AF osc REC AMP
Mic 7
Noise Ratio
Measurement
LINE OUT jack
NORMAL (standard tape):
7-1/2 ips
(19 cm/s)
3-3/4 ips
(9.5 cm/s)
46 dB 44 dB
SPECIAL (SONY SLH tape):
7-1/2 ips
(19 cm/s)
3-3/4 ips
(9.5 cm/s)
48 dB 46 dB
19. Overall
Distortion
Check
Test Setup:
blank tape
nies REC AMP
MIC jack
aX OUT jack
Specification:
7-1/2 ips: Less than 1.5 %
3-3/4 ips: Less than 2%
—-21—
. Thread a blank tape along the tape path.
. Deliver a 1 KHz signal of —60 dB (0.775 mV) to the
MIC jack.
. Place the unit in the record mode.
. Record the signal for a minute.
. Disconnect the audio oscillator, and terminate the
MIC jack with a dummy resistor of 600 Q.
. Keep the unit in the record mode with no input
signal.
. Playback the signal recorded portion and no signal
recorded portion.
. Make sure that the difference between the two
recorded portions of the tape is more than the
specification.
Note:
When using an SLH tape, set the TAPE
SELECT SWITCH to SPECIAL.
. Thread a blank tape along the tape path.
. Deliver a 1 kHz signal of ~60 dB (0.775 mV) to
the MIC jack.
. Place the unit in the normal record mode.
. Check the reading on the distortion meter.