Sony TC-640 Service Manual page 24

. Set the MONITOR switch to TAPE.
. Set the PB VOL controls to the specified position
on page 12.
. Deliver a 1 kHz signal of —60 dB (0.775 mV) to
the L-CH (R-CH) MIC jack only.
. Rewind the tape to the beginning.
. Set the SOS & ECHO switch to SOS.
. Place the R-CH (L-CH) only in the record mode.
. Check to see that R-CH (L-CH) output level
becomes the same as L-CH (R-CH) output level by
adjusting the SOS & ECHO VOL control.
25. ECHO Check . Thread a blank tape along the tape path.
. Set the SOS & ECHO switch to ECHO.
. Deliver a 1 kHz signal of —60 dB (0.775 mV) to
the MIC jack.
. Place the unit in the record mode.
. Check to see that echo level increases as the SOS &
ECHO VOL control is turned clockwise.
. Check to see that oscillation does not occur when
turning the PB VOL control! fully clockwise.
Note:
The adjustment is required for both channels.
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