Sharp VC-780E Service Manual page 40

VL-/6U
VC-790ET
*
- | Sound ts distorted. *
The reasonance in the recording or :
" 1 playback ts incorrect. :
- Problems
The picture collapses when the tape
recorded by oneself is played back.
Noises appear on the whole of picture
when the tape recorded by oneseif is
played back.
Noises is noticeable at E-E mode or
when the tape recorded by oneself 1s
played back.
Noises appear on the picture when
the tape is played back with
Standard tape.
Tape does not run.
There appears no sound at playback
mode.
Recording is impossible.
Noise and hum appear frequently
during playbak or recording.
"The audio head is defective.
Check if there is a normal voltage at teach pinof
the head amplifier.
Check the video head or replace it a new one.
Check if there is a normal voltage at each pin of
the head amplifier.
Check the video head or replace it a new one.
The tuner and/or RF converter are defective.
Check if AT 5V is applied at pin 9 of the RF
converter.
Check the coaxial cable between the tuner and the
RF converter for breakage.
Disonnect the antenna cable to see if the DC
voltage at the tuner's AGC terminal goes above 6V.
Check each voltage and motor unit of capstan
motor drive circuit. /
Clean the video head or replace it a new one.
First make sure the E-E picture appears as specified.
(If not, the muting effect is produced.)
ALC at [C601 operates improperly.
Check if there is audio signal at pin 17 of IC601.
The audio muting circuit is defective.
Check if the control signal is applied. (If not, the
muting effect is produced.)
Check if playback audio signal is applied to pin 7 of
IC601 and goes out of pin 17.
The audio head is magnetized or defective.
Bias current is insufficient.
The audio head is magnetized or defective.
Bias oscillator circuit is defective.
Bias oscillator circuit is not normally functioning.
Check if pin 12 of Audio module (bias control 9V)
is at high level.
The audio head is defective.