Sharp GF-777H - Page 13

Oscilloscope
Recording input socket (external) microphone
input socket, line/phono input socket and mixing
microphone socket
Audio generator Attenuator
©
Record mode
R453 or
R454
Figure 13-1
Record Amplifier Sensitivity Check
1) Connect a VTVM to both ends of the resistor (R453 or
/ a Baa Sockets Inputs
R454) on the record/playback amp. printed wiring board. =
2)
Short
pins
@
and
©
at
the
secondary
side
of
the
bias
External
microphone
input
ae
feed
oscillation
coil (L801)
to
stop
the
oscillation.
~
3)
Set
the
function
selector
switch
to
“‘tape’’
and
the
deck-2
Mixing
microphone
eae
saute
tape
selector
swtich
to “‘normal”
position.
vos
4) Place the unit in record mode, and check if the VTVM Line input 0.06V ~0.13V
reading becomes 0.2mV with the respective inputs tabu- (—21 +3dB)
lated below — the input oscillation frequency is set to Ear 1.0mV ~ 2.0mV
1 kHz and 0 dB = 1 V is assumed. pana (—57 +3dB)
Note:
For the input to the external microphone input socket, it
must be applied across the right and left channels. se raiiceies
Input sockets VM,
Playback Amplifier Sensitivity Check
1) Connect a VTVM, across a 4 ohm resistor, to the external Audio generator Attenuator Record mode
speaker socket.
2) Set the function selector switch to “‘tape’’, the treble/bass
tone control knob to “‘center’’ and the volume control
knob to ““10/max.”’ position.
R453 or R454
Figure 13-2
3) Reproduce a test tape (TEAC, MTT-118, 1 kHz,
250 pWb/mm, —10 dB prerecorded).
4) At the time, the VTVM must read approx. 2.0V.
5) Then connect the VTVM to the line output socket and the welt Sicaiodses
deck-1 monitor output socket in order, then the VTVM socket, line output _V.T.V.M,
reading must be approx. 200mV for the former, and
approx. 10mV for the latter.
Playback mode
Test tape
MTT-118
Note:
For
measuring
the
output
from
the
deck-1
monitor
output
socket,
the
test
tape
be
played
through
the
use
of
the
Record/Playback
lead * Line
socket or deck-1
monitor output
socket
* External speaker socket; 4 ohms
output socket; 50K ohms
+ Deck-1 monitor output socket; 8 ohms
deck-1.
Figure
13-3
Record/Playback Sensitivity Check
1)
Connect
a
VTVM,
across
a
4
ohm
resistor,
to
the
external
main
speaker
socket.
2)
Set
the
function
selector
switch
to
“tape”,
the
deck-2
tape
selector
switch
to
“normal”,
the
treble/bass
tone
control
knob
to
“center”,
the
volume
control
knob
to
“*10/max.””,
©)
the
recording
level
control
knob
to
“max.”
and
the
Audio generator Attenuator
External microphone input sockets
Record mode Record/Playback
head
Normal tape
MTT-502
recording
mode
selector
switch
to
“manual”,
position.
3)
Connect
an
audio
generator
to
the
external
microphone
input
sockets
of
both
channels,
and
apply
a
1
kHz
signal
of
output
level
—78dB
(0.126
mV,
0dB
=
1V)
to
these
sockets
at
a
time.
4)
Record
this
signal
on
a
normal
tape
(TEAC,
MTT-502).
5)
Reproduce
this
recorded
tape,
then
the
VTVM
must
read
Oscilloscope
Playback mode
External speaker socket
approx.
1.5
V.
Figure
13-4