Marantz 3800 - Trouble Analysis and Isolation

(1)
(2)
(3)
(4)
(1)
(2)
(1)
(2)
(3)
DOLBY
VU
METER
CALIBRATION
Set
Meter
Switch
to
left
channel.
Ensure
all
switches
and
controls
are
set
as
listed
in
Paragraph
3D
(Decode
Loop
Gain).
Apply a 100 Hz signal to the AUX IN-
PUT Jack, and adjust the amplitude for
580 mV as measured at the junction of
Pin No. 82 and J104.
Adjust
Meter
Calibration
R706
for
0
VU
indication
on
the
Dolby
VU
Meter.
400
Hz
TONE
OSCILLATOR
ADJUSTMENT
Set the DOLBY Switch to any DOLBY
Mode position such as REC lI.
Depress the 400 Hz TONE Switch and
adjust Tone Oscillator Control R702 for
a 580 mV rms signal as measured at the
TAPE | OUTPUT Jack.
MULTIPLEX FILTER ADJUSTMENT
Set DOLBY Switch to PLAY.
Apply a 1 kHz signal to the AUX INPUT
Jack and adjust the amplitude to 580 mV
rms as measured at the TAPE | OUTPUT
Jack.
Reset oscillator frequency to 19 kHz and
adjust Filter Trap (choke) L503 for mini-
mum output. When properly adjusted, the
output level at the TAPE OUTPUT Jack
will be a minimum of 18 mV below the
level of the 1 kHz reference signal.
No primary power consumption
Excessive primary power consumption
No signal output both channels
L.
BIAS
FILTER
ADJUSTMENT
(1)
Set
the
DOLBY
Switch
to
REC
I,
PLAY
CAL
(cw)
and
Record
Switch
(cew).
(2)
Apply
a
1
kHz
signal
to
the
AUX
IN-
PUT
Jack
and
adjust
the
amplitude
for
0
VU
indication
on
the
Dolby
VU
Meter.
(3)
Reset
oscillator
frequency
to
100
kHz
and
adjust
Filter
Trap
(choke)
L505
for
mini-
mum
output
measured
at
the
PREAMP
OUTPUT
Jack.
When
properly
adjusted,
the
output
level
of
the
100
kHz
signal
will
be
at
least
40
dB
below
the
output
level
of
the
1
kHz
reference
signal
at
the
PREAMP
OUTPUT
Jack.
4. TROUBLE ANALYSIS
The
partial
list
of
possible
malfunctions
and
causes
listed
in
Table
2-2
enables
locating
troubles
that
may
be
difficult
to
isolate.
Normal
trouble-
shooting
techniques
(point-to-point
signal
tracing
and
oscilloscope
analysis)
are
assumed
in
isolating
problems.
NOTE:
Performance
verification
tests
are
necessary
following
any
repair.
Table
2-2
lists
possible
symptoms
and
causes
if
a
Model
3800
malfunctions.
We
do
not
attempt
to
point
up
all
potential
problems
and
their
remedies
since
the
service
technician
is
capable
of
recogniz-
ing
most.
We
attempt
to
aid
the
service
technician
in
isolating
problems
from
the
unit
level
down
to
a
detail
part.
All
references
in
this
section
will
be
made
to
Figures
1-2
and
3-9.
-
Open
A.C.
input
circuit,
line
cord,
fuse,
power
switch
or transformer
.
Power
supply
circuit
defective
.
Short
in
A.C.
input
circuit
—
.
Short
in
A.C.
secondary
circuit,
pilot
lamp
circuit,
or
power
supply
No
D.C.
supply
voltage
to
amplifiers,
+Vcc,
-Vcc
or
neither,
caused
by
broken
supply
lines,
defective
Power
supply
lines
or
defective
power
transformer
Table 2-2 Trouble Analysis
213