Marantz 4100 - BTL Connection; Power Supply Unit; Trouble Analysis; Excessive line consumption

‘to
limit
current
or
to
contro!
the
power
transistors
so
that
do
not
operate
beyond
the
safety
area.
In
case
either
excessive
current
flows,
or
the
load
becomes
almost
entirely
reactive,
in
the
power
stage,
the
transistors
H607
and
H609
and
the
diodes
H622
and
H624
are
operated
through
the
resistors
R642
and
R644,
so
that
the
power
transistors
are
protected
from
damage.
7.
BTL
(Balanced
Transformerless)
CONNECTION
This
power
amplifier
is
designed
to
operate
in
either
2-channel
or
4-channel
modes,
depending
on
the
setting
of
the
AMPLIFIER
MODE
switch
that
incorporates
phase-conversion
and
power
switch
for
BTL
connection.
With
this
switch
placed
in
the
25Wx4
position,this
unit
operates
as
a
25W.4channel
amplifier.
With
the
switch
placed
in
the
GOWx2
position,
the
unit
operate
as
a
GOW
2
channel
amplifier,
in
which
case,
the
power
output
is
obtained
only
from
REAR
SPK
terminals.
The
transistor
H626
convert
the
phase
of
1
channel
amplifier
and
3
channel
amplifier.
8.
POWER
SUPPLY
UNIT
The
power
supply
unit
consisting
of
the
transistors
H801
and
H802,
operating
as
an
auto-
matic
voltage
regulator,
provides
+35V
DC
to
all
the
amplifiers
except
the
main
amplifier.
The
transistors
H803,
H804
and
H805
operate
the
relay
L801
that
protects
speakers
from
destruction,
and
has
a
time
lag
of
from
three
to
five
seconds,
for
other
transistors
to
work
stably.
9.
TROUBLE
ANALYSIS
1.
Excessive
line
consumption
a.
Check
for
shorted
H851
through
H854,
C003,
C004.
b.
Check
for
shorted
transistor
HOO1
through
HO08.
Check
LOO1
for
short.
2.
Noline
consumption
or
zero
bias
a.
Check
line
cord,
fuse,
shorted
H581,
H582.
b. Check for open rectifiers H851 through
H854, or open L001.
3.
Excessive
hum
and
noise
a.
Check
filter
capacitors
C003,
C004,
H801,
H802.
4.
Parasitic
oscillation
a.
Check
for
defective
C607,
C608,
C619,
C620,
C621,
C622.
10.
POWER
AMPLIFIER
ADJUSTMENT
1.
Connect
a
VTVM
between
J629
and
J613
and
adjust
the
trimming
resistor
R628
until
the
VTVM
reads
10mV
DC.
For
the
other
channel,
connect
the
VTVM
between
J630
and
J614
and
adjust
the
R629
for
the
same
reading.
2.
Connect
a
VTVM
between
J623
and
J629
and
adjust
the
trimming
resistor
R613
until
the
VTVM
reads
OV
DC.
For
the
other
channel,
connect
the
VTVM
between
J623
and
J630
and
adjust
the
trimming
resistor
R614
for
the
same
reading.
11. POWER SUPPLY ADJUSTMENT
Connect
a
VTVM
between
J802(—)
and
J804(+)
and
adjust
R806
until
the
VTVM
reads
35.0V under no signal condition.
12. METER ADJUSTMENT
Connect
the
audio
oscillator
to
the
AUX
input,
set
audio
oscillator
frequency
to
1KHz.
Set
SELECTOR switch to AUX.
2.
With
the
distortion
analyzer
connected
across
the
output
load
(8-ohm),
set
the
analyzer
on
the
30V
AC
scale.