Marantz PM500 - Page 7

TOTAL HUM AND NOISE TEST
. With shorting plugs connected to the Phono input
jacks and an 8 ohm resistive load connected across
the speaker system output terminals, connect a dis-
tortion analyzer across the load.
NOTE:
If the distortion analyzer does not contain a built-in
voltmeter, an AC VTVM may be substituted.
. Set the distortion analyzer controls for voltge
measurements and apply power to the amplifier.
Set the volume control fully CCW. Set the
SELECTOR switch to PHONO.
. If the distortion analyzer indicates more than 1.0 mV
refer to the trouble analysis section of this manual.
. Set the volume control fully CW. If the distortion
analyzer indicates more than 15 mV, refer to the
trouble analysis section of this manual.
MAXIMUM POWER OUTPUT
. Connect the audio oscillator to the AUX input. Set
audio oscillator frequency to 1 kHz. Set SELECTOR
switch to AUX.
. With the distortion analyzer connected across the
output load (8-ohm), set the analyzer on the 30 VAC
scale.
. Turn the analyzer on and increase the audio oscillator
output to 150 mV. The AC VTVM should read 23.6
VAC {20 VAC For Model PMS50O0 only) or more.
E. HARMONIC DISTORTION TEST
1. Set the frequency of the audio oscillator and the
distortion analyzer to 20 kHz.
2. Set the controls of the analyzer for voltage measure-
ment on the 30 volt scale.
3. Adjust the audio oscillator output level until the
analyzer meter indicates 23.6 VAC. (20 VAC For
Mode! PM500 only)
4.
Switch
the
distortion
analyzer
to
Set
Level
and
adjust
SENSITIVITY
for
full
scale
reading
on
0
~
0.1%
scale.
5.
Measure
the
total
harmenic
distortion
with
the
analyzer
and
verify
it is
less
than
0.03%.
NOTE:
Any
parasitic
oscillation
in
the
amplifier
will
be
displayed
on
the
oscilloscope
when
capacitance
is
switched
into
the
load.
6.
Switch.
the
distortion
analyzer
back
to
SET
LEVEL.
(Do
not
readjust
sensitivity
of
analyzer.)
7.
Change
the
frequency
of
the
audio
oscillator
and
dis-
tortion
analyzer
to
1
kHz.
Adjust
audio
oscillator
output
for
a
full
scale
reading
on
the
0
~
1%
scale.
8.
Measure
the
distortion,
verifying
it
is
no
greater
than
0.03%,
9.
Repeat
steps
7
and
8,
changing
frequency
to
20
Hz.
Distortion
should
be
no
more
than
0.03%.
10.
Check
for
parasitic
oscillation;
there
should
be
none.
CAUTION (For Model PM700 only)
PM700 Heat-loop type Cooling System
The Model PM700 uses a heat pipe loop’ to cool power
transistors. At the bottom of the pipe loop, the Freon
enclosed in evaporatively cools the power transistors,
then moves through the pipe to be cooled and liquefied
by cooling fins.
The Freon liquid drops back to the bottom of the pipe
loop, to continue the cooling cycle.
The heat loop is designed to give best performance when
4-00135 / DRUCK 1
the PM700 is properly set. However, in a case of repair
Or measurement, approximately the same performance
can be obtained if the PM700 is set up as shown in the
following figures. If the inclination of the case exceeds
the maximum value shown below, the liquefied Freon
cannot return to the bottom of the pipe loop and the
_ convection cycle ceases, so that transistors are not cooled,
resulting in problems from overheating.