Crown DC-300A - 5.6 TEST PROCEDURES; 5.7 TROUBLESHOOTING

18
A current limiter will not yield to the load but will sus-
tain the constant current demands of the inductive load
without flyback.
Early amplifier designs frequently employed fixed
current limiters but had serious difficulty with obtain-
ing reliable low frequency output while being capable of
full-voltage 4 ohm output. Also, many earlier designs
used fragile epi-base or triple diffused outputs, which
for reliable performance are poor mates for a current
limiter protection scheme. The DC-300A uses eight
150W
hometaxial*
silicon
power
transistors
per
channel,
which
are
the
toughest
type
of
audio
power
transistor
yet
developed.
Their
toughness
allows
the
reliable
use
of
a
current
limiter
which
when
rendered
signal
variable
permits
larger
power
outputs
than
would
be
safely
allow-
able
with
a
current
limiter
of
fixed
type.
At
subsonic
frequencies,
the
SPACE
control
behaves
as
a
VI
limiter
and
provides
the
increased
protection
needed
at
DC
to
prevent
destruction
due
to
heat
buildup
in
the
half
of
the
output
stage
that
is
being
driven.
*Tradename of RCA
NOMINAL LIMITS OF VI OUTPUT
DISCLOSURE
PROHIBITED
ut
effective Nov. 4, 1974
@@@ AC LINE FUSE BLOWS
(OC SINGLE CHAN.) BLOWS
AT 10A DC IF BOTH
CHANNELS ARE DRIVEN EQUALLY
= = MID-FREQUENCY BURST LIMIT
XXX SHORT CIRCUIT CONTINUOUS LIMIT
AREA OVER WHICH LIMITER (AC)
VARIES (SIGNAL DEPENDENT)
<@@@ MAX. AC (LIMIT (2), V OUT (SINE) AT
MAX.)
MAX. CONT. AC POWER
@, = 2.75)
emmcm= HIGH FREQUENCY LIMIT
FIG. 3-2
GRAPH OF VI OPERATING RANGE OF DC-300A OUTPUT