Phase Linear 400 Service Information

SECTION |
CIRCUIT DESCRIPTION
Input signal is applied to the base of 0. Тһе out-
put of the differential pair comprised of 91 and 0: is applied
to the base of 04. 94 provides the final voltage gain to drive
the predriver transistors 05 and Qg. The P.N.P. predriver 07
serves
as
a
phase
inverter
to
drive
the
negative
output
driver
transistor Q13- The emitter of 013 drives the paralleled emitter
follower output transistors 014, 915” and 016. Тһе positive
half of the signal is amplified by emitter follower Qg which in
turn drives the paralleled outputs Од, 010, and 012.
Forward bias is generated by bias regulator transistor
Q3. Куд adjusts the slight amount of forward bias necessary to
provide a few milliamps of idling current in the driver transis-
tors. This prevents cross-over distortion.
The protection circuit consists of Ос, Ов, апа their
associated R-C and diode networks. ІЁ the output current flow-
ing through R55 and R3¢ becomes dangerously large, capacitors
Сі2 and Суз acquire a voltage through R53 and R35 to cause 5
and Qg to turn on. 05 and Qç then cause Dg and Dg to also turn
on. Drive current is then shunted through Dg and 95 around the
predriver Qg, preventing an uncontrolled increase in output
current. This prevents Qg from driving the load. D12 апа руз
are
flyback
diodes
which
prevent
overvoltage
from
appearing
across
the
output
transistors
in
the
event
an
inductive
load
is switched. 51 is a switch thermally attached to the heat
sinks.
It
removes
power
if
the
heat
sinks
become
too
hot
to
touch.
SECTION Il
ALIGNMENT
The following adjustment is necessary only for crit-
ical laboratory applications.
Step
#1.
Using
a
voltmeter,
adjust
the
offset
controls
so
that
the
meter
indicates
0
(zero)
volts
at
the
speaker
term-
inals
between
hot
and
ground.
Adjust
as
follows:
Adjust
Rg
offset
for
0
(zero)
volts.
This
completes
offset
adjustments.

Phase Linear 400 Specifications

General

Brand	Phase Linear
Model	400
Category	Amplifier
Language	English