Heathkit W-5M User Manual

Power supply
regulation,
output
transformer design and
careful shaping of the overall frequency
response
curve
all
play very
important
parts in the
ability of the
amplifier to recover
quickly
when overloaded.
There is
no
simple
or
easy
way
to specify the
overload
recovery
capability
and
the problem
is made more
complicated
by
the transient nature of the
condition.
In
order to
present
a meaningful specification,
we
have resorted to oscillograms
of simulated conditions
which
are known to
create
the condition.
These are shown directly below.
The
test signal
shown in oscillogram
F is
a composite of three
signals
as
defined
in
the sketch
below:
«
50 MS
H-3MS*!
ThelOkc
component represents normal mixed
program
material.
The heavy
7 millisecond
rec-
tangular pulse simulates an overloading
transient of sufficient length to
show
up
any "ringing"
or "hangover"
effect
following the
sharp
rise in signal
level.
The short 200
microsecond pulse
follows
this component after
3
milliseconds.
This
pulse could
be
placed at any
point on the wave-
form.
Its purpose was to
determine if overload recovery
was
sufficient
to
faithfully
present
a
short
transient immediately
following
overload. The composite test
signal
is
shown
in oscillo-
gram
F.
(Again, remember that the upper trace is the
input signal; the lower trace
is
the
output
of
the amplifier.)
In
order to
show
the critical portion of the cycle more
clearly, oscillogram
G
is
a
5
times
expansion
of the trace.
Vertical sensitivity of
the
lower trace
of the oscilloscope
was
20
volts per centimeter
or approximately 20 volts peak-to-peak. Under
these conditions
,
the amplifier
is
operating safely below the
overload
point.
At
H,
the same
test
signal
has
been
increased
in
amplitude;
the
amplifier
is now trying
to pro-
duce
an
output signal
of some
40 volts
peak-to-peak. Again,
J
represents
a
5
times
expansion
of the same
condition.
Observe
at
H,
that the
overloading
transient
has
completely
lost its identity
because
of output
limitation. However,
the
recovery
of the
amplifier
is
smooth and
gradual,
without
hangover
or
ringing.
The
short pulse is reproduced
faithfully, even
during the
gradual
recovery,
which
is
particularly
important.
This
effect is
shown
quite
plainly
at
J.
Page
8

Heathkit W-5M Specifications

General

Brand	Heathkit
Model	W-5M
Category	Amplifier
Language	English