While the SB-
10
was designed
primaril.y for
use
with the Heathkit Models
DX- 100, DX-
1008, and
TX-1 as a complete SSB
transmission
capability,
lt can be used to excite
higher
power
linear
amplifiers by itself
or in conjunction
wj.th
the companion transmitter.
Any
grounded
cathode
linear
amplifier
requiring
10
watts
PEP or
less drive can be driven directly
by the SB-10
and
any
grounded grid
iinear amplifier
may be
driven to
full
output with the SB-10 and
TX-1 com-
bination. When
driving a linear
amplifier
directly with the SB-10. a
companion transmitter
must still be used
to supply
power
and RF
excitation at
the fundamental frequency. However,
under
these
conditions, a much
lower
power
AM-CW transmitter
may be used since
the
final
ampli.fier of the companion
transmitter
would
not
be utilized. Care
must
be
taken to
observe
the limitation of
plate
and
fiiament
power
that
such a transmitter would be capable
of supplying
to the SB-10. The
use of a separate
power
supply
for
the SB-10, would be advisable
under
a
condition
such as
t his.
IN CASE
OF
DIFFICULTY
Mistakes
in wiring are the most
common
cause
of difliculty. Consequently,
the
first
step
ls to
recheck all wiring
against the
pictorials
and
schematic diagrams. Often
having a
lriend check
the wiring
will locate an
etror consistently
overlooked
With miniature sockets,
there
is a
possibility of shorts between adjacent socket
terminals
due
to the close spacing.
This should
be checked
and
if
anv doubt
exists, the terminals should
be
pried
apart until
obvious spacing
can be
seen between them.
Sometimes apparently
good
solder
connections
will have an insulatiig coating of rosin between
the wire. the terminai.
and the
solder.
This
is often
the
case when insufficient heat
was applied
in solderlng. An
ohmmeter check
of any
questionable connections will test
for
this
condition.
Al1 voltages
should be
"off"
for such
tests.
If the
fuses in the transmitter
blow
consistently
when the
function
switch is
placed
either
in
MAN UAL or VOX.
check the
resistance
to
ground
at
pin
6 of the
power plug
with all
power
off
and the
function
switch
in MANUAL.
A
reading
of
about
40 KQ
should
be obtained.
A
shorted
filament lead
will be
revealed
immediate
ly by burning
in
sulation on
the affected lead
plus faiiure
of
the
tubes affected to
light.
If some
difficulty
persists
after
the
steps
outlined
have
been
completed,
attempt
to localize
the
irouble to
a
pariicular
stage
in the
adapter
citcuit.
Be sure
to re-read
the circuit
description
on
pages ? and 8 so that,'cause
and
effect"
reasoning
may
be employed
as the s.arch
for trouble
prog.i"""".
Use
the tuning
procedure and
the
voltage chart
on
page
59 as a basis
for
localization
inO-refer to
the block
diagram
and
schematic
tovisualize
circuit relati.onships.
The
panel
tuning
meter will
also aid
in locating
trouble.
ff
no
SB-10
meter
reading
can
be obtained
under
any condition,
check the
connecting
coaxial
cables
for
possible
shorts
plus
the
internal
coaxial
cable runs. Check
the
bandswitch
wiring
on
all stages
for errors
or short
circuits.
Measure
the voltages
on the
6CL6 and
6BQ5 tubes
to
insure"proper
operation
ol
these
stages.
Inspect
theRF inpui
connections on the
balanced
mod-
ulator
sub-chassis"
Checking
the RF
input connections,
RF
phase
shift
networks. and balanced
modulator
voltages
nr"y
""q.,ir"
."moval.
of thefrontpanel
and
chassis
apron. To
remove samei
remove
the micro-
phone
cor.rnector
and
unsolder
the
center
conductor,
remove
both the
audio
gain
control
and
function
switch,
and remove
all the
front
panet
knobs.
Now remove the
four #6 sheet
metal
screws hold-
ing
the front apron
to the
chassis
and
slide
the
panel
andapron
off the
control shafts.
Operation
fci test
pu.poies
wlth the
front
panel removed.
is
possible
by
providing
a
ground return to the
chassis
for the
function switch
and
reconnecting
the inner
conductor of
the microphone
input
cable to
the connector.
Page
58
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