Harris MW-1 Reference manual

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J)HARRIS
MW-1
Bulletin
No
.
AM-114-LAP
Equipment:
Date
6-10-77
This
Service
Bulletin
is
issued
as
a
"State-of-the-Art"
up-date
for
the
MW-1
transmitter.
It
is
recommended
that
the
enclosed
information
be
reviewed
by
the
station
engineer
since
these
product
improvements
may
have
been
included
in
your
transmitter.
Hence,
not
all
modifications
enclosed
herein
are
applicable
to
your
station.
Since
there
is
an
industry
wide
shortaRe
of
parts,
we
recommend
that
where
possible,
parts
be
obtained
locally
or
possibly
be
already
on
hand
at
the
station.
I.
IMPROVE TRANSMITTER GROUNDING
Wide
differences
in
transmitter
installations
indicate
that
superior
grounding
techniques
must
be
employed
for
equipment
protection
and
reliability.
A.
Add
a
one
inch
wide
copper
or
aluminum
ground
strap
rom
the
back
to
center
of
the
PA
module
deck
support
bracket
crossmember,
at
the
back
of
the
transm
tter.
Attach
the
other
ena
to
any
open
position
at
the
back
center
of
the
loading
coil
assembly
deck's
bottom.
A
~ggested
grounding
location
would
be
as
viewed
Trom
the
back
of
the
transmitter,
just
in
front
of
the
center
point
of
the
C-1
capacitors.
{Section
I-A)
B.
Continue
the
ground
strap
on
the
left
rear
side
of
~he
transmitter
cabinets
from
-the
PA
deck
assembly
to
th.P.
bottom
of
the
output
loading
deck
assembly
above.
We
suggest
a
one
or
two
inch
wide
copper
strap.
Attach
strap
with
any
8-32
or
similar
bolts
on
hand
at
the
station.
(Bottom
Picture;
Section
I-B)
II.
AUDIO DRIVER ASSEMBLY
A-17
(992-4206-001)
A.
R.
F.
I.
in
Audio
1.
Change
C-2
(1,000
pf,
500V)
to
2,000
pf
capacitor
(Harris
Part
Number
500-0845-000).
HARRIS
CORPORATION
P.O.
Box
4290,
Quincy,
llllnols
_
62305
217
/222
-
8200
112-437-0610

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-- v2 .
Change
R-17
(27
ohm
2W)
to
a
240
ohm
2W
resistor
(Harris
Part
Number
540-0596-000).
B.
Zener
diode
CR-3
heat
sink
improvement.
Remove
split
•
lock
washer
from
under
CR-3
located
on
heat
sink
be-
neath
A-17
PC
board.
III.
REMOTE
PA
CURRENT
AMPLIFIER,
A-22
ASSEMBLY
(992-4213-002)
A.
Variation
of
Remote
PA
current
metering
during
modulation.
1.
Add
capacitor
between
terminals
21
and
22.
Use
any
10
volt
electrolytic,
tantalum
or
paper
capacitor.
We
suggest
a 1
to
50
mfd
capacitor.
IV.
PA
MODULES
(992-4201-001)
SERVICE INFORMATION
A.
Testing
with
sine
wave
tones.
1.
It
has
come
to
our
attention
that
some
extremely
long
and
continuous
test
procedures
are
being
used
for
Distortion
and
Response
testing.
We
recommend
that
when
testing
the
transmitter's
audio
quality
above
5
kHz
at
full
modulation,
that
such
testing
should
be
of
short
duration
to
reduce
stress
on
components.
V.
AUDIO
PAD
CHANGE,
A-18
ASSEMBLY
(992-4205-001)
A.
600
Ohm
termination
resistance
changes
when
switching
between
High/Low
power
levels.
1.
Change
configuration
of
Audio
11
H
11
pad.
Review
attached
drawing
and
overall
drawings
in
Instruc-
tion
Book.
Remove
one
end
of
100
ohm
R-19
resistor.
Add
resistor
Rx
for
your
power
level
between
freed
end
of
R-19
and
PC
board.
At
K-3A,
re-arrange
audio
wire
number
150
as
per
drawing.
Add
shielded
single
conductor
cable
from
the
junction
of
R-19
and
Rk
to
relay
K-3A
as
shown
in
drawing.

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MW-1
Field
Service
Bulletin
AM-114-LAP
PA
Module
Deck
Ground
Strao
{Section
I-A)
Main
Cabinet
Ground
Strap
{Section
I-B)