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Check
for proper
drive level (250mV)
and verify that the
signal
is "clean" (no
parasitics).
(3) Verify the power
output of the
rf
PA (U202):
(a)
(b)
(c)
(d)
Remove
FDS
module U203.
Connect a 50Q
probe with a
30dB
pad to
a
power
meter, and probe pin 13 (mid-band and
vhf)
or pin 10 (uhf) of
rf
PA U202. Make sure
that the probe
is
grounded (use the ground
side
of
C204
on
mid-band and vhf radios; use
a screw head
for ground on uhf
radios). Do
not touch
pin 13
(mid-band and vhf)
or pin 10
(uhf) with your finger during this
check.
Key
the radio.
Six
to
seven watts
should be
measured (high-power PA).
1.
If
the power level is incorrect,
check
the
V-
control line of (pin 3) U202. With the
FDS
module
(U203) removed,
this line should
go
to the maximum level
(6.8
to
7.0 Vdc).
Reinstall
FDS
module U203.
1.
If
the
voltage level
in
step
f
(3) (c)
1
was
low,
dekey
the radio. short pins
3
and
6 of
U202 together. This
will force the
rf
PA
into
maximum gain.
Read
the power level
again as
in
step
f
(3) (c).
(4) Verify the operation
of the
PA
control circuit
in
U201:
(a)
(b)
(c)
(5) (a)
While keying the
radio,
measure the voltage
on the
RF DETECT
line at
U203,
pin
5
(mid-
band and vhf)
or pin
4
(uhf). The voltage
should be
from
2.5
to
5Vdc.
1.
The
rf
detect
line of
U203 should change
as
the power word
is
changed. Short
pins
3 and 6 of
U202 together and verify that
this line
goes
to
approximately
4.0Vdc.
While keying
the radio, measure the D/A refer-
ence voltage
at
U201,
pin
7; this
voltage sets
the power level
of
the radio.
The reference
voltage should
be
from
2.5
to
4.5Vdc; 4.5Vdc
is the maximum setting.
1.
The reference voltage should change
when the power level word
from the field
programmer
is
changed.
If
there
is
no
change, check
pin
21
of
U200
with an
oscilloscope
and verify that this line
goes
active
when the power word is being
changed.
Verify the operation
of the
op amps
in
U201 by
applying the formula,
(V
x 2)
-
4 =
Vr.
V
= the
voltage measured
in
step
f
(4) (a); Vr
=
the
voltage
that should
have been measured
in
step
f
(4) (b).
Check
the
FDS
parameters (remote
port) by
keying
the radio and measuring the
voltage
levels
at the following pins of U203:
e
(For
mid-band and vhf radios). Pin
8 =
6Vdc;
pin 9
=
4.5Vde;
pin 12 = 6.5Vdce; pin
13 =
5.0Vdc.
e
(For
uhf radios). Pin 7
=
4.7Vde
(transmit)
and
7.4Vdc (receive);
pin 8
= OVdc;
pin
11
=
7.5Vdc.
(b)
If
any
of the
voltages measured were
incor-
rect,
check
that
U201,
pin
23,
is
set
to
remote
antenna enable
(4.6Vdc). This sets
up the
biasing
to
the diodes
in
FDS
module
U203 via
the transmit
ALC
IC, U201, pins 20, 24, 26, and
28 (vhf)
or pins 16, 17, and
20
(uhf).
g. No
Receive
/
Poor Receive
(1) Inject
53.55MHz
(mid-band and vhf)
or
73.35MHz
(uhf)
from
a frequency generator
at or
near the
antenna and listen
for the
presence
of
a
1kHz
tone.
Use
the
generator's
HI-LEVEL
output
@
0dB
(1kHz
modulation,
3kHz deviation).
If
the tone
(signal)
is
present, continue
with
this procedure;
if
no
tone is heard,
go
to
step
g
(3).
(2)
Check
the radio's
rf
section:
(a) Using a frequency counter
with
a 50Q probe,
check
the
synthesizer's
input to the
ist
LO
(U4,
pin
1
for mid-band or pin 3 for
vhf; U2,
pin
4
for uhf),
using the guide
pin of
the front
end module (mid-band and vhf)
or
the front-
end
screw head
(uhf) for ground.
The
reading
should indicate
53.55MHz
+
carrier frequency
(mid-band and vhf)
or
carrier frequency
-
73.35MHz
(uhf).
1.
If
the desired frequency cannot be read,
remove the
front end module and
check
the
input
again, using
the ground
side
of
capacitor C51 (mid-band and vhf)
or
C212
(uhf) for probe ground.
If
the desired fre-
quency
is
present, continue with this pro-
cedure (radio
in
remote):
a.
(For
uhf radios only).
The
uhf front
end module
(U2)
and the
RX
5Vdc
regulator
(U201)
will not function
if
the
FDS
module
(U203)
is not
in
place.
Turn the radio
off,
then
back
on
again,
then do the following:
(1)
If
the
FDS
module is
in
place
but
there is
still no
RX
5Vdc
at
pin 3
of U2,
check
the
voltages
on pin
7
(7.4Vdc),
pin
8
(OVdc), and
pin
11
(7.5Vdc)
of
U203
in
remote only.
(2)
Another indication would be
to
key
the radio momentarily, then
check
RX
5Vdc.
If
the
voltage
is
correct,
check Q207
and
Q208,
and/or
replace the
FDS
(U203).
b.
Check
that the
16.8MHz reference
signal
is
present at
pin
1
of
U300.
2.
If
the desired frequency is present, contin-
ue with this procedure (radio
in
remote).
(b) Using
a
5002
probe, inject the carrier frequen-
cy
at
pin 2 of
U4 (mid-band and vhf)
or pin
9
of
U203 (uhf). The signal level should
be
25
Check
for proper
drive level (250mV)
and verify that the
signal
is "clean" (no
parasitics).
(3) Verify the power
output of the
rf
PA (U202):
(a)
(b)
(c)
(d)
Remove
FDS
module U203.
Connect a 50Q
probe with a
30dB
pad to
a
power
meter, and probe pin 13 (mid-band and
vhf)
or pin 10 (uhf) of
rf
PA U202. Make sure
that the probe
is
grounded (use the ground
side
of
C204
on
mid-band and vhf radios; use
a screw head
for ground on uhf
radios). Do
not touch
pin 13
(mid-band and vhf)
or pin 10
(uhf) with your finger during this
check.
Key
the radio.
Six
to
seven watts
should be
measured (high-power PA).
1.
If
the power level is incorrect,
check
the
V-
control line of (pin 3) U202. With the
FDS
module
(U203) removed,
this line should
go
to the maximum level
(6.8
to
7.0 Vdc).
Reinstall
FDS
module U203.
1.
If
the
voltage level
in
step
f
(3) (c)
1
was
low,
dekey
the radio. short pins
3
and
6 of
U202 together. This
will force the
rf
PA
into
maximum gain.
Read
the power level
again as
in
step
f
(3) (c).
(4) Verify the operation
of the
PA
control circuit
in
U201:
(a)
(b)
(c)
(5) (a)
While keying the
radio,
measure the voltage
on the
RF DETECT
line at
U203,
pin
5
(mid-
band and vhf)
or pin
4
(uhf). The voltage
should be
from
2.5
to
5Vdc.
1.
The
rf
detect
line of
U203 should change
as
the power word
is
changed. Short
pins
3 and 6 of
U202 together and verify that
this line
goes
to
approximately
4.0Vdc.
While keying
the radio, measure the D/A refer-
ence voltage
at
U201,
pin
7; this
voltage sets
the power level
of
the radio.
The reference
voltage should
be
from
2.5
to
4.5Vdc; 4.5Vdc
is the maximum setting.
1.
The reference voltage should change
when the power level word
from the field
programmer
is
changed.
If
there
is
no
change, check
pin
21
of
U200
with an
oscilloscope
and verify that this line
goes
active
when the power word is being
changed.
Verify the operation
of the
op amps
in
U201 by
applying the formula,
(V
x 2)
-
4 =
Vr.
V
= the
voltage measured
in
step
f
(4) (a); Vr
=
the
voltage
that should
have been measured
in
step
f
(4) (b).
Check
the
FDS
parameters (remote
port) by
keying
the radio and measuring the
voltage
levels
at the following pins of U203:
e
(For
mid-band and vhf radios). Pin
8 =
6Vdc;
pin 9
=
4.5Vde;
pin 12 = 6.5Vdce; pin
13 =
5.0Vdc.
e
(For
uhf radios). Pin 7
=
4.7Vde
(transmit)
and
7.4Vdc (receive);
pin 8
= OVdc;
pin
11
=
7.5Vdc.
(b)
If
any
of the
voltages measured were
incor-
rect,
check
that
U201,
pin
23,
is
set
to
remote
antenna enable
(4.6Vdc). This sets
up the
biasing
to
the diodes
in
FDS
module
U203 via
the transmit
ALC
IC, U201, pins 20, 24, 26, and
28 (vhf)
or pins 16, 17, and
20
(uhf).
g. No
Receive
/
Poor Receive
(1) Inject
53.55MHz
(mid-band and vhf)
or
73.35MHz
(uhf)
from
a frequency generator
at or
near the
antenna and listen
for the
presence
of
a
1kHz
tone.
Use
the
generator's
HI-LEVEL
output
@
0dB
(1kHz
modulation,
3kHz deviation).
If
the tone
(signal)
is
present, continue
with
this procedure;
if
no
tone is heard,
go
to
step
g
(3).
(2)
Check
the radio's
rf
section:
(a) Using a frequency counter
with
a 50Q probe,
check
the
synthesizer's
input to the
ist
LO
(U4,
pin
1
for mid-band or pin 3 for
vhf; U2,
pin
4
for uhf),
using the guide
pin of
the front
end module (mid-band and vhf)
or
the front-
end
screw head
(uhf) for ground.
The
reading
should indicate
53.55MHz
+
carrier frequency
(mid-band and vhf)
or
carrier frequency
-
73.35MHz
(uhf).
1.
If
the desired frequency cannot be read,
remove the
front end module and
check
the
input
again, using
the ground
side
of
capacitor C51 (mid-band and vhf)
or
C212
(uhf) for probe ground.
If
the desired fre-
quency
is
present, continue with this pro-
cedure (radio
in
remote):
a.
(For
uhf radios only).
The
uhf front
end module
(U2)
and the
RX
5Vdc
regulator
(U201)
will not function
if
the
FDS
module
(U203)
is not
in
place.
Turn the radio
off,
then
back
on
again,
then do the following:
(1)
If
the
FDS
module is
in
place
but
there is
still no
RX
5Vdc
at
pin 3
of U2,
check
the
voltages
on pin
7
(7.4Vdc),
pin
8
(OVdc), and
pin
11
(7.5Vdc)
of
U203
in
remote only.
(2)
Another indication would be
to
key
the radio momentarily, then
check
RX
5Vdc.
If
the
voltage
is
correct,
check Q207
and
Q208,
and/or
replace the
FDS
(U203).
b.
Check
that the
16.8MHz reference
signal
is
present at
pin
1
of
U300.
2.
If
the desired frequency is present, contin-
ue with this procedure (radio
in
remote).
(b) Using
a
5002
probe, inject the carrier frequen-
cy
at
pin 2 of
U4 (mid-band and vhf)
or pin
9
of
U203 (uhf). The signal level should
be
25
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