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3-15
J.6.
POWER
AMPLIFIER; RF--UNIT
12
(PM 5390
S),
fig.
47
The
instrument
version
PM
5390
S
supplies increased
output
level
up
to
+13 dBm,
corresponding
lo
an output
voltage of
1
Vrms
into
50
^2.
There
does not
exist
any
conversion
kit
to
change
PM
5390
into
PM
5390
S.
The
20 dB
power
amplifier has
two
signal
paths:
During
output
level
settings
between -127
dBm
and -17
dBm
(software version I-A.1/I1-A.1
)
the power
amplifier
is
supplied
by -12
V, Instruments
including
software
1-9.
1/11-9.1
between -127
dBm
-27 dBm.
In this
case pin-diodes
402,
404
have low
resistance,
while pin-diodes
401,
403
have
resistance.
The
RF
signal
passes
to
amplifier
304,
where
insertion
loss
of
2
dB
is
compensated.
Frequen-
cy
response
is
adjusted
by
C517
and R620.
If
output
levels
>
-17
dBm
(software
1-9.1/11-9.1
>
-27
dBm)
are selected
the
power
amplifieMS
supplied
by +24
V.
The
signal
path
is
switched over
and
the
RF
is
fed to the
20
dB
amplifier
stage
comprising
amplifiers
301,
302
and 303.
The
frequency response
of
this signal
path
is
adjusted
by
C520
and R622,
see table 7.3.1
,
final
adjustments.
For
soldering of
replacement
components
use
only
resin-core
solder
tin
with
silver.
3.7.
POWER
SUPPLY; UNIT
10 (motherboard)
Sevon
supply
voltages are
generated
by
the supply
section of unit 10:
Two
stabilized
+5
V
voltages are
generated
by
regulators
354/355,
+5A
for
the
digital
part
of the
units
1,
2,
3,
10 and
+5B
for
the keyboard/display
interface, units
4
and
5.
The
display unit
is
separately
supplied
in
order to have
less
influence
by
scan
interference.
+12A
is
a stabilized
voltage
realized
by
the
four-terminal voltage regulator
351;
it
supplies
RF
units
1
and
2.
Ground
connections
are
conducted
separately
to
U10
to
have
less
interference/hum and
should
not
be
altered.
Special
effort
is
made
for
the supply voltage of the loop
filter in
the
PLL
circuitry:
a
+35
V
stabilized
supply
voltage
is
generated
by
precision regulator
302 on
unit
7.
This
voltage
is
applied
via
coaxial cable
to
RF-unit
2,
where
additional
filtering
and
hum
suppression
is
achieved.
Overmore
this
voltage
is
applied
to precision
regulator
323 on
RF—
U2
to
generate
+27
V
supply
voltage for
the loop
filter
315.
Two
regulators,
352, 353,
generate three supply voltages,+12
B and -12 A/-12
B, for units 2,
3 and
10.
Some
other
stabilized
voltages are
generated
directly
on
the
units
where
they
are
needed:
~
regulator
322,
RF-U2,
generates
+5
V,
regulator
321,
RF-U2,
supplies
ECL
voltage
for
the
prescaler
—
regulator
307,
RF-U1
,
generates
+5
V.
Furthermore
control voltages to switch the
RF
units
1
and 2
are realized
by
8
reed
relais
801-808
and
inverter
356.
+24
V
supply
voltage
and
reed relay
810
are
present only
in
the
PM
5390
S
version to
supply
and
switch
the
20 dB power
amplifier.
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