Model 75A250A
Manual Text
2-1
REV A
SECTION II
OPERATING INSTRUCTIONS
2.1
G
ENERAL
Operation of the Model 75A250A broadband RF amplifier is simple. The amplifier’s input signal, whether
swept or fixed in frequency, is fed into the jack labeled
INPUT,
and the amplifier’s output signal is taken
from the jack labeled
RF OUTPUT.
The unit is turned on by activating the
POWER
switch. A circuit
breaker in the AC power line provides protection in the event of a unit malfunction. A polarized, three-
wire AC power cord is also included with the unit to provide cabinet and chassis grounding to the power
mains.
C
AUTION
:
O
PERATION OF THE
M
ODEL
75A250A
BROADBAND
RF
AMPLIFIER IS NOT CRITICAL IN REGARD TO
SOURCE AND LOAD
V
OLTAGE
S
TANDING
-W
AVE
R
ATIO
(VSWR),
AND IT WILL REMAIN
UNCONDITIONALLY STABLE UNDER ANY MAGNITUDE AND PHASE CONDITIONS OF SOURCE AND LO AD
.
I
T HAS ALSO BEEN DESIGNED TO WITHSTAND INPUT POWER LEVELS UP TO TWENTY
(20)
TIMES ITS
RATED INPUT OF
1
M
W
WITHOUT SUSTAINING DAMAGE
. H
OWEVER
,
SIGNAL LEVELS
>>
20
M
W
OR
TRANSIENTS WITH HIGH PEAK VOLTAGES CAN DAMAGE THE AMPLIFIER
. A
LSO
,
ACCIDENTAL
CONNECTION OF THE AMPLIFIER
’
S OUTPUT TO ITS INPUT CAN CAUSE OSCILLATIONS THAT WILL
PERMANENTLY DAMAGE ITS INPUT CIRCUITRY
.
N
OTE
:
A
LTHOUGH THE
M
ODEL
75A250A
HAS BEEN DESIGNED FOR THE OVERDRIVE AND LOAD TOLERANCE
CONDITIONS DESCRIBED ABOVE
,
SUBJECTING THE AMPLIFIER TO THESE CONDITIONS
SIMULTANEOUSLY CAN CAUSE FAILURE OF THE UNIT
’
S OUTPUT TRANSISTORS
.
REPEATED FAILURES OF
THIS NATURE WILL NOT BE COVERED UNDER THE UNIT
’
S WARRANTY
.
The Model 75A250A Amplifier is protected from input overdrive by a diode limiter on the RF input.
The Model 75A250A power transistors are protected from over-temperature by a sensor that senses the
heat sink temperature near the RF output transistors. In the event of a cooling fan failure or an air flow
blockage, the DC voltage will be removed from the RF stages; if and when the heat sink temperature
reaches approximately 70°C, the unit’s front panel vacuum fluorescent display (VFD) will read
THERMAL FAULT
. Normal operation can be resumed by resetting the Model 75A250A after the heat
sink temperature drops below 70°C.
Содержание 75A250A
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