is a starting value. It will be re-adjusted during test for minimum
intermods and FM noise.
•
Connect a 30dB, 20W attenuator to the output of the amplifier.
•
Apply B+ to both supply connections of the amplifier module.
•
Apply a low level sweep to the module and measure the gain (be sure to
take into account the 30dB pad). Gain should be about 21dB to 24dB.
VOLTAGE REGULATOR BOARD
CIRCUIT DESCRIPTION
The Voltage Regulator board comprises two identical regulator circuits. One is
described below; the description for the second is the same except for the component
numbers.
The voltage regulated is based on a monolithic regulator IC MC1723CP and a
pass transistor for current handling capability. The regulator IC compares a sample of the
output voltage to an on-chip reference. The sample is applied to pin 4 through a resistive
divider consisting of R7, R9 and R11. Varying R7 changes this sample thus changing the
output voltage. The output of the IC (pin 10) drives the PNP transistor U2 through a
Darlington transistor Q3.
Short circuit protection is provided by Q1 and Q4. Q4 shunts the drive away from
the base of U2 when the output current causes the voltage across R6 and R10 to rise high
enough to open transistor Q1. Supply voltage for the IC is via R8 and CR3 from the 30V
supply.
Metering outputs are provided for the supply as well as those for current drawn
from each regulator and the total current from the 30V supply. The voltage metering
outputs have calibration pots whereas the current metering outputs are preset with fixed
resistors.
Set up Procedures
•
Set up one power supply for 65V; current limited to 1A and another
supply for approximately 30V, also current limited to 1A.
•
Apply the voltages to the appropriate inputs, 65V to E1 and E13; 30V
to E12.
•
Adjust R7 for a voltage of 50V at E4. Adjust R24 for 50V at E16.
•
Check for 30V output at E11 (the same as that applied to E12).
•
Reset the 65V supply current limit to approximately 7A, and apply
sufficient load (to draw approximately 5A at 50V) to E4 and to E16
alternately, to check the regulation of the supply. The output at either
one should not drop more than 1V under load.
