Heathkit IM-4180 - Page 22

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Integrated circuit U108 functions as an adjustable
voltage regulator. DC voltage from the power source
is coupled into U108 pins 2 and 3. The regulated
racictonr R122 to
provide overload current limiting. 8V Adj control
R186 sets the 8-volt level for the IC and transistor
circuits.
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If the Battery Charger/Eliminator Accessory pack is
used, resistor R181 limits current flow tothe batteries.
Switch SW102 is used in the Charge position when
rechargeable batteries are used, and in the No Charge
position for all other Charger and battery applica-
tions.
TUNED CIRCUIT AND RESONATOR
Coiltan tan LI + anoanan
COli Liu an
f a 200 kHzresonant
circuit. IF eal nad IC U101 supplies the resonant
circuit through resistor R116. The resultant resonant
circuit voltage feeds detector nioce D106. During
calibr atnr V1n4 acl 4
calibration, resonator Yiu is coupled into a positive
feedback path and causes the IF amplifier and
preamplifier to oscillate at 200 kHz.