SAFETY, CARE, AND HANDLING.

TM 11-5820-401-34-3/0967-LP-432-3060

DIFFERENCES BETWEEN MODELS/SILICON VERSIONS. (CONT)

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IF Amplifiers A4200(*) and Audio/Squelch Preamp A4300(*)

The A4200A uses an integrated circuit quadrature-type fm demodulator in place of the Travis-type dis-

criminator used in the A4200. Therefore, only one coil (L4202) requires peaking, and no dc offset

voltage is present at TP4003. Since the A4200A demodulator's output is only 53 millivolts minimum

compared to 100 millivolts minimum for the germanium version, readjustment of the Squelch Pre-

amplifier A4300(*) is necessary when an A4200A is used to replace an A4200.

Squelch Amplifier A5200(*) and Squelch Filter A5300(*)

The silicon versions of these two modules differ from the germanium versions in operating levels and

ac feedback. An integrated circuit dual differential amplifier is used as a squelch amplifier, tone

detector, and voltage comparator.

A separate relay driver circuit is provided to operate K5002, eliminating this relay's effect on squelch

adjustment with temperature changes and age.

The amplifier gain between TP5012 and TP5008 is minimal, but independent of the frequency setting of

A5300A. Therefore, offsetting the squelch filter to achieve the required gain is not required.

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SAFETY, CARE, AND HANDLING.

WARNING

High voltage is used in this equipment. Death on contact may result if safety precautions

are not observed.

Remove all rings, watches and jewelry before turning power on.

Make certain you are not grounded when working inside the equipment with power turned

on. Do not attempt internal service or adjustment unless another person is present who

is capable of rendering first aid and resuscitation. A periodic review of safety precau-

tions in TB 385-4, Safety Precautions for Maintenance of Electrical/Electronic

Equipment, is recommended.

Fumes of TRICHLOROTRIFLUOROETHAN E are poisonous. Provide adequate ventilation

whenever you use TRICHLOROTRIFLUOROETHAN E. Do not use solvent near heat or open

flame. TRICHLOROTRIFLUOROETHAN E will not burn, but heat changes the gas into

poisonous, irritating fumes. DO NOT breathe the fumes or vapors. TRICHLOROTRl-

FLUOROETHANE dissolves natural skin oils. DO NOT get the solvent on your skin. Use

gloves, sleeves, and an apron which the solvent cannot penetrate. If the solvent is taken

internally, consult a physician immediately.

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