Heathkit IT-12, Инструкция по сборке

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INTRODUCTION
The Heathkit Visual-Aural Signal Tracer is a compact, service-designed instrument incorporating many features that
meet the everyday needs of the service technician. Some of the features and applications are listed below:

High gain position for direct signal tracing in RF or IF circuits.

High gain position for signal tracing in audio circuits.

Convenient RF or audio switch in probe body.

Tracer may be used for AM, FM, and TV circuit exploration.

Visual signal indicator.

Noise locator circuit.

Utility amplifier for checking record changers, tuners, etc.

Useful for checking microphones, musical instruments, pick-ups, and speakers.

Substitution speaker and output transformer.

Output level indicator.
CIRCUIT DESCRIPTION
The Heathkit Signal Tracer is a transformer operated, quality instrument, consisting primarily of a high-gain audio
amplifier. A built-in 3-1/2" speaker is provided for sound and an electron ray tube permits visual observation of the
output level. Additional features are RF and audio inputs in one convenient probe, noise locator circuit, and substitution
speaker, and output transformer.
Observing the schematic it can be seen that the RF-audio switch S2, mounted directly in the shielded probe body,
switches condenser C1 and a crystal diode in or out of the circuit for RF or audio applications. Condenser C1 isolates the
crystal diode to prevent any voltage damage.
The Noise Switch S3, connects B+ to the probe lead through resistor R14 to provide the noise locator circuit. The switch
S2 in the probe must be in the audio position for this function.
Signals from the probe are coupler, through condenser C2 to the gain-control R1 and in turn through condenser C3 to the
input grid of VI. Condenser C2 and C3 prevent noisy operation of the gain-control.
The tube VI, 12AX7, is a high-gain dual triode with the plate of section A coupled through con-denser C4 to the grid of
section B.
The condenser C5 couples VI (B), to the grid of V2, 12 CA5 beam power output tube. The primary of the output
transformer is center tapped and all three primary leads are brought out to terminals on the front panel. The power switch
S1-B in the off position disconnects the B+ so the trans-former may be used as a substitute output transformer.
The secondary leads are connected to the speaker voice coil panel terminals, and one side may be disconnected with the
speaker switch S4 when the speaker is used as a substitute.
Resistor R9 and condenser C6 couple a small amount of the output signal to the grid of V3, 1629 eye tube.
The Signal Tracer is transformer operated, and uses a silicon diode in a half-wave rectifier circuit. The transformer also
supplies 12.6 volts AC for the tube filaments.