8-44F: Equipment Faults 1

Question 1

8-44F2

Range rings on the PPI indicator are oval in shape. Which circuit would you suspect is faulty?

A. Timing circuit.
B. Video amplifier circuit.
C. Range marker circuit.
D. Sweep generation circuit.

Answer 1

ANSWER D
If the range rings on the scope are more oval than round, you are going to need to make a slight adjustment to the sweep generation circuit to bring the rings back into a round shape. This is a yearly calibration process that should be checked every time you are inside the RADAR lower unit.

Question 2

8-44F3

What would be the most likely defective area when there is no target video in the center of the CRT and the blank spot gets smaller in diameter as your range scale is increased?
A. The TR (TRL) Cell.
B. The local oscillator is misadjusted.
C. Video amplifier circuit.
D. The lF amplifier circuit.

Answer 2

ANSWER A
If you still have a blank spot in the middle of the tube, you might suspect misadjustement of the internal TR cell timing circuitry. If not properly timed, the TR cell desensitizes the receiver; this affects close-in echoes most.

Question 3

8-44F5

In a RADAR using digital video processing, a bright, wide ring appears at a fixed distance from the center of the display on all digital ranges. The transmitter is operating normally. What receiver circuit would you suspect is causing the problem?

A. VRM circuit.
B. Video storage RAM or shift register.
C. Range ring generator.
D. EBL circuit.

Answer 3

ANSWER B
In diagnosing this symptom of a wide ring that appears on all digital ranges at the same distance from the center of the display, you should suspect a problem in the video random access memory (VRAM). It should generate proper range rings that change in proportion to the radar range you select.