User Manual

G3S-800-140-031 Installation & Service Manual

044-05095 Rev. A 6-3 September 2001

If an amplifier is in DC FAIL and the LPA Disable LED is illuminate, then one of the four amplifier

DC voltages is either out of tolerance or not present. Return the amplifier to the factory for repair.

6-2.6 FAN FAIL Illuminated

If an amplifier is in FAN FAIL, then the one of the amplifier’s cooling fans has failed. Replace the

fan.

Fan failure does not cause the amplifier to shut down; amplifier shut down is determined by heat

sink temperature.

6-2.7 LOOP FAIL Illuminated

9. Loop Fail is always accompanied by LPA Disable LED illuminated. This may be due to

A. Inability of the amplifier to maintain a 180° phase shift between the first and second

loops.

B. A damaged error amplifier. This can be caused by

1. Out of band spurious or intermods being applied at too high of a level at the ampli-

fier input port. An input band-pass filter may be necessary to correct this problem.

2. Disconnecting amplifier RF output cables while the amplifier is still turned on. Al-

ways turn the amplifier off when moving output RF cables from the hatch plate to

test equipment and back again.

C. Improper power balance between amplifiers in a given subrack.

1. Ensure the amplifier thumbscrews are properly tightened. Reset the amplifier by

momentarily pressing the Reset button on the amplifier front panel up.

2. Try seating the amplifier in another subrack slot.

3. Try seating the amplifier in a subrack in another sector.

6-2.8 LOW PWR Illuminated

Low Power is always accompanied by the LPA Disable LED illuminated. This is due to the gain of

either the internal preamplifier or main amplifier being 0.5 dB (typically) or more below the ampli-

fier specification. The amplifier should be returned to the factory.

6-2.9 LPA DISABLE Illuminated

10. LPA Disable LED illuminated indicates that the amplifier RF section is turned off. This may

be due to

A. An accompanied alarm indicating a critical amplifier fault (i.e. Loop Fail fault).

B. A response to a subrack command, purposely inhibiting the amplifier (i.e. Sleep Mode

activation)

C. Improper seating of the amplifier in the subrack.

11. Ensure the amplifier thumbscrews are properly tightened. Reset the amplifier by momentar-

ily pressing the Reset button on the amplifier front panel up.

12. Try seating the amplifier in another subrack slot.

13. Try seating the amplifier in a subrack in another sector.

6-3 Return For Service Procedures