POWER AMPLIFIER A2A1 ALIGNMENT

TM 11-5820-919-40-2

POWER AMPLIFIER A2A1 ALIGNMENT

The alignment procedure is to be used in either of these situations: (1) the performance test calls a potentiometer out of adjustment, or (2) one of the following is

replaced:

Overshoot Control AR3, AR4

ALC, AR3

Buffers ART, AR2

Power Transistors Q3, Q6, Q10, Q11

Transformers T1, T2, T3, T4, T5

DC-DC Converter

The procedure consists of a preliminary setup and an adjustment procedure.

R1 = GAIN ADJUST

PRELIMINARY SETUP

ADJUSTMENTS

R13 = BIAS ADJUST

R24 = +30.5 VDC ADJUST

1. Remove the power amplifier from the amplifier/coupler.

1. Monitor TP-3 with DVM, close PTT. On bottom board adjust R24

R34 = ALC REFERENCE

Connect the test setup as shown in figure 9-3, however, to

for +30.5 + 0.5 vdc. Open PTT.

ADJUST

not connect the of coax cable at this time. The of coax cable

connected at A1J2 will be connected directly to the coaxial

2. On the 18 pin extender cable remove the jumper lead between

attenuator.

the two test points. Insert a dc ammeter in place of the jumper and

select a range of at least 100ma. Ensure that positive lead is

2. Set dc power supply (7 amp) to +24.5 vdc. Set step

inserted into test point closest to the connector on the PA module.

attenuator to 10 db.

Close PTT only long enough to adjust R13 (top board) for a reading

of 90ma.

3. Set ANT SEL to 50 ohm (bypass), VOLUME to on.

FREQUENCY KHZ to 29, 999.1, SB to USB, MODE TO

3. Adjust the rf signal generator to 29.9999 MBz at +22 dbm (150

V-TR.

mw). Refer to Note 7 on figure 9-3. Connect the rf coax cable to

A1J1 and the rf signal generator. Adjust R1, GAIN ADJUST

(topboard), for a reading of 27 mw on the power meter.

4. With DVM, monitor E8. Close PTT, adjust R34 (bottom board) for

a reading of +13.5 + 0.5 vdc.

5. Open PTT, disconnect test equipment.