1024 POWER SUPPLY ADJUSTMENTS (S/N 400100 and before)

TM 11-5820-918-13

h. Adjust the 1024 frequency standard coarse adjust potentiometer in the fre-

quency standard module (1A3) until the waveform on scope channel 2 appears to stand

still or drift very slowly relative to channel 1. The coarse adjust potentiometer is

accessible through a small hole in the frequency standard module cover.

i. An acceptable drift rate is no more than one cycle of the 1024 5 MHz waveform

drifting off the scope screen every 30 seconds, assuming the scope time base is set

to 0.1 us/division. The direction of drift (right or left) does not matter.

j. Wait 30 minutes and repeat steps h and i. Fine adjustment to correct minor

drift may be made with the 1024 front panel STD ADJ potentiometer.

k. Wait 30 minutes and verify that drift rate remains acceptable. Make fine ad-

justment if necessary.

1. Replace 1024 top cover. Calibration is complete.

5-36. 1024 POWER SUPPLY ADJUSTMENTS (S/N 400100 and before). The 1024 has

two power supply adjustments. One is to adjust the +5 volt standby power supply

for the timing circuits and is designated +5V B. The other adjustment is for the AC

input power in the event that the available line voltage is lower than the acceptable

limits for nominal 115 or 230 VAC input.

WARNING

Use extreme care when making internal adjustments with power on.

Potentially lethal voltages are present in the transmitter.

5-37. +5V B REGULATION. Measurement of the +5V B power is accomplished at the +5V

B test point on the transmit logic module 1A2 (figure 5- 10). If adjustment of the +5V

B supply is necessary, perform the following steps:

a. Remove four screws securing the frequency standard 1A3 to the chassis plate

of the 1024.

b. Turn the assembly upside down to allow access to the +5V switching regulator

1A3A3.

c . Adjust +5V B at R7 on assembly 1A3A3 (figure FO-35).

5-38. AC INPUT ADJUSTMENT. This adjustment involves connection of a low-line tap

to compensate for line voltage variations that are below acceptable limits. The 1024

operates satisfactorily when the main line input is between 110 and 125 volts (for 115V

position of line voltage select toggle switch) or 215 to 250 volts (for 230V position).

Use of the low-line tap (220 - 105) is only necessary if line voltages lower than 110V

(or 215V) are expected. To make this adjustment,disconnect wire at TB1, pin 1 that

goes to switch S1 (power), and connect wire to TB1, pin 2 (figure FO-34).

5-39. 5018 POWER SUPPLY ADJUSTMENT (S/N 400100 and before). The 5018 has

six power supply adjustments, five controls to adjust the +27.1 volt regulators sup-

plying the driver amplifier and individual power amplifier modules, and one for con-

trolling main line AC deviations from the nominal 115 or 230 VAC standard.