FREQUENCY STANDARD ADJUSTMENT

TM 11-5820-918-13

5-15. FREQUENCY STANDARD ADJUSTMENT. Over long periods of time, the tem-

perature-controlled quartz crystal in the frequency standard will show effects of pre-

cession (frequency change due to crystal aging). When the rate of precession in the

receiver and transmitters is not equal, the effects of a difference will show up by ver-

tical movement of a received path on the RCS-4B receiver CRT. Normally a path can

be recentered on the receiver CRT by means of the receiver SLIP control. If the SLIP

control is adjusted to recenter any single path more than once in eight hours, there

is need to adjust the frequency standard on the transmitter. However, if all trans-

mitter displays show drift on the CRT in the same direction, it is necessary to adjust

the receiver frequency standard. (Refer to RCS-4B receiver manual. )

5-16. To make the transmitter frequency adjustment, the direction of drift on the

RCS-4B receiver CRT must be determined. If the displayed path is moving downward,

the 1024 front panel fine control (STD ADJ) should be turned counterclockwise. If

the displayed path is moving upward, the control should be turned clockwise. (One

full turn of the control changes the drift rate by approximately 0.5 milliseconds per

24 hours.) If the front panel control range is insufficient (total range is 20 turns

end to end) to make the correction, it should be recentered, and the adjustment made

on the coarse control located on the 1024 frequency standard 1A3 (figure 5-1).

Adjust the coarse frequency control by turning it in directions opposite to that of

the front panel fine adjust. If the display is drifting downward, turn the coarse

adjustment clockwise. One turn of the coarse frequency adjustment will compensate

for a drift of 100% of CRT height per 24 hours (5ms/24hrs) for a 2-30 MHz sweep,

or 50% of CRT height for 2-16 MHz sweeps.

5-17. 5018 POWER SUPPLY ADJUSMENT (S/N 400101 and on). Variations in input

line voltage can be accommodated by adjusting the positions of taps on the transformer

primary. The adjustment is made on assembly 2A2 (figure FO-23) by unsoldering the

standard 115/230 volt connections at pins 4 and 9 of T1 and moving higher or lower

in voltage as required. With voltages less than 110 or 215 VAC , move connections on

respective primaries to pins 3 and 8. With voltages greater than 120 or 250 VAC, move

connections to pins 5 and 10.

5-18. 4011 POWER SUPPLY ADJUSTMENTS . The 4011 power supply provides DC volt-

ages of +5, +6, +26, -240, -270 VDC. None of the voltages requires adjustment; how-

ever, they; should be periodically checked in accordance with the performing verifi-

cation test (paragraph 5-29). Adjustment to accommodate low AC input voltages can

5-19. AC INPUT ADJUSTMENT. Lower voltage variations from the standard 115 or 230

VAC input can be accommodated by changing connections to the line voltage switch.

Upper limits of 120 or 240 VAC can be tolerated using the same factory wiring as for

115/230 volt. If the line voltage is closer to the alternative 105 or 220 volt, remove

the AC switch bracket on assembly 3A2A1 ( schematic figure FO-29) and remove

existing gray and white wires from pins 1 and 3 respectively on the underside of the

switch. Replace the 230 volt gray wire with the 220 volt gray/white wire (sorted from

the transformer cable) and replace the 115 volt white wire with the 105 white/black

wire. Insulate the exposed ends of the unused wires and secure wires to the cable

bundle.