Sensitivity Adjustment

TM 11-6660-204-25

proximately 10 seconds and note the deviation from

rim with the left hand; with the right hand, hold out

the retainer spring that is found on the cover's rim.

the 40 division ordinate.

Turn the cover counterclockwise and lift it at the

(3) Momentarily depress the REC TEST switch

same time.

to cause the pen to move upscale 10 to 40 recorder

c. Rotate the contact arm of the slide-wire to its

divisions and then move back downscale. Again al-

maximum counterclockwise position as viewed from

low the pen to record the value for approximately 10

seconds and note the deviation as before.

above (fig. 3-6).

d. Manually position the pen carriage so that the

(4) Check the deviation of the values recorded in

(2) and (3) above. Adjust the SENSITIVITY control

pen is positioned at a point between one-third and

me-half of a chart division to the left of the chart zero

to cause this deviation to be minimum.

inc.

(5) Repeat the above procedures until three or

e. Tighten the left-hand screw that secures the

more traces on each side of the 40 recorder division

drive cable to the pen carriage.

ordinate are obtained with a maximum deviation of

0.2 recorder division.

f. Manually rotate the contact arm of the slide-

wire to its maximum clockwise limit.

(6) Turn the REF ADJUST control to reposition

g. The pen should record just to the left of the

the pen to 30 recorder divisions.

b. Alternate Procedure.

extrusions at the righthand end of the chart drive

(1) With the SIGNAL SELECTOR set at 60

roller. If the pen contacts these extrusions, it may be

CPS, turn SENSITIVITY control R213 (fig. 2-21)

damaged. If necessary, readjust the pen downscale

clockwise until the pen carriage jitters back and

slightly as described in c, d, and e above.

forth.

h. Tighten the right-hand screw that secures the

(2) Slowly turn the control counterclockwise un-

drive cable to the pen carriage.

i. Turn on the equipment and allow it to warm up

til the jitter of the pen just disappears. Look through

the window and observe the pinion gear on the bal-

for 10 minutes.

j. Perform the sensitivity adjustment (para 3-34).

ancing motor shaft; it will still have a noticeable

Disregard any deviation in balance positions of the

small jitter. This point is the best compromise be-

pen.

tween the level of sensitivity that causes pen jitter

k. Turn the SIGNAL SELECTOR switch to the

and the level that makes the pen too sluggish in its

S.C. position.

response to error voltages.

(3) Try the servo response on the three fixed-

l. Turn the REC ZERO control to its midpoint

signal positions of the SIGNAL SELECTOR switch

screwdriver slot vertical).

(S. C., 60 CPS, and 120 CPS). If the pen movement is

m. Loosen the two mounting screws on the slide-

jerky the sensitivity may be backed off a little more

wire plastic molding. (One of these screws also se-

cures a cable clamp.) Loosen the screw holding a

3-35. Pen Lifter Adjustment

second clamp near the cable clamp.

Turn the PEN LIFTER potentiometer R215 to its

n. Carefully rotate the loosened slide-wire until the

counterclockwise limit. Then slowly advance it

pen records at the chart zero line to within one-tenth

again, while alternating the SIGNAL SELECTOR

of a chart division.

switch between 60 C.P.S. and 120 C.P.S. positions

o. Tighten the mounting screws on the slide-wire

Advancing this potentiometer will shorten the tail on

molding.

p. Adjust the REC ZERO control to bring the re-

the recorder signal; this tail should be between one

and two chart divisions in length. Adjust the potenti-

corder pen exactly on the chart zero line.

ometer to get that result.

q. Replace the slide-wire cover.

NOTE

3-34. Sensitivity Adjustment

Occasionally a recorder may not provide

a. Preferred Procedure.

proper pen lifter operation with the nor-

(1) With the SIGNAL SELECTOR switch in the

mal sensitivity setting. Increase, or de-

60 C.P.S. position, turn the REF ADJUST control to

crease the sensitivity as needed for satis-

cause the pen to be positioned to 40 recorder divi-

factory pen lifter operation.

sions. Allow the pen to record this value for approxi-

3-36. Recorder Test Adjustment

mately 10 seconds.

(2) Momentarily depress the INTER

Depress REC TEST switch S204. The pen should

SCOUTER SC switch to cause the pen to move

record at 95 recorder divisions. If it does not, adjust

down-scale 10 to 40 divisions and then move back

REC TEST ADJ potentiometer R211 while holding

upscale. Allow the pen to record this value for ap-

the REC TEST switch depressed, until the pen does

Change 3

3-24