Adjustment of Regulated Power Supplies

TM 11-6660-204-25

3-29. Adjustment of Regulated Power Supplies

This pressure should be 2 ounces; it is varied by

adjustment of the tension of the pen pressure spring

a. Positive Regulated Power Supply. This unit is

(fig. 2-21).

adjusted to give a constant output potential of 300

c. Adjustment to Eliminate Erratic Pen Opera-

volts under normal loads. Connect the positive lead

tion. Erratic operation of the pen may be caused by

of a voltmeter (300-500 volt range) to J404 and the

any one or a combination of the following conditions:

negative lead to chassis. Adjust R412 for a reading of

(1) A loose connection between the drive cable

300 volts.

and the pen carriage. Check visually and/or check the

b. Negative Regulated Power Supply. This unit is

alignment of the pen against the position of the arm

adjusted to give a constant output potential of 175

of the slide and trolley wire (para 3-33).

volts under normal load. Connect the negative lead of

(2) Slackness in the drive cable. If this condition

a voltmeter (300-500 volt range) to J413 and the

exists, increase the tension by turning the setscrew

positive lead to chassis. Adjust R434 for a reading of

on the drive cable guide pulley located on the right

175.

side of the recorder. Turn the setscrew until the

3-30. Noise Suppression Diode Alignment

spring is completely compressed, and then back it off

1 full turn.

Noise suppression diode alignment is a direct sup

(3) A worn condition of the traveling trolley con-

port maintenance procedure and requires the use of

tacts. If either one of these is worn half through,

an oscilloscope. However, if a replacement unit is not

replace both of them. Pressure on the new contacts

immediately available, or the situation is such that

should be adjusted to between 1.75 and 2.5 ounces.

equipment cannot be removed from operation for

To adjust the pressure, bend the contact spring as

direct support maintenance, the following procedure

required for a course adjustment. To make the fine

will temporarily provide noise suppression of a noisy

adjustment, loosen, the two screws that hold the

radiosonde signal:

contact arm and slide the arm toward or away from

a. Set the noise suppression switch S301 fig.

the contacts, as indicated. While performing these

3-15), to the IN position.

adjustments, turn the small backup screw on the side

b. Use a pencil to mark the position of the slots of

of the contact arm out of the way; after the adjust-

potentiometers R304 and R306.

ment is completed, turn the screw in as far as it will

c. Listen to the speaker and observe the pen. Ad

go and tighten the locknut. Check to see that there is

just potentiometer R306 (fig. 3-15) to the maximum

a minimum of 1/16inch clearance between any part

of turns in each direction and listen to the speaker

of either contact spring and the slide. Also be sure

for a reduction in noise while still maintaining a

that there is adequate clearance between the heads of

steady pen trace.

the screws that hold the contact assembly to the

d. Adjust potentiometer R304 a maximum of

contact arm and the bottom part of the slide-wire

turn in either direction for a reduction in noise while

housing. Rotate the contact arm throughout its en-

still maintaining a steady pen trace.

tire excursion in making this clearance check.

e. If noise cannot be adjusted out by this method

return both potentiometers (R304 and R306) to their

original (as marked) positions.

3-22

Change 3