Repair or Replacement

(6) Increase the speed slowly to 8000 rpm and

(b) If hipot equipment is available, test the

turn the pile screw slowly. The regulated voltage

coil insulation to the spool at 600 volts for one

will at first rise and then drop slightly. Set the pile

second.

screw approximately in the position shown in figure

e. Repair or Replacement. With the exception of

3-5. The coil current (at no-load, 8000 rpm) should

cleaning pitted or blackened surfaces as described

be about 0.65 ampere. If the current is high, turn

in d (1) and (5), defective parts cannot be repaired

the magnet core in. Tighten the locking screws

and must be replaced.

uniformly. If the current is low, loosen magnet

f. Reassembly. The regulator can be reassembled

locking screw and turn magnet body out.

by reversing the disassembly procedures being

careful to make connections in accordance with

( 7 ) Allow the regulator to come up to

figure 3-3. Observe special instructions described

operating temperature by operating at 3500 rpm

for ten minutes.

below:

(1) If the magnet core has been removed,

(8) A pair of earphones connected as shown in

screw it up until 10 mils under flush, measuring

figure 3-4 can be used to check the stability of the

regulator. A stable regulator produces a humming

from the raised rim on the hole of the magnet plate

noise or steady roar. A rapid series of popping

and stop (46, fig. 3-2).

noises indicates instability. Listen carefully at high

(2) When replacing the armature in the

housing, the terminal on the armature should be

speeds when shocking (applying and removing full

load) the regulator to detect instability. An

near the upper left tapped hole.

oscilloscope may also be used to check stability.

(3) Insert the magnet plate with chamfered

outer edge in.

When using an oscilloscope, instability is indicated

by low frequency, high-amplitude discontinuous

(4) The magnet assembly should be securely in

place before inserting the carbon pile.

oscillations, usually off scale on the screen. Do not

confuse with the higher frequency commutator

(5) When inserting the carbon pile hold the

regulator with the glass tube in a vertical position to

ripple.

minimize carbon breakage. While in this position

(9) The exact position of the pile screw should

the pile screw should be turned in to apply slight

be obtained by checking the full load and no-load

pressure to the pile.

regulated voltage at 8000 rpm. The full load

(6) Replace parts should be sprayed or

voltage should not vary more than plus or minus

brushed with a moisture or fungus-resistant,

0.1 volt from the no-load voltage. The coil current

varnish (Military Specification MIL-V-173A, Type

must be between 0.645 and 0.655 ampere. At 3500

I, or equivalent). Do not apply varnish to terminal

rpm, the full-load voltage should not be more than

boards, resistors, or rheostats.

0.5 volt lower than the no-load voltage. Adjust the

g. Test Procedure. It is preferable to use the same

magnet body as described in g (6). Recheck the

type of generator that the regulator will be used

pile screw setting and coil current until both voltage

with in service. The rpm values in the text below

and current requirements are satisfied.

refer to a generator with a speed range of 3000-

(10) Record the no-load voltages at 3 5 0 0 ,

4500, 6000, and 8000 rpm, also read voltage at

8000 rpm. These values will be different for other

ratings.

10,000 rpm, no-load, without shocking. The

regulated voltage should remain between 27.5 volts

(1) Mount the regulator on the test stand and

make connections shown in figure 3-4.

and 28.3 volts for all readings. If the voltage does

not remain between these limits, turn the pile screw

(2) The regulator should be wired in ac-

in slightly and recheck para g(9).

cordance with figure 3-3.

(3) Resistance values for checking the coil

(11) Increase the speed from 3500 to 8000

rpm without shocking and record the voltage at

windings, resistors and rheostat are given in d (11).

(4) Set the rheostat at its midposition. Make

8000 rpm. Shock several times at 8000 rpm and

sure that the magnet locking screws are tight.

note the voltage. The difference between the two

readings should not be greater than 0.3 volt. If it is

(5) Turn the pile screw out (counterclockwise)

until pressure on the carbons is relieved. Do not

greater, replace the carbon disks and check the

back out pile screw too far as end carbons may

insulation tube for cleanliness and cracks.

become dislocated and will break when the pile

(12) With the regulator operating, close the

equalizer switch and adjust the voltage drop across

screw is turned in (clockwise). Start the generator

the equalizer coil at the regulator terminals to 0.25

and note the voltage. It should be less than 10 volts.

If it is not, the carbon pile is too long and one

volt. Make sure the polarity is as shown on figure 3-

4. Read the voltage with the switch open at 5500

washer should be removed. The voltage should

rpm (no-load). Close the switch and again read the

start to rise when the pile screw is turned in (clock-

voltage. The voltage should drop between 2.25 and

wise).

3-2