U.S. Divers Impulse Operating instructions

Impulse
SecondStageRegulator
P.O. Box 25018 ●3323 W. Warner Ave. ●Santa Ana, CA ●92799-5018
Copyright ©1997 U.S. Divers Co., Inc. Doc. No. 1078-56
Authorized
Aqua-Lung™ Dealer
SERVICE & REPAIR MANUAL

TableofContents
Introduction .................................................................................................... 1
Warnings, Cautions, & Notes ........................................................................................... 1
Scheduled Service ........................................................................................................... 1
General Guidelines ........................................................................................................... 1
Initial Inspection Procedure .......................................................................... 2
External Inspection ........................................................................................................... 2
Pressure Test .................................................................................................................... 2
Disassembly Procedures............................................................................... 3
Reassembly Procedures................................................................................ 6
Final Adjustment & Testing Procedures..................................................... 10
Second Stage Air Flow Test............................................................................................ 12
Second Stage Opening Effort Test ................................................................................. 12
Second Stage Purge Flow Test ...................................................................................... 12
External Leak Test .......................................................................................................... 12
Subjective Breathing Test ............................................................................................... 13
Table 1 - Troubleshooting Guide ................................................................. 14
Table 2 - Recommended Tool List ............................................................... 15
Table 3 - Standard Parts Replacement Schedule ...................................... 15
Table 4 - Torque Specifications ................................................................... 16
Table 5 - Test Bench Specifications ............................................................ 16
Procedure A - Cleaning & Lubrication ....................................................... 17
Table A - Recommended Lubricants & Cleaners ...................................... 18

Service&RepairManual-ImpulseSecondStage
Doc. #1078-56
Introduction
This manual provides factory prescribed proce-
dures for the correct service and repair of the Im-
pulse second stage. It is not intended to be used as
an instructional manual for untrained personnel. The
procedures outlined within this manual are to be
performed only by personnel who have received
factory authorized training through a U.S. Divers®/
Aqua-Lung®Service & Repair Seminar.
If you do not completely understand all of the
procedures outlined in this manual, contact U.S.
Divers Co., Inc. to speak directly with a Technical
Advisor before proceeding any further.
Warnings, Cautions, & Notes
Pay special attention to information provided in
warnings, cautions, and notes that are accompanied
by one of these symbols:
A WARNING indicates a procedure or situation
that may result in serious injury or death if
instructions are not followed correctly.
A CAUTION indicates any situation or tech-
nique that will result in potential damage to the
product, or render the product unsafe if in-
structions are not followed correctly.
A NOTE is used to emphasize important
points, tips, and reminders.
Scheduled Service
Because the Impulse regulator, complete with a
first stage, is considered to be a life-supporting
product, it is extremely critical that it receives ser-
vice according to the procedures outlined in this
manual on a regularly scheduled basis; at least once
a year with normal or infrequent use.
NOTE: A unit that receives heavy or frequent
use, such as in rental, instruction, or commer-
cial applications, should be serviced at least
twice each year - or more often - depending on
the conditions of use and the manner in which
it is maintained. (Refer to the care and mainte-
nance procedures outlined in the Impulse
Owner’s Manual.)
GENERAL GUIDELINES
1. In order to correctly perform the procedures
outlined in this manual, it is important to follow
each step exactly in the order given. Read over
the entire manual to become familiar with all
procedures before attempting to disassemble the
Impulse, and to learn which specialty tools and
replacement parts will be required. Keep the
manual open beside you for reference while
performing each procedure. Do not rely on
memory.
2. All service and repair should be carried out in a
work area specifically set up and equipped for
the task. Adequate lighting, cleanliness, and
easy access to all required tools are essential for
an efficient repair facility.
3. Before beginning any disassembly, it is impor-
tant to first perform the Initial Inspection proce-
dure, and refer to Table 1 - Troubleshooting to
determine the possible cause of any symptoms
which may be present.
4. As each regulator is disassembled, reusable
components should be segregated and not
allowed to intermix with non-reusable parts or
parts from other regulators. Delicate parts,
including inlet fittings and crowns which contain
critical sealing surfaces, must be protected and
isolated from other parts to prevent damage
during the cleaning procedure.
5. Use only genuine factory parts purchased di-
rectly from U.S. Divers (or an authorized dis-
tributor outside of the U.S.) when servicing any
U.S. Divers/ Aqua-Lung product. Substitution
with another manufacturer’s parts constitutes an
after-market modification of the product, and
renders all warranties null and void.
6. Do not attempt to reuse mandatory replacement
parts under any circumstances, regardless of the
amount of use the product has received since it
was manufactured or last serviced.
7. Do not overtighten parts beyond their torque
specification when reassembling. Most parts are
made of either marine brass or plastic, and can
be permanently damaged by undue stress.

2Impulse Second Stage Service & Repair Manual
© 1997 U.S. Divers Co., Inc.
Initial Inspection Procedure
EXTERNAL INSPECTION
1. Visually inspect the first stage filter to check for any signs that
contaminants, such as moisture, rust, aluminum oxide, or
charcoal may have entered the IP hose and second stage.
NOTE: An orange, rust colored residue on the filter usually
indicates that the regulator has been used with a corroded
steel cylinder. Gray or white discoloration may indicate use
with a corroded aluminum cylinder. Advise the customer of
this, and the possible need to obtain service for their cylin-
der. A green discoloration positively indicates that moisture
has entered the regulator, and internal corrosion is therefore
likely to be found.
2. Slide back the hose protectors to inspect the condition of the
IP hose at its fittings and along its length. Check closely for
any signs of deterioration or damage, including blistering and
abrasion, and corrosion of the fittings.
3. Inspect the condition of the mouthpiece to check for torn bite
tabs, holes, or deterioration.
PRESSURE TEST
1. Prior to performing any disassembly, ensure that the second
stage is connected to a first stage with a stable intermediate
pressure of 140 psi (±5), with no open ports or hoses.
2. Connect the first stage to a cylinder that is filled with 3,000
psi, and open the cylinder valve to pressurize the regulator.
3. Turn the second stage adjustment knob completely out
counter-clockwise. A slight leak of airflow should be present.
4. Slowly turn the adjustment knob clockwise, noting the mea-
sure of turns required to stop the airflow. Airflow should stop
between 1/2 to 3/4 turn.
5. Turn the adjustment knob completely in clockwise, and listen
closely to check for any signs of leakage from the second
stage. If necessary, immerse the second stage in water to
locate the source of any leakage found and refer to Table 1 -
Troubleshooting to determine its possible cause.
CAUTION: If the second stage freeflows uncontrollably,
immediately shut the cylinder valve and proceed directly to
the Disassembly Procedure. Do not attempt to further
inspect the regulator while pressurized.
6. Depress the purge button to determine whether sufficient
airflow is provided to clear the second stage of water. Imme-
diately after releasing the purge button, listen closely to ensure
that the second stage does not continue to flow any air.
7. Turn the cylinder valve shut and depress the second stage
purge button to depressurize the regulator before proceeding
to the following Disassembly Procedure.

Impulse Second Stage Service & Repair Manual 3
© 1997 U.S. Divers Co., Inc.
Disassembly Procedures
NOTE: Before performing any disassembly, refer to the
schematic drawing, which references all mandatory replace-
ment parts. These parts should be replaced with new, and
must not be reused under any circumstances - regardless of
the age of the regulator or how much use it has received
since it was last serviced.
CAUTION: Use only a plastic or brass O-ring removal tool
(P/N 9440-22) when removing O-rings to prevent damage to
the sealing surface. Even a small scratch across an O-ring
sealing surface could result in leakage. Once an O-ring
sealing surface has been damaged, the part must be re-
placed with new. DO NOT use a dental pick, or any other
steel instrument.
1. Slide back the hose protector(10) to expose the IP hose fitting.
2. While holding the hex nut(11) of the second stage secure with
a 22mm open end wrench, apply a 11/16"open-end wrench
to the female fitting of the IP hose(8). Turn the fitting counter-
clockwise to loosen and remove the hose from the second
stage. Remove the O-rings(7&9) from the hose and discard.
Set the hose aside.
3. Carefully snip the plastic mouthpiece clamp(16) and remove
the mouthpiece(15) from the box bottom. Inspect the mouth-
piece to ensure it is free of any tears or cuts that may cause
leakage of water into the second stage or other discomfort.
Discard or set the mouthpiece aside to be reused, depending
on its condition.
4. While holding the second stage secure, gently twist the
boxtop(1) 45°counter-clockwise to disengage from the box
bottom(6). (See Fig. 1.) Pull the boxtop straight away from
the box bottom to remove, and press out the purge cover(2).
5. Securely mate both pins of the Circlip/ Retaining Ring Tool
(P/N 1078-46) into two opposite holes of the retaining ring(3).
While applying even downward pressure to prevent slippage
of the tool, carefully turn the retaining ring counter-clockwise
to loosen and remove.
6. Lift out the thrust washer(4) and diaphragm(5). Closely
inspect the diaphragm to ensure that it is perfectly round and
free of any tears, deterioration, or other damage. If deteriora-
tion or damage is found, discard the diaphragm and do not
attempt to reuse.
7. Apply a 22mm open end wrench to the hex nut, and turn
counter-clockwise to loosen and remove from the inlet end of
the valve body(23).
8. Turn the adjustment knob(32) completely out counter-clock-
wise until it stops. This will hold the retaining pin(24) in
place when the valve module is removed from the box bottom.
9. While holding the box bottom secure and the lever(26) com-
Fig. 1 - Boxtop Removal

4Impulse Second Stage Service & Repair Manual
© 1997 U.S. Divers Co., Inc.
pletely depressed with one hand, firmly grasp the adjustment
knob and pull straight out to remove the entire valve module
assembly from the box bottom (see Fig. 2).
CAUTION: Do not attempt to remove the valve module
assembly from the box bottom without first holding the lever
depressed. Doing so may cause serious damage to the box
bottom, lever, or poppet, which will require their replacement.
10. Remove and discard the O-ring(22a), which will be either on
the inlet end of the valve body, or loose inside the box bottom.
11. Remove the spacer bushing(12) from the inlet opening of the
box bottom, and examine to ensure that it is perfectly round in
its center and shows no signs of damage or deterioration. If
damage or deterioration is found, discard and do not reuse.
12. While holding the valve module secure and horizontal with
the lever facing up, turn the adjustment knob slightly clock-
wise to allow the retaining pin to fall out. Set the pin aside.
NOTE: If the retaining pin does not easily fall out of the
valve body after the adjustment knob has been turned slight
clockwise, it may be necessary to press it out, using the pin
of the Seat Extraction Tool (P/N 1094-36).
13. Continue to hold the valve module secure, and turn the adjust-
ment knob counter-clockwise until it has disengaged from the
threads of the valve body. Remove and inspect the washer(29)
for any signs of wear or damage, and discard if found.
14. Remove and discard both O-rings(30&31), and set the adjust-
ment knob aside to be cleaned separately in a mild acid bath
(white vinegar), outside of an ultrasonic cleaner.
15. Remove the O-ring(22b) from the valve body and discard.
16. Stand the valve body vertical with the inlet end facing up, so
that the lever hangs down. Gently spread the arms of the lever
evenly apart until the poppet/ LP seat assembly(27) disen-
gages and falls out inside the valve body (see Fig. 3). Relax
the arms of the lever, and lift the valve body straight up to
allow the poppet/ LP seat assembly and spring to fall out.
Remove the spring from the poppet, and set both items aside.
17. While holding one arm of the lever pressed securely against
the side of the valve body, gently pull the other arm out of the
opposite side with thumb and forefinger (see Fig. 4). When it
has disengaged from the valve body, pull the other arm out
and set the lever on a flat surface with the tips facing down.
18. Before performing any further disassembly, closely inspect the
shape of the lever to determine whether it is distorted, cor-
roded, or otherwise damaged. While laying on a flat surface
with the tips facing down, all four tips should rest evenly on
the same plane, without being cocked or bent upward (see Fig.
5). If damage or corrosion is found, discard the lever and do
not attempt to bend it to its original shape or otherwise reuse.
19. Closely examine the poppet spring with a magnifier to ensure
Fig. 2 - Valve Module Removal
Fig. 4 - Removing Lever
Fig. 3 - Disengaging Poppet From Lever

Impulse Second Stage Service & Repair Manual 5
© 1997 U.S. Divers Co., Inc.
it is not damaged (bent) or corroded. If any signs of damage
or corrosion are found, discard the spring and do not reuse.
20. Discard the poppet/ LP seat assembly, and do not attempt to
reuse, regardless of its condition.
21. While holding the valve body secure, press against both ends
of the deflector clip(25) with thumb and forefinger to remove,
and set it aside.
22. While holding the valve body secure, apply a medium blade
screwdriver to the slotted head of the adjustable crown(21),
and turn the crown counter-clockwise to disengage its threads.
NOTE: Because the crown is O-ring sealed, it will not freely
exit the valve body after it has been unthreaded. The follow-
ing step must be performed correctly in order to remove the
crown without damaging its delicate sealing surface.
23. When the crown has been unthreaded from the valve body,
carefully insert the pin of the Seat Extraction Tool through the
opposite end of the valve body and through the opening in the
center of the crown. Gently press the crown out (see Fig. 6).
Remove and discard the O-ring(20).
24. Closely examine the crown with the use of magnifier, check-
ing for any scoring, nicks, or other damage to the polished
sealing surface. If damage is found, discard the crown, and do
not attempt to reuse. If it is in reusable condition, set it aside
on a soft surface to prevent damage to the sealing edge.
25. Using a blunt probe, turn the circlip(18) which retains the
vane adjustment switch(14) as needed to ensure that the open
ends face towards the outlet boss. Place the box bottom down
on a flat, padded surface, so that the outlet boss and exhaust
tee face up.
26. While holding the box bottom secure, place the tines of the
Circlip/ Retaining Ring Tool (P/N 1078-46) squarely against
the ends of the circlip (see Fig. 7). Gently press the circlip
straight off the vane adjustment switch, and set it aside.
27. Pull the vane adjustment switch straight up and out of the
outlet boss of the box bottom. Remove and discard the O-
ring(13), and set the switch aside.
28. While holding the box bottom secure, remove the exhaust tee
by firmly pulling one side off and then the other.
CAUTION: Do not use a tool to remove the exhaust tee.
Doing so may cause serious damage to the seating flange,
requiring replacement of the box bottom.
29. Remove the exhaust valve diaphragm(9) from the box bottom
and discard.
This concludes the disassembly of the Impulse second
stage. Refer directly to Procedure A and Table A, titled
Cleaning & Lubrication, before proceeding to the Reas-
sembly Procedures.
Fig. 7 - V.A.S. Circlip Removal
Fig. 6 - Crown Removal
Fig. 5 - Lever Inspection

6Impulse Second Stage Service & Repair Manual
© 1997 U.S. Divers Co., Inc.
Reassembly Procedures
NOTE: Before performing any reassembly, it is important to
inspect all parts, both new and those that are being reused,
to ensure that every part and component is perfectly clean
and free of any dust, corrosion, or blemishes. Before dress-
ing each O-ring with silicone grease, check to ensure that it
is clean, supple, and free of any blemish.
WARNING: Use only genuine U.S. Divers parts, subassem-
blies, and components whenever assembling U.S. Divers
products. DO NOT attempt to substitute a U.S. Divers part
with another manufacturer’s, regardless of any similarity in
shape, size, or appearance. Doing so may render the
product unsafe, and could result in serious injury or death.
1. Install the O-ring(13) onto the vane adjustment switch(14).
2. Mate the stem of the vane switch into its respective hole in the
box bottom(6), above the outlet boss, and align the mating pin
above the positioning guide (see Fig. 8). When the switch is
correctly aligned, press it down and into place so that it is
properly seated inside the box bottom.
3. Press the circlip(18) into the recessed ledge in the forks of the
Circlip/ Retaining Ring Tool (P/N 1078-46), with its flat side
facing down and the open end facing out of the tool (see Fig.
9). The spring tension of the tool will hold the circlip in place
while it is being positioned inside the box bottom.
4. While holding the vane switch in place, set the box bottom on
a flat surface with the open side facing down and the switch at
12 o’clock. Guide the tool holding the circlip into the outlet
boss, with the top surface of the tool held flush against the
inner wall directly behind the vane. Press the circlip evenly
onto the groove of the vane stem until it snaps audibly into
place (see Fig. 10). Remove the tool and examine closely to
ensure that the circlip is seated completely inside the groove.
Remove and reinstall the circlip if necessary.
CAUTION: It is important to ensure that the vane adjust-
ment switch, O-ring, and circlip are correctly installed in
order to maintain the watertight integrity of the box bottom
assembly. Improper installation may result in flooding of the
second stage.
5. Install the exhaust valve diaphragm(19) into the box bottom
by gently pulling the stem through the hole in the center of the
support spokes, until the barb has passed through and is
securely seated against the opposite side. Carefully snip off
the excess material of the stem with a small pair of scissors.
6. Install the exhaust tee(17) onto the box bottom by fitting it
over one upper corner of the seating flange and then stretching
it over the other. Firmly press the lower portion of the tee
onto the flange until it is completely seated.
Fig. 9 - Loading Circlip Tool
Fig. 8 - V.A.S. Alignment
Flat Side Facing Down
Fig. 10 - V.A.S. Circlip Installation
Fig. 11 - Lever & Valve Body Alignment
Positioning
Mark

Impulse Second Stage Service & Repair Manual 7
© 1997 U.S. Divers Co., Inc.
CAUTION: Do not use a tool to install the exhaust tee.
Doing so may cause serious damage to the seating flange,
requiring replacement of the box bottom.
7. Lay the valve body(23) lengthwise with the positioning mark
facing up as shown in Figure 11. Gently flex the arms of the
lever(26) evenly apart while fitting them over the positioning
mark and onto the valve body, until they are seated inside their
respective square holes. Closely examine the shape of the
lever to ensure that it has not become bent during installation.
8. Install the O-ring(20) onto the crown(21), and carefully insert
the threaded end of the crown into the inlet end of the valve
body. Gently press it in further with the blunt end of the seat
extraction Tool (P/N 1094-36) until it stops (see Fig. 12).
9. Apply a medium blade screwdriver to the slotted head of the
adjustable crown, and turn the crown clockwise to engage the
threads. Continue turning the crown clockwise to the full
extent of its thread engagement, and stop turning when resis-
tance is felt. Then turn the crown out counterclockwise
exactly 2 1/2 turns to arrive at its correct preliminary setting.
10. Closely inspect the poppet/ LP seat assembly(27) to ensure
that the low pressure seat is seated securely inside the head of
the poppet, and that no foreign matter, indentations, or scars
are visible. Fit the spring(28) over the stem of the poppet
assembly, so that it is seated securely at the base.
11. Stand the valve body vertically with the male threaded inlet
end facing down, and positioned so that the lever faces di-
rectly to the left, resting perpendicular to the valve body.
While holding the poppet assembly by the spring, align the
poppet above the top of the valve body so that the two retain-
ing ears which engage the arms of the lever are facing directly
to the right; opposite of the lever (see Fig. 13).
12. Lower the poppet assembly and spring straight down inside
the barrel of the valve body without disturbing this alignment,
so that the poppet assembly is resting directly over the arms of
the lever. Gently spread both arms of the lever evenly outward
to allow the poppet assembly to drop into place, and relax the
lever arms (see Fig. 14).
WARNING: DO NOT attempt to press the poppet forcefully
into the barrel of the valve body, past the arms of the lever.
Doing so may damage the poppet and impair its correct
engagement with the lever. If left undetected, this damage
could lead to serious injury or death.
13. Turn the valve body over to ensure that the poppet does not
fall out, and test the movement of the lever to the ensure that it
swings freely as the valve body is turned over in each direc-
tion, without any interference. If the poppet assembly falls
out of the valve body, or if the lever does not swing freely
back and forth, remove the poppet and closely inspect the
retaining ears for any signs of damage, such as cracking or
Fig. 12 - Crown Installation
Fig. 14 - Poppet & Lever Engagement
Fig. 13 - Poppet & Lever Alignment
"Ears"

8Impulse Second Stage Service & Repair Manual
© 1997 U.S. Divers Co., Inc.
breakage. If damage is found, discard the poppet and replace
with new before repeating steps 11-12.
14. Install the O-ring(22b) into the groove of the valve body that
is adjacent to the hexagonal feature.
15. Install the larger O-ring(31) into the groove in the base of the
shaft on the adjustment knob assembly(32), being careful to
avoid rolling the O-ring down over the threads. Install the
smaller O-ring(30) into the groove near the top of the shaft.
16. Place the anti-friction washer(29) over the nub of the adjust-
ment knob shaft, and carefully mate the adjustment knob shaft
into the large open end of the valve body. While maintaining
inward pressure against the poppet spring, turn the adjustment
knob clockwise to engage the threads. Check to ensure that
the lever rises immediately as the adjustment knob assembly is
mated into the valve body.
17. Continue turning the adjustment knob clockwise to the full
extent of its thread engagement until it stops, and then turn it
back out 1/2 turn counter-clockwise.
18. While holding the valve assembly horizontally so that the
lever faces down, insert the retaining pin(24) into the hole that
is adjacent to the O-ring. Ensure that the pin drops into place
inside the hole without protruding out, and screw the adjust-
ment knob completely in clockwise until it stops. This will
hold the pin securely in place to prevent it from falling out
while installing the valve module into the box bottom.
19. Lay the valve module assembly horizontally so that the adjust-
ment knob faces to the right and the lever is on its side, facing
furthest away. Closely examine the deflector clip(25) to locate
the dimpled feature which will mate into the hole that is facing
up in the center of the valve body barrel. Position the clip
over the hole so that the longer leg above the dimple faces
towards the lever, and the shorter leg faces away (see Fig. 15).
Press the clip into place so that the dimpled protrusion mates
into the hole, and inspect the outlet port on the opposite side
to ensure that it is open and unobstructed by the deflector clip.
CAUTION: The deflector clip must be correctly installed to
ensure proper airflow and performance of the second stage
valve. If installed upside-down or on the opposite side of the
valve body, the deflector clip will obstruct the outlet port and
severely limit the flow of air from the second stage.
20. Orient the box bottom with the open face facing up. While
holding the lever depressed, pass the inlet end of the valve
module through the opening in the right side of the box bot-
tom until the lever can stand up freely inside.
CAUTION: Be careful not to loosen the adjustment knob
while installing the valve module into the box bottom. It is
very important to keep the knob turned completely in clock-
wise, in order to hold the retaining pin in place.
Fig. 15 - Deflector Clip Alignment
Short Leg

Impulse Second Stage Service & Repair Manual 9
© 1997 U.S. Divers Co., Inc.
21. Turn the valve module as needed to align the hex feature with
the hexagonal opening of the box bottom so that the lever
stands straight up inside. Press the valve module completely
into the box bottom, until the adjustment knob is flush against
the outer side.
22. Place the O-ring(22a) over the threaded inlet of the valve
body, so that it rests inside the opening of the box bottom.
23. Place the hexagonal spacer bushing(12) over the threaded inlet
of the valve body, and align it with the hexagonal opening of
the box bottom. Press the bushing completely down over the
valve body to seat the O-ring beneath it.
24. Thread the hex nut(11) clockwise by hand onto the inlet of the
valve body, with the flat side facing in towards the box bottom
and the shoulder facing out. While holding the box bottom
secure, apply a torque wrench with 22mm crow-foot to tighten
the hex nut snug to a torque measurement of 45-55 inch-lb.’s.
25. Turn the adjustment knob out counter-clockwise only until
resistance is felt; to ensure that the knob cannot be completely
unscrewed and removed from the valve body. This will
positively determine whether the retaining pin has been
correctly installed and will effectively hold the adjustment
knob securely in place.
WARNING: If the adjustment knob can be completely
unscrewed and removed from the valve body, do not attempt
to assemble any further. Disassemble as needed to cor-
rectly install the retaining pin. Severe injury or death may
otherwise result from attempting to use the second stage if
the retaining pin is not correctly installed.
26. Install the diaphragm(5) into the box bottom with its raised
center facing up, and check to ensure it is evenly seated onto
the shoulder at the base of the threads.
27. Install the thrust washer(4) over the diaphragm, and tamp
down to ensure that it seated evenly on all sides.
28. Place the retaining ring inside the open face of the box bottom
with the side that contains four open holes facing up. Without
disturbing the position of the diaphragm or thrust washer, turn
the retaining ring clockwise to engage the threads, and apply
the Circlip/ Retaining Ring Tool to tighten completely snug.
29. Check the secure fit of the diaphragm by grasping the raised
portion of the diaphragm between thumb and forefinger, and
gently moving the diaphragm back and forth, up and down. If
the diaphragm is not securely fastened in place, disassemble
as needed to reinstall the diaphragm, thrust washer, and
retaining ring before performing any further assembly.
30. Fit the purge cover(2) inside the box top(1), and align the box
top over the open face of the box bottom so that the extended
portion is facing 45 degrees below (counter-clockwise to) the
inlet of the second stage (see Fig. 16a). After achieving the
Fig. 16a - Boxtop Installation - Step 1

10 Impulse Second Stage Service & Repair Manual
© 1997 U.S. Divers Co., Inc.
correct alignment, press the box top evenly onto the box
bottom and turn 45 degrees clockwise, until the extended
portion is centered directly over the inlet (see Fig. 16b).
31. Install the mouthpiece(15) onto the box bottom, and lightly
fasten a clamp(16) onto the groove of the mouthpiece. Turn
the clamp so that the locking tab is facing toward the inlet side
of the box bottom, and pull the clamp sufficiently snug. Snip
the extra length with a small pair of scissors or wire cutters.
This concludes the reassembly of the Impulse second
stage. Refer directly to the following section, titled Final
Adjustment & Testing.
Final Adjustment & Testing Procedures
NOTE: Before performing the following procedure, refer to
Table 5, titled Test Bench Specifications - Impulse 2nd Stage
CAUTION: Prior to adjusting and testing the Impulse sec-
ond stage regulator, the accompanying first stage must be
correctly serviced, adjusted to a stable intermediate pressure
of 140 psi , and fully tested. Refer to either the Conshelf SE
Service Manual (P/N 7802-08) or the SEA Service Manual
(P/N 7802-12) before attempting to perform the adjustment
and testing of the Impulse second stage.
1. Thread the male fitting of the IP hose into the preferred low
pressure port of the first stage, and apply a torque wrench with
11/16" crow-foot to tighten to 40 inch-pounds (±2).
2. Connect an intermediate pressure test gauge (P/N 1116-10) to
the first stage via a separate low pressure hose.
3. Attach the female fitting of the second stage low pressure hose
to the In-Line Adjustment Tool (P/N 1001-95) by mating the
swivel nut onto the male threaded end of the tool. Turn the
swivel nut clockwise until finger snug (see Fig. 17).
4. Pull back the knob of the tool to retract the adjusting stem,
and mate the female threaded end of the tool onto the second
stage inlet fitting. While holding the tool secure, turn the
second-stage clockwise until lightly snug.
5. Turn the second stage adjustment knob completely out
counter-clockwise, and set the vane adjustment switch to the
"MIN" position (see Fig. 18).
6. Connect the first stage to a filtered air source of 3,000 psi.
NOTE: The preferred air source for final tuning and testing is
a flow bench with accurately calibrated gauges. If a flow
bench is not available, a scuba cylinder may be used, follow-
ing the subjective breathing test provided on page 13.
7. Slowly open the valve of the air supply to fully pressurize the
regulator. Press the knob of the inline adjustment tool inward,
Fig. 17 - In-Line Adjustment Tool Connection
Fig. 18 - Preliminary Settings
Fig. 16a - Boxtop Installation - Step 2

Impulse Second Stage Service & Repair Manual 11
© 1997 U.S. Divers Co., Inc.
and gently turn the knob until it can be felt that the adjustment
stem has mated into the slotted head of the crown. Continue
to hold the knob inward, in order to prevent it from being
pressed outward by the internal air pressure.
a. If airflow cannot be heard, slowly turn the crown out
counter-clockwise only until a very slight leak is present.
b. If strong airflow beyond a slight leak is present, slowly turn
the crown clockwise in very small increments of adjust-
ment while simultaneously depressing the purge of the
second stage, and pause to listen after each adjustment until
only a slight leak remains. It is important to adjust the
crown in this manner only until the airflow has stopped,
without over-adjusting. When only a slight amount of
airflow is present, release the knob of the adjustment tool to
ensure that it no longer makes contact with the crown.
8. When a slight leak has been established, turn the second stage
adjustment knob between 1/2 - 3/4 turn clockwise. Purge the
second stage, and then listen closely to determine whether any
airflow can still be heard.
a. If airflow can still be heard, re-engage the inline adjustment
tool with the crown as described in step 7, and turn the
crown slightly in clockwise only until the airflow has
stopped. Release the knob of the adjustment tool to ensure
that it no longer makes contact with the crown.
CAUTION: Over-adjustment of the crown will cause exces-
sive spring load in the second stage valve, and will severely
degrade the performance of the regulator.
9. To test the setting of the crown, turn the second stage adjust-
ment knob completely out counter-clockwise to initiate a
slight flow of air, and then slowly turn it back in clockwise to
verify that the airflow has stopped completely before it has
been turned 2turn. If more than 1/2 turn is required to shut
off the airflow, it will be necessary to readjust the crown as
described in step 8a.
10. After turning the adjustment knob 1/2 turn clockwise to stop
the airflow, purge the second-stage regulator several times and
listen for any leaks. Perform any follow-up adjustments as
needed at the source to eliminate the leakage.
NOTE: If leakage persists after performing the above proce-
dures, refer to Table 1, Troubleshooting, and disassemble as
required to remedy the problem.
11. Turn the valve of the air source completely shut, and purge the
second stage to depressurize the system. Disconnect the in-
line adjustment tool from the second stage, and connect the
female fitting of the IP hose to the second stage inlet. Apply a
torque wrench with 11/16" crow-foot to tighten the IP hose
fitting to a torque measurement of 40 inch-lbs (±3).
12. Slide the hose protector(10) over the inlet connection of the IP
hose, and mate the index tab into the box top.

12 Impulse Second Stage Service & Repair Manual
© 1997 U.S. Divers Co., Inc.
NOTE: If an accurately calibrated airflow test bench is not
available, proceed to Subjective Tuning Procedures provided
on the following page.
SECOND STAGE AIR FLOW TEST
1. With the regulator still connected to the test bench, pressurize
the system to 3000 psi (±100) and place the second-stage
mouthpiece over the mouthpiece adapter.
2. Turn the second stage adjustment knob in clockwise between
1/2 - 3/4 turn, only until the airflow has stopped.
3. Slowly turn the flowmeter control knob until the flow reaches
a minimum of 15 SCFM (425 liters per minute). The reading
on the Magnahelic gauge (inhalation / exhalation effort gauge)
should indicate no more than +6.O” H2O. If the reading
exceeds +6.0" H2O, refer to refer to Table 1 - Troubleshooting
for corrective guidelines and specific procedures.
SECOND STAGE OPENING EFFORT TEST
1. With the second stage adjustment knob turned in clockwise
1/2 - 3/4 turn, turn the flowmeter control knob shut, and then
slowly reopen while watching both the Magnahelic gauge and
the intermediate pressure gauge.
2. When the intermediate pressure gauge begins to drop below
the intermediate pressure “lockup,” the magnahelic gauge
should indicate an opening effort of +.6" of H2O to 1.0" of
H2O.
3. Turn the second stage adjustment knob completely in clock-
wise, and repeat the above procedure to ensure that the open-
ing effort does not exceed 2.7" of H2O. If the opening effort is
not within these prescribed ranges, refer to Table 1 - Trouble-
shooting.
SECOND STAGE PURGE FLOW TEST
1. Turn off the flowmeter control knob.
2. While the second-stage is still mounted on the mouthpiece
adapter, watch the flowmeter gauge and fully depress the
purge cover. The flowmeter gauge must indicate a minimum
of +5.0 SCFM (142 L.P.M.). If the purge flow is less than
+5.0 SCFM, refer to Table 1 - Troubleshooting.
3. When purge flow is correct, remove the second-stage from the
mouthpiece adapter on the flow test bench. Shut the valve of
the test bench, and purge the second stage to depressurize the
system. Remove the regulator.
EXTERNAL LEAK TEST
1. After disconnecting the regulator from the flow bench, con-
nect to a scuba cylinder filled to approximately 3,000 psi.
Open the cylinder valve to repressurize the regulator, and
submerge the entire system in a test tank of clean water.

Impulse Second Stage Service & Repair Manual 13
© 1997 U.S. Divers Co., Inc.
2. Observe any bubbles arising from the submerged regulator
over a one minute period. The recommended time is necessary
due to slower bubble formation that occurs in smaller leaks.
Bubbles indicate a leak, which requires that the system must
be disassembled at the source to check sealing surfaces, assem-
bly sequence and component positioning in order to correct the
problem(s).
NOTE: Extremely small leaks may be better detected by
applying a soap solution or Snoop™ to the leak area. Bubble
streams will indicate the source of the leak. Before disas-
sembling to correct any leaks, rinse the entire regulator
thoroughly with fresh water and blow out all residual moisture
with filtered, low-pressure (50 psi) air. Disassemble and
remedy the problem, referring to Table 1 - Troubleshooting.
SUBJECTIVE BREATHING TEST
1. While the regulator is connected to a cylinder containing 3,000
psi and pressurized, turn the second stage adjustment knob
completely out counterclockwise to the full positive position,
and verify that a slight leak of airflow is present.
2. Slowly turn the adjustment knob in clockwise to verify that the
airflow stops between 1/2 - 3/4 turn.
3. Turn the adjustment knob completely in clockwise to the full
negative position, and depress the second stage purge to ensure
that an adequate volume of air needed to clear the second stage
flows through the mouthpiece..
4. Turn the adjustment knob back to 1/2 - 3/4 turn negative, and
breathe from the second stage. A properly serviced and ad-
justed regulator should deliver air upon deep inhalation with-
out excessive inhalation effort, freeflow, or “fluttering” of the
second-stage diaphragm. When exhaling, there should be no
fluttering or sticking of the exhalation valve. If any of these
problems occur, refer to Table 1 - Troubleshooting.
This concludes annual service procedures for the Impulse

14 Impulse Second Stage Service & Repair Manual
© 1997 U.S. Divers Co., Inc.
Table1
TroubleshootingGuide
ImpulseSecond-Stage
SYMPTOM POSSIBLE CAUSE TREATMENT
NOTE: Test with second stage
adjustment knob turned in
clockwise between 1/2 - 3/4 turn
CAUTION: Recommended treatments which require disassembly of the regulator
must be performed during a complete overhaul, according to the prescribed proce-
dures for scheduled, annual service. Do not attempt to perform partial service.
Leakage or freeflow from 1. High first-stage intermediate pressure. 1. Refer to first-stage Troubleshoot-
second stage (should be 140 ±5 psi) ing Guide.
2. LP seat(27) damaged or worn. 2. Replace Poppet/ LP seat Assy.
3. Crown(21) incorrectly adjusted, 3. Reset crown and perform Final
lever(26) set too high. Tuning & Testing procedures.
4. Crown(21) sealing surface damaged. 4. Replace crown.
5. Poppet spring(28) damaged. 5. Replace poppet spring.
Low purge or excessive work 1. Low intermediate pressure. 1. Refer to first-stage Troubleshoot-
of breathing (full cylinder) (should be 140 ±5 psi) ing Guide.
2. Lever(26) not properly engaged with 2. Disassemble and inspect condi
Poppet/ LP Seat Assy(27). tion of Poppet/ LP Seat Assy.
3. Crown(21) incorrectly adjusted, 3. Reset crown and perform Final
lever(26) set too low. Tuning & Testing procedures.
4. Intermediate pressure hose(8) 4. Clean or replace hose.
clogged or obstructed.
5. Deflector clip(25) installed incorrectly. 5. Remove clip and reinstall.
External air leakage 1. Intermediate pressure hose loose. 1. Tighten to 40 inch-lbs at female
(Immersion Test) second-stage fitting.
2. Crown O-ring(20) damaged. 2. Disassemble and replace O-ring.
3. Box bottom(6) damaged. 3. Disassemble and replace box
bottom.
Water entering second-stage 1. Hole in mouthpiece(16). 1. Replace mouthpiece.
2. Demand diaphragm(5) damaged. 2. Replace demand diaphragm.
3. Exhaust diaphragm(19) damaged. 3. Replace exhaust diaphragm(s).
4. Vane Adjustment Switch O-ring(13) 4. Disassemble and replace O-ring.
dirty, damaged, or worn.
5. Diaphragm improperly seated 5. Disassemble and properly re-
between box bottom(6) and assemble. (Check for distortion.)
purge cover(2).
6. Box bottom(6) damaged. 6. Disassemble and replace box
(Check exhaust valve sealing surface.) bottom.
7. Valve body O-ring(22) damaged. 7. Disassemble and replace O-ring.
8. Spacer bushing(12) worn or damaged. 8. Disassemble and replace spacer
bushing.

Impulse Second Stage Service & Repair Manual 15
© 1997 U.S. Divers Co., Inc.
PART NO. DESCRIPTION APPLICATION
7803-00 Aqua-Lung Service Manual All Aqua-Lung regulators
1116-00 I.P. test gauge Intermediate pressure testing
N/A 0-120 inch-lbs torque wrench Small fittings
9440-22 O-ring tools O-ring removal & installation
N/A Magnifier w/ illumination Sealing surface inspection
N/A Ultrasonic cleaner Brass & stainless steel parts cleaning
N/A Medium blade screwdriver Crown removal/ installation
N/A 22mm wrench & crow foot Hex nut removal/ installation
N/A 11/16" wrench & crow foot IP hose fitting
1078-46 Circlip & Retaining Ring Tool C-clip & retaining ring removal/ installation
1094-36 Seat extraction/installation tool Crown removal & installation
1001-95 In-line adjustment tool Final adjustment & tuning
Table2
RecommendedToolList
Table3
StandardPartsReplacementSchedule
PART NUMBER DESCRIPTION KEY NUMBER QTY
9570-25 O-ring 7 1
8200-10 O-ring 9, 13, 20 3
1078-22 Exhaust Valve 19 1
1078-06 O-ring 22 1
1078-12 Poppet/ LP Seat Assy 27 1
1078-13 Washer 29 1
1078-14 O-ring 30 1
1078-16 O-ring 31 1

16 Impulse Second Stage Service & Repair Manual
© 1997 U.S. Divers Co., Inc.
Table4
TorqueSpecifications
PART NUMBER DESCRIPTION / KEY NUMBER TORQUE
1005-35 LP Hose Female Fitting / 8 40 (±3) inch-lbs
1078-03 Hex Nut / 11 50 (±5) inch-lbs
Table5
TestBenchSpecifications
TEST CONDITION ACCEPTABLE RANGE
Leak test Inlet 2,500-3,000 (±100) psi
Knob turned full out CCW Slight leak
Knob turned in CW 1/2 - 3/4 turn None
Intermediate pressure Inlet 2,500-3,000 (±100) psi 140 (±5) psi
Intermediate pressure creep Inlet 2,500-3,000 (±100) psi 5 psi max between 5 to 15 seconds
after cycling regulator (purge)
Opening effort Inlet 2,500-3,000 (±100) psi,
intermediate pressure 140 (±5) psi
Knob turned in CW 1/2 - 3/4 turn +.6 to +1.0 inch H20
(no leak)
Knob turned full in CW +2.0 to +2.7 inch H20
Flow effort Intermediate pressure 140 (±5) psi +6 inches H20 (maximum)
at 15 SCFM
Purge flow Intermediate pressure 140 (±5) psi 5.0 SCFM flow rate (minimum)

Impulse Second Stage Service & Repair Manual 17
© 1997 U.S. Divers Co., Inc.
1. Acid Bath - U.S. Divers strongly recommends ChromeSafe™regulator cleaner (P/N 0201-09) for clean-
ing all reusable brass and stainless steel parts. ChromeSafe™is a specially formulated cleaner that does
not harm rubber or Teflon parts, yet effectively removes silicone grease, corrosion, and grime from metal
parts, leaving only a brilliant shine. For best results, soak parts in an ultrasonic cleaner for 5 to 15
minutes, unless the chrome finish is chipped or flaking. Parts with damage to their chrome finish should
be cleaned separately outside the ultrasonic cleaner to avoid agitation. Be certain to isolate more delicate
parts, such as orifice cones, to prevent damage to sealing surfaces.
CAUTION: Harsh acids, such as muriatic acid, may cause damage to parts and must be strictly
avoided. White vinegar, although less effective, is one suitable substitute for ChromeSafe™.
CAUTION: Ultrasonic cleaning times in excess of 15 minutes may damage the chrome finish of certain
parts. Be certain to use a timer, and do not leave parts unattended while cleaning.
NOTE: Although ChromeSafe™contains a degreasing agent, cleaning heavily greased parts in
ChromeSafe™will shorten the effective life of the solution, and require it to be replaced on a more
frequent basis. Heavily greased parts may be degreased in a solution of warm water and mild dish
detergent prior to being placed in the acid bath.
2. Neutralizing Bath (optional) - Mix 1/4 cup sodium bicarbonate to one quart water. Remove parts from the
acid bath and place directly into this solution for 30-60 seconds.
3. Fresh Water Rinse - If tap water is extremely “hard,” distilled water may be used to prevent any mineral
residue. Remove parts from the neutralizing bath and place directly into this rinse. Agitate lightly, and
allow to soak for at least 15 minutes. Remove and blow dry with low pressure (25 psi) filtered air, and
inspect closely to ensure proper cleaning and like-new condition.
ANODIZED ALUMINUM, PLASTIC & RUBBER PARTS
Anodized aluminum parts and parts made of plastic or rubber, such as box bottoms, box tops, dust caps,
etc., may be soaked and cleaned in a solution of warm water mixed with mild dish soap. Use only a soft
nylon toothbrush to scrub away any deposits. Thoroughly blow dry, using low pressure filtered air.
HOSES
If buildup of corrosion is severe, it is permissible to soak only the hose fittings in ChromeSafe™cleaner
as needed, and not allow any solution to enter the hose. Rinse in fresh water and allow to dry with the
cleaned ends hanging down. Blow filtered air through them prior to installing onto the regulator.
LUBRICATION AND DRESSING
All O-rings should be lubricated with Dow Corning® 111 (or equivalent) pure silicone grease only.
Dress the O-rings with a very light film of grease, and remove any visible excess by running the O-ring
between thumb and forefinger. Avoid applying excessive amounts of silicone grease, as this will attract
particulate matter that may cause damage to the O-ring.
Hoses and other black rubber parts may be dressed and preserved using a clean cloth impregnated with a
pump silicone milk.
CAUTION: Aerosol spray silicone must be strictly avoided. Do not attempt to use as a substitute for
silicone grease.
CAUTION: Do not apply any form of silicone lubricant to silicone rubber parts, as this will cause them
to deteriorate prematurely.
ProcedureA
Cleaning&Lubrication
(AllAqua-LungRegulators)

18 Impulse Second Stage Service & Repair Manual
© 1997 U.S. Divers Co., Inc.
LUBRICANT / CLEANER APPLICATION SOURCE
Dow Corning®111 All O-rings; threaded metal parts Dow Corning Corp.
(pure silicone grease) P.O. Box 1767-T
Midland, MI 48640
800-248-2481
Silicone Pump™ General preservative/conditioner for McNett Corp.
(non-aerosol silicone milk spray) hoses, instrument console boots, etc. P.O. Box 996
Bellingham, WA 98227
800-221-7325
Anti-Seize Lubricant #80208 M.A.S. cylinder adapter - female threads Permatex Industrial Corp.
(food grade - U.S.D.A. approved Micra ADJ adjustment screw 705 N. Mountain Rd.
for conformance to MIL-A-907-E) Newington, CT 06111
[phone]
ChromeSafe™ Degreaser and acid bath for reuseable U.S. Divers Co. P/N 0201-09
(ultrasonic cleaning solution) stainless steel and brass parts.
Oakite #31 Acid bath for reuseable stainless Oakite Products, Inc.
steel and brass parts. 50 Valley Road
Berkeley Heights, NJ 07922
White distilled vinegar Acid bath for reuseable stainless "Household" grade
(100 gr.) steel and brass parts.
Liquid dishwashing detergent Degreaser for brass and stainless steel parts, "Household" grade
(diluted with warm water) general cleaning solution for plastic, rubber,
and anodized aluminum parts.
Snoop™ Leak testing Nupro Company
400 E. 345th St.
Willoughby, OH 44094
216-951-7100
TableA
RecommendedLubricants&Cleaners
(AllAqua-LungRegulators)
CAUTION: Silicone rubber requires no lubrication or preservative treatment. DO NOT
apply silicone grease or spray to silicone rubber parts. Doing so will cause a chemical
breakdown and premature deterioration of the material.
CAUTION: Aerosol spray silicone should be avoided because (1) common aerosol
propellants may attack plastic and rubber parts, and (2) because only a slight amount
of silicone remains after the solvent evaporates, and provides no lasting benefit.
CAUTION: DO NOT use muriatic acid for the cleaning of any parts. Muriatic acid,
even when strongly diluted, can harm chrome plating, and may leave a residue that is
harmful to O-ring seals and other parts.