Tusa TR-350 User manual

TR-350 / TR-390 REGULATOR
TABLE OF CONTENTS
SECTION

PAGE NO.
GENERAL INFORMATION

2
1.0 Important information

2
II

DESCRIPTION AND OPERATION

3
2.0 Nomenclature & Description of Operation

3
2.1 Balanced Piston First Stage

3
2.2 Adjustable Second Stage

4
2.3 Non-Adjustable Second Stage

5
III

GENERAL (USER) RECOMMENDED MAINTENANCE

6
3.0 General Care Guidelines

6
3.1 Determining Service Intervals & Cycle Life

7
3.2 Determining Service Application

8
A)
Exposure of equipment

8
B)
User maintenance

8
C)
Experience and application

8
D)
Future application

8
INSPECTION TECHNIQUES AND TROUBLESHOOTING

9
4.0 Inspection Techniques

9
A)
0-rings

9
B)
Sealing surfaces

9
C)
Hoses & rubber components

9
4.1 Troubleshooting Guidance

9
4.2 Troubleshooting First Stage

10
4.3 Troubleshooting Second Stage

11
V

DISASSEMBLY/ASSEMBLY BALANCED PISTON FIRST STAGE

13
5.0 Disassembly Procedure TR-350/TR-390 Balanced Piston First Stage

13
5.1 Repair & Replacement Schedule TR-350/TR-390 Balanced Piston First Stage 15
5.2 Assembly TR-350/TR-390 Balanced Piston First Stage

16
5.3 Exploded View Balanced Piston First Stage

19
VI

DISASSEMBLY/ASSEMBLY ADJUSTABLE SECOND STAGE

20
6.0 Disassembly Procedure TR-390 Adjustable Second Stage

20
6.1 Repair & Replacement Schedule

24
6.2 Assembly Adjustable Second Stage

24
6.3 Exploded View Adjustable Second Stage

30
VII

DISASSEMBLY/ASSEMBLY NON-ADJUSTABLE SECOND STAGE

31
7.0 Disassembly Procedure SS-350 Second Stage

31
7.1 Repair & Replacement Schedule

34
7.2 Assembly Procedure SS-350 Second Stage

34
7.3 Exploded View SS-350 Second Stage

38
VIII

TUNING AND ADJUSTMENT

39
8.0 TR-350/TR-390 Balanced Piston First Stage Tuning

39
8.1 TR-390 Adjustable Second Stage Tuning

39
8.2 SS-350 Non-Adjustable Second Stage Tuning

42
IX

TORQUE SPECIFICATIONS

43
9.0 Torque Specifications for TR-350/TR-390 Balanced Piston First Stage

43
9.1 Torque Specifications for TR-390 Adjustable Second Stage

43
9.2 Torque Specifications for SS-350 Non-adjustable Second Stage

43
X

ASSEMBLY TOOLS

44
10.1 Assembly Tools Required for the TR-350/TR-390 & SS-350 Regulators

44
XI

LUBRICANTS, CLEANERS & SEALANTS GUIDANCE

45
11.0 General Cleaning Methods

45
11.1 Lubricants and Sealants

45
XII

SPECIAL APPLICATIONS GUIDANCE

46
12.0 Performance Specifications

46
12.1 Maximum Performance Adjustments

46
12.2 Enhanced Air Mixtures & Approved Modifications

46
12.3 Cold Water Diving

46
12.4 Contaminated Water Diving

46

SECTION I
GENERAL INFORMATION
1.0 IMPORTANT INFORMATION
This manual is designed for use by authorized service technicians who have completed a training course.
in TUSA Regulator Repair. This manual is intended for use only in connection with the TUSA Regulator
Repair Course as prescribed by Tabata USA Incorporated and is not meant for general distribution.
Accordingly, Tabata USA makes no representations or warranties of any kind concerning the techniques
or procedures contained within this manual. It is assumed the authorized service personell repairing and
servicing regulators have average mechanical ability, a good understanding of the operation of SCUBA
regulators and adequate diving experience.
This manual is not intended for for use by divers in overhauling or attempted repair of regulators in the
field. Such practice by untrained persons is strongly discouraged and should be attempted only by
trained personell when absolutely necessary.
Copyright 1995 by Tabata USA, Incorporated.
All rights reserved. The contents of this manual constitutes the confidential information of Tabata USA,
Incorporated. Its receipt or possession does not convey any right to reproduce all or any portion or
specification hereof, without the expressed written consent of Tabata USA, Incorporated. All publisher
rights under the copyright law will be strictly enforced.

FIG 2 - 1
SECTION II
DESCRIPTION AND OPERATION
2.0 NOMENCLATURE AND DESCRIPTION OF OPERATION
The following discussion will introduce the proper nomenclature to be used through
this manual. To help establish efficient communications when reporting problems to
the factory or discussions with the customer we recommend that you utilize these
terms. Terms will be introduced in full text followed by the acronym or abbreviation
in parenthesis.
The regulator reduces high pressure air from the scuba cylinder (supply pressure) to
ambient pressure suitable for breathing, through the operation of first and second
stage regulators. The first stage regulator reduces incoming high pressure (HP) air, to
an intermediate pressure (IP) of approximately 135 to 150 pounds per square inch
(psi). The second stage regulator is a diaphragm operated downstream demand
valve and functions to reduce air from intermediate pressure to ambient pressure
permitting normal breathing at depth. The first and second stages of the regulator
are connected by a low pressure (LP) hose. A yoke on the first stage body secures the
regulator to the cylinder valve, while an o-ring surrounding the outlet orifice on the
cylinder valve ensures an airtight connection to the first stage. During servicing and
overhaul, the term supply pressure is used to denote an air supply of high pressure
between 2250 to 3200 psi.
2.1 BALANCED PISTON FIRST STAGE
Refer to figure 2-1 for the following discussion High pressure air entering the yoke
retainer inlet port of the first stage regulator passes through
a sintered filter which
helps prevents the entry of any foreign particles. This air flow continues through the
regulator body passages to the HP seat chamber where it flows across the annular gap
between the HP seat and the end of the HP piston stem. Here the air expands
resulting in a reduction of pressure. Air flow continues past the HP seat, as long as the
piston remains in an OPEN position, and passes through the internal section of the HP
piston stem. The term "flow through piston"
describes this operation. Air emerges from the HP
piston stem and enters the intermediate pressure
chamber inside the upper portion of the cap and
swivel. The LP hoses are attached to the swivel
and guide air flow to the second stage regulator or
buoyancy compensator inflator device.
The forces which tend to maintain the HP piston
in the OPEN position are (1) the force of the HP
spring and (2) the force produced by ambient
water pressure acting on the back surface of the
HP piston head. The force which tends to move
the piston to the CLOSED position is the
pneumatic force produced by the intermediate
pressure acting on the front of the piston head.
The regulator is designed so that the piston
remains in the open position until the intermediate
pressure approaches approximately 135 psi. When this intermediate pressure
IS
achieved the force becomes great enough to overcome the force of the HP spring
and the ambient water pressure allowing the piston to move into the CLOSED
position sealing against the HP seat.

FIG 2 - 2
The piston will remain in the CLOSED position until the intermediate pressure in the LP
hose is lowered by the actuation of the demand lever in the second stage regulator
during inhalation. This lowering reduces the pneumatic force acting against the front
of the HP piston head which permits the combined force of the HP spring and the
ambient water pressure to move the HP piston to the OPEN position allowing high
pressure air to flow into the swivel chamber again.
The first stage piston is pneumatically "balanced" meaning that the high pressure air
surrounding it exerts no opening or closing force against the piston itself. The
advantage of a "balanced" piston is that the first stage regulator maintains a stable
intermediate pressure range of 128 to 145 psi over ambient pressure, despite a
continually decreasing supply pressure from the SCUBA cylinder. This stabilization of
intermediate air pressure in the first stage assures optimal second stage performance as
the air supply in the SCUBA cylinder is depleted.
The balanced piston first stage of the TR-390 Regulator functions to deliver the
intermediate pressure at 135 to 150 psi above the depth related ambient pressure.
This depth compensation is achieved by allowing ambient water to enter the main
body and flood the HP spring area and act upon the back side of the HP piston. As
the diver descends the ambient water pressure becomes the reference point from
which the HP piston controls the intermediate pressure from 135 to I 50 psi above
ambient pressure. The balanced piston first stage maintains a constant differential
between surrounding ambient water pressure and intermediate air pressure. This
helps to assures that the effort to actuate the second stage will remain relatively
constant with changing depth.
2.2 ADJUSTABLE SECOND STAGE
Refer to figure 2-2
for the following discussion. The second stage of the TR-390 is a
"demand" type regulator which acts to convert the intermediate air pressure into a
near ambient inhalation pressure. During the inhalation cycle the air pressure within
the second stage case drops below the ambient water pressure acting on the outside
surface of the diaphragm. This "differential pressure" causes this flexible diaphragm to
move inward to counteract the dropping (negative) inhalation pressure. As the
diaphragm flexes inward it depresses
the demand lever which in turn pivots
and lifts the poppet assembly off the
seat of the adjustable orifice inside the
coupler. This allows air at intermediate
pressure to flow into the case of the
second stage at a rate directly related to
the differential pressure created across
the diaphragm. The resulting reduction
in intermediate air pressure in the first
stage now causes the HP spring to lift
the HP piston off the HP seat allowing
supply (pressure) air to flow from the
cylinder.
As inhalation decreases, the diaphragm returns to a normal state causing the
demand spring to seal the poppet assembly against the seat. The demand lever
and poppet move to a closed position stopping air flow. The first stage now senses
an intermediate pressure returning to a normal state allowing the HP piston to
overcome the force from the HP spring and seal off air flow from the supply
(cylinder). During exhalation, increasing (positive) pressurein the second stage case
causes the exhaust valve to open discharging exhaled air into the sea, This
operation is repeated during every breathing cycle.
O

The second stage valve mechanism is termed a "downstream demand valve". If the
intermediate pressure were to increase beyond the sealing capability of the demand
spring, the valve automatically opens and functions as a pressure relief valve. This
protects both the first stage regulator and the second stage hose assembly from over
pressurization while allowing air to flow to the diver for safety.
The TR-390 and SS-350 second stages utilize two variants of the downstream demand
valve. The TR-390 is an adjustable second stage demand valve. The SS-350 is a non-
adjustable second stage demand valve. The TR-390 has two springs which generate
sealing force sufficient to prevent airflow past the adjustable orifice and the poppet
seat. The first spring is the demand spring acting directly on the poppet seat, The
second spring is the secondary spring and acts to help push the poppet against the
seat. The secondary spring compressed height is controlled by the diver turning the
demand knob. As the demand knob is turned clockwise (when viewed head-on) it
compresses the secondary spring allowing it to increase the total sealing force
between the poppet and seat. As this sealing force increases, so does the effort
required by the diver to generate a greater differential pressure across the diaphragm
leading to valve actuation and air flow.
2.3 NON-ADJUSTABLE SECOND STAGE
Refer to figure 2-3 for the following discussion. The SS-350 works exactly like the TR-
390 valve except for the fact that the valve has only one spring. The demand spring
in the SS-350 can generate enough sealing force to prevent air flow from the poppet
seat and orifice. It does not need the assistance provided by the absent secondary
spring. The SS-350 demand spring is "stronger" than the TR-390 demand spring. It is
important to remember this to avoid interchanging them during stocking or overhaul.
These springs are not interchangeable. Refer to Section 6.0 for further discussion.
FIG 2 - 3
CAUTION
Use caution not to confuse or use the wrong demand spring when assembling all
second stages, as each primary second stage spring exerts a different sealing force.
Please refer to the appropriate schematic for correct part numbers.

SECTION HI
GENERAL (USER) RECOMMENDED MAINTENANCE
3.0 GENERAL CARE GUIDELINES
TUSA recommends to all Authorized Dealers that they take individual time with each
customer to explain and demonstrate the following simple steps for care and
maintenance of the regulatorThis will help to insure the following goals:
Personalized contact with the customer insuring satisfaction.
Help to insure long life of the new purchase through maintenance.
Communication of findings during tuning or overhaul service.
Help prevent problems described if this step is not taken.
1 After exiting the water and with the cylinder valve still on, purge air through the
second stage to help blow out remaining water.
2. Close cylinder valve and purge remaining pressure from the regulator. Loosen the
yoke knob and remove the first stage from the valve. Crack the valve slightly to
direct a stream of air onto the dust cap to dry it off. Immediately place the dry dust
cap over the conical filter and tighten the yoke knob to prevent moisture from
entering the first stage. The conical filter is a nickel plated sintered brass component
whose metallic matrix structure creates a large filtration area allowing for efficient air
filtration with low pressure drop. This large area makes the filter susceptible to
corrosion by trapping tiny droplets of water within it's matrix.
3. Prior to rinsing the regulator insure the dust cap is snug and covering the conical
filter area of the yoke. If using the TR-390 IMPREX AD2 Adjustable second stage,
dial the adjustment knob fully clockwise in to prevent water from entering into the
hose and first stage.
Using either of the following rinse methods is necessary. A stream of fresh water,
from a hose or faucet, directed around and especially into the holes in the first
stage will flush salt water from the piston and spring area preventing corrosion and
minimal deposits. Direct fresh water into the mouthpiece of the second stage to
flush the internal components, diaphragm and exhaust valve area. The build up of
mineral (salt) deposits will lead to premature wear on the 0-rings of the first stage
piston and lead to a rough breathing second stage valve mechanism.
OR
Immerse the regulator (make sure dust cap is in place) into a bath of fresh water and
agitate to insure good flushing. If extended storage is anticipated, immersion for 12
hours or more is preferred. After immersion, utilize the rinse step above to flush all
regulator components thoroughly
NOTE
Do not depress the purge button of the second stage while rinsing or soaking. This will
help prevent water from entering the valve mechanism or intermediate pressure hose
causing corrosion or deposits.
5. Before storing the regulator, hang it with the second stage down to insure
drainage and ample time to completely dry all components. If
a cylinder is available,
the user may wish to install the regulator and purge air through the system to
insure no water remains within the valve mechanism prior to storage.

EMPHASIZE THE FOLLOWING TO YOUR CUSTOMERS:
WARNING
DO NOT expose the regulator to extreme heat or direct sunlight when not in use.
Temperatures exceeding 180 °F for extend periods of time may cause permanent
damage to some internal valve components leading to lack of performance or failure.
If you suspect your regulator has been exposed to excessive heat, please have it
examined by your authorized TUSA Service Center,
DO NOT leave the regulator pressurized or attached to a SCUBA cylinder for an
extended period of time when not in use.
DO NOT lift the SCUBA cylinder by using the regular hoses or first stage as a handle.
Always secure the cylinder to prevent it form tipping over and damaging the
regulator while it is attached.
3.1 DETERMINING SERVICE INTERVALS & CYCLE UFE
TUSA recommends that the Service Technician utilize the following guidelines to
determine service intervals & extent of service required for the customers regulator.
Most components in a regulator have very high expected usable life based on the
number of breathing cycles and exposure of the equipment.
The following calculation is meant to educate the Service Technician on how many
cycles (breathing) a regulator may see from average use.
CYCLES = DIVE DAYS/YEAR X DIVE HOURS/DAY x 20 BREATHS/MIN X 60
MIN/HOUR
If you assume 25 dive days per year and 3 diving hours per diving day:
CYCLES = 25 DAYS/YEAR X 3 HOURS/DAY x 20 BREATHS/MIN X 60 MIN/HOUR
BREATHING CYCLES = 90,000 per year
If you were to calculate this for rental equipment, assume 240 rental days per year
and 4 dive hours per day:
CYCLES = 240 DAYS/YEAR X 4 HOURS/DAY x 20 BREATHS/MIN X 60 MIN/HOUR
BREATHING CYCLES = I ,I52,000 per year
Yes, that is correct:
ONE MILLION ONE HUNDRED FIFTY TWO THOUSAND BREATHING CYCLES!
Now for your own information, calculate what you would expect for an average
customer on one 2 week dive boat vacation making 3 to 5 dives per day less than 60
feet deep.

3.2 DETERMINING SERVICE APPLICATION
As you can see, it is important to determine your customers dive habits to determine
the best possible recommendation for service. Other factors to consider include
exposure of equipment, extent of user maintenance, experience and application from
the user and future planned use of the equipment. To summarize:
EXPOSURE OF EQUIPMENT
Diving cold water (40 °F or lower) requires the regulator to be "Environmentalized" or
protected from potential freezing and requires more frequent servicing. (See Section
12.3)
Diving in low visibility or contaminated water requires more frequent servicing and
overhaul to keep residue from building up inside valve components. (See Section 12.4)
Diving in tropic salt water environments tends to subject the regulator to constant
moisture exposure and will lead to accelerated corrosion of regulator valve
components.
Diving with Enhanced Air (Safe Air) mixtures requires the regulator to be specially
cleaned and lubricated. (See Section 12.2)
USER MAINTENANCE
Obviously a regulator that has been maintained extensively by the user will require far
less overhauls to replace worn or corroded components. Poor user maintenance
indicates that more attention (overhauls and
tuning) of the regulator is required to
prevent failures.
EXPERIENCE AND APPLICATION
Deep diving or overhead environment diving requires a regulator to be in top
condition at all times. The experienced user would require more frequent overhauls
and replacement of key o-rings and first stage spring to maximize reliability.
FUTURE APPLICATION
A user planning an extended dive vacation training or use for applications discussed
above would benefit from a overhaul prior to the planned extended use to insure
maximum performance and reliability.

SECTION IV
INSPECTION TECHNIQUES AND TROUBLESHOOTING
4.0 INSPECTION TECHNIQUES
We encourage the service technician to develop good habits and practice in
inspection techniques during service and overhaul. Observing the exterior condition
of a regulator can offer clues on what may be found during overhaul. Finding sand
or salt deposits on the exterior crevices between mating parts may indicate a
regulator that is not properly maintained by the customer. One may almost certainly
discover more sand or salt deposits inside the second stage case. In severe instances,
a major overhaul and adjustment would probably take less time to accomplish than
to attempt a light cleanup leading to marginal performance adjustment. Severe
dings in the chrome plated brass body of the first stage or plastic case of the second
stage may indicate gross negligence in handling the regulator. Further examination
must proceed especially looking for small cracks or damage in the second stage body,
LP hoses, yoke knob etc... It is most important to look for cracks or damage near the
inlet coupler of the second stage case. Mishandling may lead to severe stress
imparted into the LP hose resulting in cracks. Please refer to Section 6.0, Figure 6-8
for further discussion.
0-RINGS
0-rings are common off-the-shelf well engineered reliable sealing devices. A few
words about handling them is required. 0-rings can be ordered in different sizes,
rubber compounds and hardness (durometer). It is important not to substitute o-
rings from other sources in replacing TUSA regulator seals. Use only factory supplied
o-rings. As part of the TUSA annual servicing policy it is recommended that
all o-rings
be replaced to maintain the warranty. Further details are available from the factory
distributor. Do not attempt to clean or lubricate o-rings outside of the
recommendations found in Section I 1.0
SEALING SURFACES
All metal parts used in TUSA regulators are made of either a corrosion resistant
stainless steel or chrome plated brass. Handle all metal components with care to
avoid scratches, dings or dents. Some components such as the first stage piston in
both the TR-350 & TR-390 regulator have a very smooth and polished surface on the
stem. This is the sealing surface for the HP o-ring. A very unnoticeable scratch or
ding on this surface may allow a high pressure leak across the o-ring. The piston
cannot be repaired and thus becomes an expensive replacement which could have
been avoided with proper handling. Pay particular attention to the assembly of all
components and which surfaces are used for sealing against o-rings. Handle these
surfaces with particular care to avoid scratches dings or dents.
HOSES AND RUBBER COMPONENTS
The examination, care and handling of all rubber components is well documented
throughout the TUSA Dealer Service Manual. Look for deterioration and cracking of
rubber components resulting from age, misuse, or exposure to caustic cleaning
compounds. Contact your factory representative should you have further questions.
4.1 TROUBLESHOOTING GUIDANCE
Prior to troubleshooting the TUSA IMPREX 2 or IMPREX AD2 regulator we recommend
you become familiar with the operation and design by reading Sections 2.0 and 5.0
through 8.0. You will find that a good basis and understanding of the regulator
function will benefit your repair and servicing abilities.

Prior to beginning a service or troubleshooting session it is important to proceed as
follows.
1.
Talk to the customer. Attempt to understand the nature of the problem. If the
customer describes for instance, "sporadic periods of high inhalation efforts" ask the
obvious question: "Did you happen to be swimming upside down when the
regulator seemed to breath harder?" Discussions may lead to understanding your
customer and his complaints better.
2.
Attempt to duplicate the functional problem by doino an In-Water Test. A reported
leak or bubble from the first stage may be traced to a specific 0-ring much quicker
with this method.
3.
Record your findings as you examine and test the regulator prior to and during the
entire service and overhaul procedure. Record The customers name, date of last
service, intermediate pressure before and after service, supply pressure during
testing, unusual conditions or debris present, components and seals replaced
during this service, approximate breathing cycles between service periods. and any
other pertinent information.
4.2 TROUBLESHOOTING TR-350/TR-390 BALANCED PISTON FIRST STAGE
SYMPTOM  POSSIBLE CAUSES 
RECOMMENDATIONS
LOW FLOW OR HIGH INHALATION EFFORTS
1. Cylinder valve not open

I . Open valve completely
or clogged.

or overhaul needed.
2. Sintered filter (7) clogged.

2. Replace sintered filter.
3. HP spring (18) coil weak or fatigued.

3. Replace HP spring.
INTERMEDIATE PRESSURE LOW OR UNSTABLE
1. HP piston head o-ring (21)
damaged.
2.
HP piston (20) sealing edge
damaged or HP seat (10) bad.
3. Washer ( I 9) installed incorrectly
or wrong size.
4.
HP piston stem o-ring (17)
worn or leaking.
5. Filter housing (9) loose.
6. Leak between intermediate chamber,
LP hose, and second stage.
7.
Cap (24) loose.
1.
Replace o-ring, check seal worn or
damaged.
2.
Replace HP piston & HP seat.
3. Replace washer.
4.
Replace o-ring, check seal.
5. Tighten filter housing.
6. Find leak in-water test.
7.
Tighten cap.
INTERMEDIATE PRESSURE EXCESSIVELY HIGH
1.
HP Piston (20) sealing edge
damaged or HP seat (10) bad.
2. Washer (19) installed
incorrectly or wrong size.
3.
HP piston o-rings (1 7) & (21)
are worn or leaking.
1. Replace HP seat & check
HP piston sealing edge.
2. Replace washer
3.
Replace o-rings, check seal.
AIR LEAKS DETECTED FROM IN-WATER TEST
1.
HP piston o-rings (17) & (21) 
I . Replace o-rings, check seal.
are worn or leaking.
2.
Cap o-ring I 1) is worn.

2. Follow special procedure
Section 5.1 & 5.4 only
10

3. LP port plug 0-rings (23)  3. Replace o-rings, check seal.
are worn or leaking.
4.3 TROUBLESHOOTING SECOND STAGE
The following guide applies to both adjustable and non-adjustable second stage.
Note the position of the adjustment knob as you utilize the following
recommendations.
SYMPTOM 
POSSIBLE CAUSE  RECOMMENDATIONS
LOW FLOW OR HIGH INHALATION
1.
Cylinder valve not open
or clogged.
2. Insufficient intermediate
pressure from first stage.
3. Demand lever bent.
4. Adjustable orifice too far in.
Check seal edge condition.
5. Too much demand lever slack.
6. Locknut overtighten onto
poppet shaft
7.
Locknut too loose.
8. Piston (28) contaminated.
and clean all parts.
EFFORTS IADJUSTMENT KNOB OUT)
1. Open valve completely
or overhaul needed.
2. Check first stage P
Also check supply pressure.
3. Replace demand lever.
4.
Adjust per Section 8.1
5.
Adjust per Section 8.1
6. Adjust per Section 8.1
7.
Adjust per Section 8.1
8. Disassembly adjustment tube
ADJUSTMENT KNOB DIFFICULT TO TURN OR NO ACTION
I . Piston (28) or follower (30)
is contaminated.
2. Follower is stripped onto
stem (31).
3. Poppet and demand lever action
are sticky or damaged.
4. Secondary spring (29) corroded
5. Stem (31) threads are
corroded.
6. Debris trapped between knob
and packing nut (34).
7.
Thrust washer (33) absent,
contaminated, or worn.
1. Disassembly Adjustment tube
and clean all parts.
2. Replace follower
3. Disassemble valve and clean.
4. Replace secondary spring.
5. Disassemble and clean.
6. Disassemble and clean.
7.
Clean or replace with new
thrust washer.
PURGE FUNCTION IS ABSENT OR LOW FLOW OR RATTLE HEARD INSIDE
1. Cylinder valve not open
or clogged.
2. Insufficient intermediate
pressure first stage.
3. Demand lever bent
4. Adjustable orifice turned
too far in.
5. Too much demand lever slack.
6. Locknut overtighten onto
poppet shaft.
7. Locknut too loose.
1.
Open valve completely
or overhaul needed.
2.
Check first stage IP.
Also check supply pressure.
3. Replace demand lever.
4.
Adjust per Section 8.1
Check seal edge condition.
5. Adjust per Section 8.1
6. Adjust per Section 8.1
7. Adjust per Section 8.1
Ia

FREEFLOW OR LEAKAGE PRESENT (ADJUSTMENT KNOB TURNED IN)
1. Purge button stuck open.
2. Excessive intermediate
pressure first stage.
3. Demand lever bent
4. Adjustable orifice turned
too far out.
5. Damaged poppet seat (8) or
sealing edge of orifice ( II).
6. Locknut overtighten onto
poppet shaft.
7.
Washer (16) bent.
8. Inlet coupler (10) loose.
9. Demand spring (6) weak.
WATER ENTERING SECOND STAGE
I . Exhaust valve (5) distorted
worn, or bad.
.2. Diaphragm (24) not seated or
torn.
3. Tear in mouthpiece ( I ).
4. Cracked or damaged case (27).
5.
Stem o-ring (32) worn or
absent.
6. Adjustment tube o-ring (26)
cut or absent.
1. Clean purge button.
2.
Check first stage IP
3 Replace demand lever.
4. Adjust per Section 8. I
Check seal edge condition.
5.
Replace poppet seat or
adjustable orifice.
6. Adjust per Section 8.1
7. Replace washer.
8. Tighten per Section 6.2
9. Replace demand spring.
1. Repair or replace exhaust
valve.
2. Reseat or replace diaphragm.
3. Replace mouthpiece.
4. Replace case.
5.
Replace o-ring.
6. Replace o-ring.

SECTION V
DISASSEMBLY /ASSEMBLY BALANCED PISTON FIRST STAGE
NOTE
Prior to disassembly, record the results of the the preliminary inspection, the in-water
test, and the first stage intermediate pressure. Remember to retain all o-rings, filters or
other components which need replacement in case the customer requests to view the
parts. For part replacement, as part of the annual service, please return these parts to
your TUSA factory distributor.
Remember to record your findings as you proceed to allow both a complete record of
overhaul and future reference for servicing.
The words "RECORD FOR REPLACEMENT" will indicate all components to be handled
in this manner.
Read and understand the Troubleshooting Section 4.0 to gain a better idea of which
internal parts may be worn, and to better advise your customer of the service that is
required.
Refer all item numbers (99) to the exploded view for this regulator found at the end of
this section.
5.0 DISASSEMBLY PROCEDURE TR350/TR-390 BALANCED PISTON FIRST STAGE
1 Before disassembling the first stage, remove all attached hoses and port plugs.
Remember to use the proper wrench with each hose as required: low pressure
second stage hoses use a 9/16" open end wrench, low pressure inflator hose use
either a 9/16" or 1/2" open end wrench, and high pressure gauge hose(s) use a
5/8" open end wrench.
2.
Prepare to remove the endcap (24) by inserting one 3/16" Allen wrench into one of
L.P plugs (22) on the end cap and
one 3/16" Alien Wrench into one of
the H.P plugs (15) on the body ( I 3)
as shown in figure 5-1,
3.
Holding the regulator firmly in place
as shown in figure 5.1 twist the
endcap (24) in a counterclockwise
direction until cap (24) is loosened
enough to complete removal by
hand.
FIG 5-1
NOTE
Make certain the alien wrenches are firmly seated into both plugs (15) & (22) before
attempting to rotate the cap (24) in a counterclockwise direction.
4. Remove all L.P Plugs (22) from cap (24) and all H.P Plugs (15) from body (13) with
the same 3/16" Allen wrench.
5.
Remove and inspect the 0-Rings now visible on all these items for any sign of decay
(see Section 4.0 INSPECTION TECHNIQUES for guidance). RECORD REPLACEMENT
if found.
6.
Remove the HP piston (20) from the body (13) by carefully grasping the piston
between thumb and forefinger, pulling straight up with a slow, steady force.

FIG 5-4
WARNING
Failure to recognize or replace a faulty HP piston may lead to failure of the regulator to
regulate the intermediate pressure. Use prudence and replace the piston if damage
to the piston stem sealing edge is found.
7.
Remove the washer (19) from the base of the piston head and inspect this area for
signs of rust. Also inspect the piston stem for unusual scratches, dings, dents or
wear along it sealing surface. Closely inspect the sealing edge of the piston stem
for cracking, dings or dents. Record your findings on the condition of the piston.
RECORD FOR REPLACEMENT and DO NOT attempt to reuse if any of these
conditions are found. See Section 4.0 for important guidelines.
8.
Remove the HP spring (18) and inspect it for any anusual cracks, rust or bent coils.
RECORD FOR REPLACEMENT and DO NOT attempt to reuse if any of these
conditions are found. See Section 4.0 for important guidelines.
WARNING
Failure to recognize or replace a faulty HP spring may lead to failure of the regulator
to supply air. Use prudence and replace the HP spring regularly to maintain top
performance in the regulator function.
9.
Remove the piston head o-ring (21) and RECORD FOR REPLACEMENT. If the
piston will be reused, take steps at this time to protect the piston stem sealing edge
from damage during handling.
10. Remove the piston stem o-ring (17) from the body (13).
NOTE
Removal or replacement of the piston stem o-ring (17) located within the internal o-
ring groove of the main body (13) must be
attempted using only the proper tools and
patience. View the main body through the piston entrance to locate the internal o-
ring groove. The piston stem o-ring
(17) seals against both the stem of the
HP piston (20) and the brass internal o-
ring groove within the main body.
Extreme care must be taken not to
damage the brass sealing surface of the
groove when removing or installing this
o-ring. Use only soft brass or plastic o-
ring pick to attempt this operation.
Examine the o-ring upon removal and
RECORD REPLACEMENT. DO NOT
attempt to reuse this o-ring. Refer to
figure 5-4.
I I Remove the yoke knob (2) and the dust cap (3) from the yoke (5.
12. Inspect the yoke (5) very thoroughly for cracks, wearing, or distortion. If none are
present and the yoke shows no signs of deterioration, it need not be removed to
service the first stage. However, to remove the yoke (5) from the main body. we
recommend using a 1" socket wrench or slotted flat bar tool as shown in figure 5-
5. Place the first stage in a smooth-jawed vise, with yoke facing up. Install the

socket or flat bar tool onto the yoke
retainer nut. Using firm, steady force,
rotate the tool in a counterclockwise
direction until the yoke retainer nut
and yoke are removed
NOTE
Use care and caution to avoid damage
to the hex surface of the yoke nut. DO
NOT overtighten the vise onto the soft
brass parts of the first stage.
FIG 5 - 5
13.
After removing the yoke retainer nut from the body (13), remove and inspect the
yoke for any
signs of distortion or cracking. RECORD FOR REPLACEMENT if found.
14.
To remove the conical filter (7), first remove the filter housing assembly with 3/8"
alien wrench use a sharp pick to remove the filter retainer (6) from the housing (9).
The conical filter and the filter o-ring (8) should drop in your hand. Examine and
record the condition of the conical filter looking for large particles of rust, debris,
corrosion, or dark deposits from excessive contamination. RECORD FOR
REPLACEMENT and DO NOT attempt to reuse.
15.
To remove the HP seat (10) tap the body (13) lightly against
a
soft surface with the
yoke section in the down position. If H.P seat (10) does not dislodge and fall out
by itself push it out from opposite end with a 3/16" Allen wrench. Examine and
record your findings on the condition of the HP seat looking for deep indentations,
contamination, severe discoloration or debris. RECORD FOR REPLACEMENT and
DO NOT attempt to reuse if any of these conditions are found. Section 4.0 for
important guidelines.
NOTE
DO NOT attempt to remove the HP seat from the body by inserting any sharp
instrument. Doing so will cause damage.
16.
Use a nylon bristle brush or toothbrush to remove any Loctite residue found on
the threads or yoke retainer nut (4) and main body
(13).
It is important to do this
prior to cleaning.
This concludes the disassembly of the TR350/TR-390 balanced piston first stage. Please
refer to the Section I 1.0 for proper guidance on cleaning.
5.1 REPAIR AND REPLACEMENT SCHEDULE TR-350/TR-390 BALANCED PISTON
FIRST STAGE
The following repair and replacement schedule
IN
recommended for the TR-350/TR-
390 Balanced Piston First Stage. TUSA recommends full replacement of
all soft seals (o-
rings & seats) according to service use and cycle life of the regulator as discussed in
Section 3.0 Annual service requires replacement of all soft seals at a minimum of 1 year

FIG 5 - 7
The mandatory replacement of the HP
spring is required after a maximum life
of 750,000 (seven hundred fifty
thousand cycles) based on excessive
exposureto corrosion of high
performance use. Refer to figure 5-6
for a view of all soft seals and
hardware.
FIG 5
- 6
5.2 ASSEMBLY TR-350/TR-390 BALANCED PISTON FIRST STAGE
NOTE
Prior to assembly, ensure that all parts have been inspected (both new and those
that are being reused) and are of top quality. Ensure that all o-rings are clean,
supple and lubricated as described in Section 11. Double check to make sure all o-
rings are of the proper size and are
being handled and installed per this
procedure.
1.
Lubricate and install the HP piston
stem o-ring (17) into the main body
(13) using a plastic 3/16" dowel and
a blunt o-ring pick. Use the pick
from the piston end of the body and
the plastic dowel from the HP seat
side. Manipulate the o-ring into the
internal groove of the main body.
Refer to figure 5-7.
NOTE
Replacement of the piston stem o-ring (17) located within the internal o-ring
groove of the main body (13) must be attempted using only the proper tools and
patience. View the main body through piston entrance to locate the internal o-
ring groove. The piston stem o-ring seals against both the stem of the piston (20)
and the internal o-ring groove within the main body. Extreme care must be taken
not to damage the brass sealing surface of the o-ring groove when removing or
installing this o-ring.
2.
Lubricate and install the piston head o-ring (21) onto the head of the HP piston
(20).
WARNING
Failure to recognize or replace a faulty HP piston may lead to failure of the regulator to
regulate the intermediate pressure. Use prudence and replace the piston if damage
to the piston stem sealing (knife) edge is found.
3 Apply a light film of lubricant (see section 11.0) to both sides of the washer ( 19).
Install over the piston stem onto the head of the piston.
4. Apply a very light film of lubricant to both ends of the HP spring (I 8) and place
into the spring cavity of the main body (13).