RS-790 TUSA Regulator
The RS-790 delivers performance, durability and comfort making it the ideal choice for discerning divers.
The R-700 is a balanced diaphragm first stage designed for cold-water use, it features a dry ambient pressure chamber that prevents water contact with the diaphragm maximizing performance in temperate water conditions below 50°F/10°C. Additionally, the R-700 has an external rib section that nearly doubles the surface area for thermal exchange further reducing ice formaton that can lead to freeze up in extreme conditions. The R-700 has two high pressure ports and four low pressure ports including two high flow (HF) that deliver up to a 15% increase in air flow. It is available in both INT (yoke) and DIN versions.
The S-90 second stage is a compact pneumatically balanced system that features a composite housing which insulates and protects under extreme cold-water conditions. The S-90 is equipped with a built-in venturi adjustment lever allowing the diver to select a surface or minimum setting reducing possible free flow or a dive setting for maximum air flow during the dive.
The RS-790 offers the following features:
R-700 First Stage
Dry Ambient Pressure Chamber
The dry ambient pressure chamber on the R-700 prevents water contact with the diaphragm and spring maximizing performance, at any depth, in cold water conditions below 50°F/10°C.
Ideal For Cold Water Environments
The R-700 is engineered for cold water diving. It features a ribbed top cap section that acts like a radiator to increase the surface area for heat transfer. This design allows warming of the critical internal first stage parts that can freeze due to the gas pressure drops and low temperatures.
High Flow Ports
Two high flow low pressure ports are available on the R-700 in addition to two standard LP ports and 2 HP ports. The high flow ports are positioned near the diaphragm and offer up to a 15% increase in air flow.
S-90 Second Stage
Pneumatically Balanced System
The S-90 second stage is a pneumatically balanced design. A small chamber positioned at the end of the poppet assembly traps air and forces the poppet back against the intermediate pressure orifice. This provides decreased inhalation resistance and increases smooth breathing in all conditions.
Venturi Adjustment Lever
The S-90 is equipped with a built-in Venturi adjustment lever. Two positions are selectable by the diver. Use Surface or the minimum setting when entering the water or on the surface, reducing the sensitivity and possible free flow of the second stage. Use the Dive or maximum setting for maximum air flow during the dive.
First stage (R-700)
> Balanced diaphragm first stage with anti-freeze system
> Dry ambient pressure chamber ideal for temperatures below 50°F/10°C
> Ribbed section to increase heat transfer and resist freezing
> Two H.P. ports and Four L.P. (2 standard/2 high flow) ports
> High flow L.P. ports offer up to 15% increase in air flow
> DIN version available as RS-790 DIN (300bar/4350psi)
> Eligible for TUSA CARE Free Parts for Life Program
Second stage (S-90)
> Lightweight, compact composite case design
> Pneumatically balanced system
> Venturi adjustment lever
> Ortho-consciously designed mouthpiece
> Eligible for TUSA CARE Free Parts for Life Program
Environmentally Sealed 1st Stage
The use of a secondary diaphragm and piston sealing the 1st stage preventing contamination or freezing when the regulator is submersed in contaminated or freezing water.
Ortho-conscious Mouth Piece
The ortho-conscious mouth piece feature prevents jaw fatigue. The ridges and flexible material allow the diver to have more control of the mouth piece and reduces tension in the jaw.
Cold Water Ready
The cold water ready feature enables the diver to use the regulator in water temperatures below 50°F/10°C.
Advanced Flow System
The advanced flow system allows ease of air flow and makes air delivery smoother due to the curved housing structure.
Pneumatically Balanced 2nd Stage
A balance chamber added to the regulator 2nd stage, providing equal pressure to both sides of the LP seat greatly reducing inhalation effort.
TUSA Regulators are BALANCED PISTON and BALANCED DIAPHRAGM type SINGLE HOSE REGULATORS. The regulator reduces high pressure air from the scuba
cylinder to ambient pressure suitable for breathing, through the operation of ﬁ rst and
second stage regulators. The ﬁ rst stage regulator reduces incoming high pressure
air, to an intermediate pressure of approximately 135PSI ( 9.5bar). The second
stage regulator, using a diaphragm operated demand valve, further reduces air from
intermediate pressure to ambient pressure permitting normal breathing. The ﬁ rst and
second stages of the regulator are connected by a low pressure hose. A swivel yoke
(TYPE INT) on the ﬁ rst stage body secures the regulator to the cylinder valve, while
an O-ring surrounding the outlet oriﬁ ce on the cylinder valve ensures an airtight connection to the ﬁ rst stage.
R-700 ﬁ rst Stage
The R-700 is a balanced diaphragm first stage with key design and performance
1) Four intermediate pressure ports and two high pressure ports, 2) Balanced ﬁ rst
stage, with a built-in antifreeze system, 3) Replaceable HP seat and HP poppet for
durability and servicing, 4) Two special high ﬂ ow LP ports (HFP) close to the diaphragm offer approximately 15% greater air ﬂ ow, 5) Dry balance chamber prevents
water contact with the diaphragm and the spring for superior cold water performance. The R-700 meets the European Standards EN250:2000 requirements for
cold water conditions.
Do not attempt to connect low pressure hoses to the high pressure ports with the use
of an adapter. Improper connection will cause damage to the equipment and could
result in serious personal injury. Low pressure components are not intended to
withstand pressures greater than 28Bar ≒(400 PSI). When installing your accessory
hoses, avoid damaging the O-ring. Tighten gently, but firmly into the first stage housing.
SCUBA complying with EN 250 are not intended for more than one user to breathe from
at the same time.
If SCUBA are configured and used by more than one diver at the same time, then the
cold water and breathing performances may not fulfil the requirements of EN 250.
PRE-DIVE OPERATING INSTRUCTIONS
1. Position the tank valve so the outlet points toward the diver.
2. Remove the dust cap from the first stage inlet and place the yoke (or DIN adaptor)
in the center of the cylinder valve connection.
3. Position the first stage body so that the second stage hose goes over the right
shoulder of the diver.
4. Hand-tighten the yoke screw or DIN adoptorscrew.
5. Check all the hose connections to the first and second stages. If they can be
loosened by hand, they should be tightened with a wrench before pressurizing.
6. Check the submersible pressure gauge to make sure it indicates zero pressure.
7. Open the tank valve slowly to gradually allow air into the regulator.
NOTE: During this operation, depress the second stage purge button to reduce
shock to the valve mechanism. Do not perform this operation in a cold environment
below 10°C (50°F). Performing this in a cold environment may cause “freeze-up” of
the regulator which can render it inoperable. If this occurs, you should contact a
TUSA authorized service center.
8. Check the submersible pressure gauge to ensure that it indicates the proper tank
Check the tank/regulator connection for leakage. If leakage exists, it may be caused
by incorrect mounting of the regulator on the tank valve, or by a damaged O-ring in
the tank valve.
10. To confirm that the regulator delivers air properly, first exhale through the
mouthpiece to blow any foreign matter out of the second stage, then inhale. A few
of these breathing cycles should immediately indicate proper function.
11. If you are using the second stage as an Octopus regulator, it is strongly recommended to utilize an Octopus plug to prevent any foreign matter from entering the
second stage through the mouthpiece.
12. When the second stage is not in your mouth, uncontrolled air delivery can take
place. This can be stopped by turning the second stage upside down and allowing
it to fill with water. Should the air delivery continue, abort the dive and have the
regulator inspected by a TUSA Authorized Service Center.
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