Uwatec D420 Service Manual
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D420 Service Manual
Use this manual at your own risk. It is not approved by Scubapro.
DIY service of scuba life support equipment may kill you.
This manual has been adapted from a copy of Version 1.0, March 2020
D420 SERVICE PROCEDURE, D420 SECOND STAGE GUIDELINES,
DISASSEMBLY, ASSEMBLY, ADJUSTING AND FINAL TEST,
published by Johnson Outdoors. As no copyright notice was observed on the
document, any use of copyrighted material is unintended and inadvertent.
The document had apparently been translated from the Italian, and text has
been modified for clarity where translated phrases were unclear.
The author has made additions and modifications based upon his experience,
which have not been approved by Scubapro.
Use this document at your own risk.

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Summary of Contents for Uwatec D420

  • Page 1 DIY service of scuba life support equipment may kill you. This manual has been adapted from a copy of Version 1.0, March 2020 D420 SERVICE PROCEDURE, D420 SECOND STAGE GUIDELINES, DISASSEMBLY, ASSEMBLY, ADJUSTING AND FINAL TEST, published by Johnson Outdoors. As no copyright notice was observed on the document, any use of copyrighted material is unintended and inadvertent.
  • Page 2: Table Of Contents

    Contents General Notes ..........................Cleaning Procedures ........................Seals and o-rings ........................Plastic or rubber components ...................... Metallic Components ........................Tools ............................Disassembly Procedure ........................ Reassembly Procedure ......................... Tuning and Final Testing ......................General Notes This regulator is designed for use with Enriched Gas (Nitrox) to EAN40. Use only perfectly cleaned tools in a cleaned environment Cleaning procedure Please refer to the "SCUBAPRO CLEANING PROCEDURE"...
  • Page 3: Tools

    Tools • Flat blade screwdrivers, 2.5mm and 5mm • Non-serrated thin bladed, sharp knife • Pin punch (MK2 seat tool) PN 43.300.210 or 1.5mm hex key • Flow Vane Face Spanner PN 43.420.012 or small pin face spanner • Scubapro Multitool PN 43.040.000 or small pin face spanner •...
  • Page 4: Disassembly Procedure

    (44) and spring (43) and set aside. 5. Unscrew the face plate (42), rotating counterclockwise from the case. If necessary, use the SCUBAPRO D420 special tool PN 43.404.003 or a rubberized pad. 6. Carefully lift out the diaphragm thrust washer (41) and the diaphragm (40).
  • Page 5 13. By using a face spanner or tool PN 43.420.012 grasp the tabs on the flow vane ring (31) and unscrew it from the case by rotating counter clockwise. The sub-assembly consisting of the flow vane ring (31), two o-rings (28 and 30), the flow vane (29), the hex adjuster screw (27) and possibly o-ring (34) is now loose.
  • Page 6: Reassembly Procedure

    Reassembly Procedure If the exhaust valve (13) must be replaced, first ensure the land where the valve edge will seal is clean and without scratches. Remove the old valve by cutting the barb of the center silicone nipple where it penetrates the inside of the case. Insert the new valve by carefully pulling on the center nipple from the inside of the case, and ensure that the barb has completely entered the case.
  • Page 7 5. Hold the housing with the square flap facing downward and toward you, and the case with the mouthpiece tube facing toward you. Insert the housing into the support, and using only the ball of your thumb, press it downward fully, engaging the tooth on the housing in the notch of the housing support.
  • Page 8 13. Press fit the flow vane (29) inside the flow vane ring (31), until the vane is up against the ring and the teeth of the two parts are at the same level. Set this assembly aside. 14. Remove the poppet (stem assy) (49) from its paper envelope. Handling it carefully, generously lubricate the .323 o-ring at the base of the poppet (stem assembly) (49).
  • Page 9: Tuning And Final Testing

    Tuning and Final Testing 1. Connect the second stage to the LP hose and pressurize the regulator with 125-145 psi. Using a 5mm hex key, turn the adjustment screw (27) just until there is no air leak. NOTE: Rotating the adjustment screw clockwise increases spring tension on the poppet, and increases inhalation effort (“cracking effort”);...
  • Page 10 6 (Substitute). With the regulator pressurized and with a 0.25-0.5mm gap present between the back of the diaphragm disc and the lever, turn the adjustment screw (27) to change cracking effort. NOTE AGAIN: Scubapro prescribes no gap between lever and diaphragm in the original Service Manual.

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