Scubapro S600T Adjustment Knobs

[Lonely Boy]

I am using MK25TA/S600T for recreational diving. There are 2 controls on the 2nd stage - Inhalation Adjustment and VIVA adjustment.

Although I have read the instructional manual and the website description, I am not very sure about the exact use of these adjustments. Would experts here tell me under what diving circumstances I should adjust these 2 knobs?

Thanks.

 

[jamiei]

open them both up (inhalation effort - turn counterclockwise all the way). Leave the Viva wide open all the time. You can back the inhalation effort off during the dive if you need to for some reason.

 

[Lonely Boy]

Thank you for your information.

Does it mean that I should turn them all down when the reg and tank is not in use, such as sit on the boat or when the reg is not in my mouth?

 

[jamiei]

no, you should be able to just open them all up and leave them that way. The viva really doesn't do all that much anyway. If you were to take the cover and diaphragm off the reg, you would see that it is just a simple plastic vane that when turned "down" only serves to block air flow slightly. When you turn it all the way on, it simply lowers this air flow blockage. Seems more like a gimic than anything. People love their gadgets, buttons, and knobs...

 

[pescador775]

The Viva is a deflector plate which is advertised to prevent freeflow when the regulator is dangling in the water. Most people leave it open and adjust flow with the knob. The large knob operates a spring which adjusts tension on the second stage poppet valve seat. This causes the breathing effort to vary and changes the sensitivity to freeflow, a consideration when snorkeling on the surface with the regulator dangling or when facing into a stiff current. This knob should be backed out when the regulator is not in use for a long time to reduce pressure on the seat.

 

[Lonely Boy]

Thank you for the information from both of you.

I really find that the VIVA has made no difference to the performance. However, when the inhalation resistance knob is turned fully outward, it tends to freeflow when I press the purge button on land.