30-some Year Old US Divers 1st.

[PanamaMike]

My brother uses the US Divers 1st he bought about 38 years ago. He has it periodically serviced but when I checked his IP yesterday it was 125. Looks like a balanced diaphragm design. Does anyone know (i) what the IP should be and (ii) how to adjust it. There's a 1 inch diameter cover with a flat slot but I don't know if that's a cover of the tension adjustment. Any advice appreciated. I wasn't able to find a service manual from the usual sites.

 

[northernone]

Since the respectible posters havent replied yet...

Carefully turning that slot will adjust the IP. Can you upload a photo to help us ID the reg. Could be 135psi depending the model.

 

[tech3324]

Does it look like this?

 

[JamesBon92007]

My brother uses the US Divers 1st he bought about 38 years ago. He has it periodically serviced but when I checked his IP yesterday it was 125. Looks like a balanced diaphragm design. Does anyone know (i) what the IP should be and (ii) how to adjust it. There's a 1 inch diameter cover with a flat slot but I don't know if that's a cover of the tension adjustment. Any advice appreciated. I wasn't able to find a service manual from the usual sites.

My 50-year-old (more or less) Calypso reads about 127. It's not adjustable so the "standard" methods of increasing the IP is to add a stainless steel washer or two beneath the spring. This will increase the IP however when I have attached the second stage to another first stage with an IP of between 135 and 140 it did not seem to improve the ease of inhalation any noticeable amount and it's already adjusted to just below the point where it would not shut of. My point is: don't expect too much after you adjust it

 

[2airishuman]

My brother uses the US Divers 1st he bought about 38 years ago. He has it periodically serviced but when I checked his IP yesterday it was 125. Looks like a balanced diaphragm design. Does anyone know (i) what the IP should be and (ii) how to adjust it. There's a 1 inch diameter cover with a flat slot but I don't know if that's a cover of the tension adjustment. Any advice appreciated. I wasn't able to find a service manual from the usual sites.

Hi Mike.

I have several U S Divers first stages of that era, of various models. You can look at photos of: Aquarius, Calypso IV, and Conshelf as these are the most common U.S. Divers regs from the 1970s, and that should help you tell which you have. The Aquarius (unbalanced piston) and most models of the Conshelf (balanced diaphragm) are externally adjustable by turning a screw. The Calypso is a flow-through piston design; on later models small adjustments are possible using an allen key inserted through the bottom port, and larger adjustments require disassembly and insertion or removal of shims.

IP specifications vary among models, and sometimes a slight deviation from the specified IP is necessary to get the second stage to breathe at its best. Based on the information you've provided, there's no reason to believe that the 125 IP is indicative of a problem.

 

[herman]

Sounds like a Conshelf (see photo above). 127 is a little low but it's not unusual for them to drift a little after service (rubber parts taking a set). 130-135 is the common IP for those regs but it's not really critical as long as it's stable, also 5 psi is well within the realm of your IP gauges being off a little. In any case, you adjust it by turning the slotted screw on the end.

If it does not look like the photo above then it's likely an ealy Aquarius. Its pretty easy to identify one, the yoke is part of the tapered body and the body has several ridges running it's length. It also is adjusted by a wide slotted plug in its end, 130 +/- is also the correct IP.

 

[tech3324]

I've always adjusted my IP with the regulator unpressurized to avoid scoring the HP seat while turning the Adjustment Screw. I assume that's the best way to adjust the Conshelf? @herman

 

[herman]

There is no need on a diaphragm reg to depressurize the reg. The HP seat is isolated from the rotational forces by the diaphragm....you have big time troubles if it turns. The adjuster slides on the spring, the spring slides on the spring pad and the spring pad slides on the diaphragm.....if the rotational forces make it through that and then through to the pin support and pin and still rotates the HP seat you have big time problems.
Adjusting a diaphragm first stage should be done while pressurized and it needs to be cycled between adjustments so any rotational forces that are built up in the spring can work themselves out. It's pretty common for the IP to overshoot a little during adjustment and come back a few psi after it is cycled a time or 2. I adjust it close, cycle the second stage a couple of times, readjust and repeat until the IP holds where I want it. Also, after rebuilding, it 's common for the IP to shift some after the reg has been under pressure and/or has set up for some time due to the rubber components taking a set. It's best if you check and reset the IP after a dive or 2, it should stabilize out at that point and stay good for years after that.

 

[Luis H]

When adjusting the IP I normally go just a bit past what I want it and then just turn the adjustment screw back just a bit. That helps to get rid of the torsion applied to the compression spring during the adjustment process.
Then I basically do the same as Herman mentioned.

 

[PanamaMike]

Does it look like this?

Yes. That's it. The 1" dia slotted thing, that's the tension screw or a cover?