Help Identifying USD EARLY First Stage and Parts

[BigSwell]

I have what I believe is a early year USD single hose first stage that I can't ID. It has 1 3/8" HP port and 2 LP 3/8" ports. When I opened it up I found it in near perfect condition in internally. However I noticed the main spring for IP adjustment is actually 2 springs (one that is skinny and one that is similar to the Conshelf, the skinny spring sits INSIDE the fat spring). Then I opened the HP side and found a square HP seat which looks similar to the Mistral however it isn't as long and the center is not indented like the Mistral for the pin. Does anyone know what model first stage this is, and most importantly what HP seat I should be looking for as a replacement? The diaphragm appears to be the same as the Conshelf, there is no spring block like the Conshelfs have however. Attached pictures.

[luis]

That is anon-balanced diaphragm regulator.

It is not US Divers. I am believe it is a DACOR, but I am not sure the model number.

I just checked a couple of catalogs, Dacor Olympic Model 200. The pictures and description (including: "Dual spring design eliminates vibration"), and "Teflon coated high pressure seat", all seem to match your pictures and description.

It came out in 1969 and it is still shown in the latest catalog (PDF copy) I have in 1978.

[BigSwell]

Thanks Luis, that really helps. The reason I thought it was a USD first stage is it had a USD Cousteau-Gagnan "hydro-lung" second stage attached. Both are in excellent condition so I'll rebuild them. Any idea if I can get a replacement HP seat for the first stage somewhere? If not I wonder if I can put a USD Conshelf crown block in with springs a new longer pin with the USD HP seat, I guess if that works that it would be a balanced first stage.

[luis]

No, that would not make it a balanced first stage, Not even close.

The inside barrel on a Conshelf has a lip specifically designed to support and lock the balancing chamber. Without that lip the pressure thrust on the back of the balancing chamber will just push on the seat. Totally disabling the balancing chamber function.

The volcano orifice of a non-balanced regulator is also a different diameter than in a balanced diaphragm regulator. There is a reason for that. The explanation is not complicated, but I would recommend reading Regulator Savvy Book, by Pete Wolfinger.
https://www.scubatools.com/c-23-regulat ... -book.aspx
https://www.scubatools.com/p-603-regula ... bound.aspx

Regulators look simple and are very simple, but there is a bit design that goes on the sizing of the components.

I would not be mixing components from totally different regulator designs unless they are the same dimensions or you understand the pneumatic function and the consequences of the changes. Keep in mind that just because something looks like it works, it may not work in all conditions.


Does the seat really need to be replace? You may be able to polish the surface.

Good luck

[BigSwell]

Thanks again Luis, as always you have provided great info.