rhwestfall wrote:Everyone, thanks for the input.
As this is a really early model (2 lp, weak yoke, hp thread is same as lp, integral yoke stem), I'm wondering if Greg Barlow might have some insight as to the possibility of a piston change in the early model to a next generation that is now standard....
I'll update as I find out more.
I would not call that description a really early model. All the Mk-2 and Mk-3 from the 60's , 70's, and into at least the early 80's followed that description. The new yoke retainer didn't come out until much later. I am not sure, but I think it was the early 90's. I am guessing the change came about because of the introduction into the US of the DIN connection.
I started servicing these regulators in 1971 working at Divers Service Center. The regulators that I am most familiar are from that era and some of the earlier ones from the 60’s.
If you post a picture I of the outside I can tell which generation Mk-3 you have. Is the piston cap of your regulator rounded or flat on the bottom? Is the piston head the size of a quarter or a nickle?
The Mk-2 predates the MK-3 by a bit over a year. The MK-2 came out around 1963.
The first generation Mk-3 had a flat bottom and was around from about 1964 to 1971. The second generation came out around 1972 and was around until the early 80's. You probably have a second generation because they are more common. Both had the same yoke and main body configuration (same ports). The main body part number was the 102-7 for both the Mk-2 and the Mk-3.
Below are a couple of diagrams. Notice that the these diagrams have the old part numbers with fewer digits.
If you notice the parts numbering system, the first three digits referred to the regulator where this part was first used. In this case the 102 was because the part was originated in the Mk-2.
Look at the diagrams below and you will see that the seat was the same 102-4.
The Mk-3 diagram below (second generation) only introduced 5 new parts. The new Mk-3 parts all start with the 103 prefix.
I did service some of the first generation Mk-3, but I do not have a diagram for them. As far as I remember and the documentation I remember the only difference between the first and second generation Mk-3 was the piston cap, but not the piston. Note that I am going by memory (but that is also what the Scubapro regulator timeline says). The piston numbering (103-4) doesn't seem to indicate that there was a previous revision (but this is not a sure sign). The first generation Mk-3 were (and are) relatively rare.
Here is a copy of the vintage Mk-2 diagram.
Here is a copy of the Mk-3
