Old Vintage Yoke?

[g1138]

I recently won a Scubapro Mk5 + 109 combo on ebay and I can't for the life of me figure out how to take off the dust cap.
Hopefully the pictures explain my predicament.
There's no yoke screw or place for it at all. So I'm wondering two things:
1) How do I remove the dust cap
2) How does this first stage seal up with the tank.

I can't depress the yoke connection, not sure if it's corroded shut or not. There some brine deposits on the 109 Diaphragm so I wouldn't be surprised if the first stage is sticky as well.

Anyone ever seen this before?

 

[Fishpie]

It's a MK6.....basically a MK5 with a pneumatic yoke.
It has a spring that needs to be pushed down.
The bit that seals against the o ring needs to be pushed towards the body of the reg.

 

[g1138]

Ah, that would explain it. Thank you.

I wish Scubapro had a retired page on their website to help identify these old models.

So, at least I know for sure that it is in fact pneumatic. However, I can't depress the pneumatic at all. It seems real stiff.
Do you need to remove the dust cap to take the reg apart? There's no hex for me to fit a wrench over to take the reg apart.

 

[herman]

Hold the dust can in one hand and the reg with the other. Unless it's corroded shut you should be able to push the dustcap down toward the reg then angle it out. The air inlet moves, not the yoke. If it's too stiff, you can gently pry the dustcap with a screwdriver. Insert it in the gap at the SMALL end of the dustcap and pry the cap away from the yoke (you can see the tank alignment pin between the yoke and the small end of the dustcap).

 

[Luis H]

I own a couple of Mk-6 (for display only) and sold several of them working at a Scubapro shop back in the 70's.

In this design the yoke pulls back. There is a strong spring that pulls the yoke close until the air pressure locks it in place.
It is a strong spring, but you should be able to pull it back. Try twisting it first to loosen up any corrosion.

In that design it is not the air inlet that moves.

I can post a diagram later.

 

[g1138]

I'll try to pry it when I get back from work today. It wasn't moving for me.

It's too bad being pneumatic though, I was planning on using it for a stage bottle.
I'll probably tinker with it just to see how the parts work.

Unless anyone wants to trade for a Mk2?

 

[scubadada]

g1138,

The MK6 is on the Scubapro regulator history timeline SCUBAPRO - Looks like you have the intial version, 2nd could have the pneumatic yoke replaced with a standard yoke. Sounds like you still have a great 2nd stage

 

[g1138]

g1138,

The MK6 is on the Scubapro regulator history timeline SCUBAPRO - Looks like you have the intial version, 2nd could have the pneumatic yoke replaced with a standard yoke. Sounds like you still have a great 2nd stage

Perfect, they do have a way to look these things up. And yes, I still have yet to pop open the 109, but I'm happy to own my 3rd one. Those regs are great!

 

[scubadada]

Perfect, they do have a way to look these things up. And yes, I still have yet to pop open the 109, but I'm happy to own my 3rd one. Those regs are great!

I have a MK5/109 I bought as my 1st regulator in 1972. I had the yoke upgraded and added the 4 LP turret. It performs beautifully.

 

[Couv]

I'll try to pry it when I get back from work today. It wasn't moving for me.

It's too bad being pneumatic though, I was planning on using it for a stage bottle.
I'll probably tinker with it just to see how the parts work.

Unless anyone wants to trade for a Mk2?

Please don't pry on it. As Luis mentioned there is a spring in the yoke assembly that pulls the yoke closed. Then pneumatic pressure cinches it. If pulling on the yoke and regulator body don't release the dust cap, try a good soak in hot soapy water. If you need more muscle, pass a line through the yoke and then pull on the regulator body. The yoke also has a screw type adjustment so it can be mounted it on different valve thicknesses. Just hold the body and turn the yoke.

As for diving it-well, that's a different story. A while back we had a discussion here: http://www.scubaboard.com/forums/vintage-equipment-diving/454171-can-you-identify-first-stage.html

If you decide not to dive it as it, you can always remove the pneumatic yoke and replace it with a MK 5 yoke assembly.