Question on repairing older SP Regs

[Bali1]

I have Mk 5 first stages with 109 and 156 second stages - starting to DIY.

I see SP service kits on eBay for extortionist prices. Are the kits from VDH all I need to perform standard servicing? I know there may be specific part needs which are not included in the annual kits. Thanks.

 

[raftingtigger]

For the MK 5 you need a HP seat and O-rings. VDH is a good place. I buy my o-rings in bulk (10-20 of each) from The O-ring store. You have a multitude of choices in duro and in material. I get my HP seats from VDH.

For the 109 and 156 VDH is the only place to BUY newly made diaphragm covers and exhaust tees. He had them made from silicone. I got impatient before he offered them and made my own diaphragm covers and replacement tees. I will buy any needed further tees from VDH. For more routine overhaul you will need a couple of o-rings, a LP seat (if you have the duro poppet) or a new poppet if you don't. The other option is to make your old style poppet accept a replaceable LP seat. Check out the DIY section for instructions. My method has worked well for me. AWAP makes his own LP seats. Again these are available at VDH.

Tools needed: A curved spanner with IIRC at 1/4" pin for opening the ambient chamber on the MK5, a yoke nut, bullet tool, flat spanner for the HP seat piece, regular wrenches, screwdrivers, hex wrenches as appropriate, a vice (padded) or bolt to hold the 1st stage, lube (Christolube or like), and maybe a pair of pliers. Invest in Harlow's Regulator Maintenance at the very least.

I have converted my fleet of MK5s to DIN by adding SS washer(s) to make the SP universal DIN kit fit. Again, details in the DIY forum.

Good luck.

 

[herman]

A piston oring insertion tool makes life easier.
I make those and several other MK-5/10 tools. If you need or want any specialty tools, drop me a PM and I will send you a catalog.

 

[raftingtigger]

A piston oring insertion tool makes life easier.
I make those and several other MK-5/10 tools. If you need or want any specialty tools, drop me a PM and I will send you a catalog.

Yep, forgot to include that one. I got mine as a bullet tool / O-ring insertion tool.

 

[Bali1]

I see that one of the 156 clamp screws has been badly stripped. What is the best way to replace these? I have seen some older threads on screw sizes - what are the current suggestions? It looks really good on the outside but we will see about the rest.

Herman - already sent PM for you. Thanks again.

 

[redacted]

I see that one of the 156 clamp screws has been badly stripped. What is the best way to replace these? I have seen some older threads on screw sizes - what are the current suggestions? It looks really good on the outside but we will see about the rest.

Herman - already sent PM for you. Thanks again.

If the problem is that the screw is stripped but the threaded clamp is in good shape, the solution is pretty easy. It is a standard threaded screw, #4-40, available in many hardware stores. The head will probably have to be ground down to fit in the recess of the unthreaded clamp, but a Dremel should take care of that. A brass screw is easier to work than the stainless.

If the threads in the threaded clamp are bad, you will need to go up a screw size. For quite some time, the Scubapro service kit for the metal Adj , 109 & 156, included a couple replacement socket head screws that were a bit finer thread and thicker than the 4-40s, so I guess they recognized the problem. (Another reason soaking is required and rinsing is not sufficient.) I don't know the size for tapping but the difference is so small, I'd bet the instruction was just to screw them in. They look to be stainless so I'm sure the would easily cut threads in the brass clamp. If that is what you need, PM me and I'll see what I can find.

If all else fails, I do have a few 4-40 screws (SS) with lock nuts that will work if you cut away some of the excess metal on the clamps. That technique works best with the really ugly metal 2nds.

 

[Bali1]

Thanks for the advice awap. Should I soak in just water at first to try to loosen things up or is some detergent bath indicated?

 

[redacted]

Thanks for the advice awap. Should I soak in just water at first to try to loosen things up or is some detergent bath indicated?

I'm really referring to post salt water dive trips, but a good soak before service if things look a little crusty can't hurt. Soak in fresh water. If things look bad or resist unscrewing, a quick US bath might also help. I have left a stubborn 1st stage soaking in FW for over a week to loosen things up. A few sessions with hot and cold (ice and almost boiling water) can also make a big difference.

 

[Bali1]

Excellent. Sorry to be a bother. I feel like I have something special here and don't want to mess it up so I am more cautious than I probably should be.

 

[agilis]

Excellent. Sorry to be a bother. I feel like I have something special here and don't want to mess it up so I am more cautious than I probably should be.

You do have something special. I have a several Mk5/156 combos, including my first, which I still have 42 years after I bought it with its 109 second stage, the whole package then called a 'Mark V'.

I've updated all of them, from s poppets with the correct longer balance chambers to stainless swivel retainers, and I do all my own work. They are beautiful in every way, form and function.

Take your time and use good tools, especially for first stage O rings. Second stages are a snap, but repeat every sequence over and again until you can do it in your sleep. You develop a delicate feel for them after a while.

I use chopsticks for second stage O rings, and a lighted 20x loupe to check for micro scratches on orifices and other parts. Working on these regulators becomes additive.