Changing O-Rings on a Perdix...

[noj3333]

I need to change my o-rings out on my Perdix. It’s actually a job I’m fearing.

That being said I have a few questions…

I need to lube up the new o-rings?

If I do need to lube them up, use a VERY minimal about of lube, correct? I like the idea of putting a small dab between my thumb and pointer finger and gently ‘massage’ the o-ring in that lube? You just want the o-ring coated, but not ‘caked’ in globs of grease, correct?

Can I use Trident silicone grease? If not what should I use, Tribolube? I plan on using factory Nitrile O-rings, the blue one’s that come with the computer.

Lastly, when putting the new o-rings on, you stretch them from the side opposite the threads, over the ‘end’ of the cap, opposite the electrical contact, until they set in their groove? I’m trying to think of another way of saying this… you DO NOT put them on over the threaded section of the cap?

Thank you for any advice or tips… messing this up can flood a great computer…

 

[rsingler]

You've got it.
Right about the grease amount.
Silicone or Tribolube is fine.
I can't remember if my Perdix manual specifies a lube. You should confirm.
But I always use Tribolube.
As for fitting the oring, stretching over the cap avoids the thread, but risks really stretching just before you're trying to make a seal. With the Perdix cap, the diameter isn't so big that it'll make a difference. With other things, and with firmer o-rings, you risk splitting the oring. In this case you should be fine.
An alternative method is to place the oring on the narrow threaded portion, and use your thumb nail to slip it into position by running the nail in the groove of the thread. That way, the oring gently slips over the threads one at a time.
Since the seal is (in this case) at the sides and outside edge of the oring, any scuffing of the inner side shouldn't matter.
Two more things:
1) Use a plastic dental tooth cleaner (the kind that come in a bag with an inch of floss in them) to remove the previous oring. That way you won't score the plastic cap.
2) REALLY IMPORTANT: Inspect carefully under bright light for dust, hair, filament after you fit the lubed oring. Stuff that's just invisibly floating in the air loves to cling to the lube, and represents a tiny water channel into your battery compartment.

Don't worry. You'll do just fine!

 

[NorCalDM]

First do they really need to be changed they are static so unless the cap has been removed and installed multiple times I would think they are fine or are the cut. O-rings will take a set after awhile but that takes quite a bit of time. I use Christo Lube and yes use very little of it also make sure the o-ring is not rolled or twisted in the groove that will shorten the life of the o-ring.

 

[outofofficebrb]

I"m raising this thread from the dead because Shearwater customer service recommends Christolube for their nitrile o-rings. There are so many variants (e.g., MCGXXX). Does it matter which one? Is there one that is better than the other?

Thanks.

 

[rsingler]

MCG-111
Other MCG-xxx can be VERY different.

But I use Tribolube-71

 

[outofofficebrb]

MCG-111
Other MCG-xxx can be VERY different.

But I use Tribolube-71

Sorry for the dense and possibly ignorant question...what is the primary difference and is one better than the other? Thanks!

 

[rsingler]

My opinion only:
I use Tribolube because I've found that it doesn't dry over time. Irrelevant for your computer, since you'll be changing batteries yearly, if not more often.

But in servicing regs, I commonly see a dry Christolube paste in regs that have sat for three years, and it's very difficult to remove. Tribolube doesn't do that. They're both Mil-spec and compatible with oxygen, so no preference there.

But Christolube is the 800-pound gorilla with a much larger market share. I just happen to disagree, after working with both for years. They feel different on the fingertips, too.

If you take a lump of Christolube and hit it with a propane torch, it'll sit there, and eventually a residual tiny bit will hold a glow.
Do the same thing with Tribolube-77, and it just turns gray and does not become even a tiny ember. I don't know if that matters, but a guy I really respect showed me that about six years ago.

 

[Searcaigh]

I have been using Sea&Sea O-ring lube on my Petrel 2 and Perdix for the past few years as it's what I have at hand usually.