Presented as a public service . . .

[Russjstewart]

Hi Ken,
Guess I should have checked your profile before jumping in with gratuitous advice Glad the computer was salvaged. If you don’t mind me asking, what did you use to clean the corrosion off the terminals. I have used vinegar on a cotton swab in the past, then flushed with fresh water, or contact cleaner when I have had it.

Like Dandy Don my track record with electronics and salt water has had its ups and downs

 

[The Chairman]

the o-ring was properly greased and free of debris,

Was the o-ring new, or did you re-use the old one? After two floods, I started changing the tiny o-ring in my VEO250s, DG03s and the other Pelagics I own. I believe it was a "set" in the o-ring that didn't lie in the same way that caused the leak. Even on a radial seal like this one, the o-ring is distorted into an oval during service and may not be perfectly round after disassembly. Any o-ring roll during a subsequently assembly, and you have created a "spiral" due to the old set, sometimes creating enough of a channel that allows water to flow. It may look fine to the human eye, but if everything was cleaned with alcohol and adequately lubed, then that would be my guess. I worked in a P-chem laboratory at UF and often worked with higher than normal vacuums down to 10-4 torr. Seals were tested and re-tested as a $1 o-ring could easily waste $20,000 in time, materials (including LH2) and such. While PDCs are not as expensive, I just don't take chances with used o-rings on battery covers. Now, the battery covers on my Shearwaters provide both radial and axial sealing with little chance of o-ring distortion during assembly. Hmnnnnn, maybe I need to rethink how I handle those as well. I doubt that the price of that o-ring is much more than $0.30.

 

[Ken Kurtis]

Hi Ken,If you don’t mind me asking, what did you use to clean the corrosion off the terminals. I have used vinegar on a cotton swab in the past, then flushed with fresh water, or contact cleaner when I have had it.

Happy to share. Remember, I'm at a resort so not like I have a full shed of tools available. Flushed it with water and scrubbed it out as best I could with my fingers, tissues, and Q-Tips. Then filled compartment with alcohol (rubbing, not Scotch) and let it sit for 5 minutes or so. Then dumped that,. wiped it out again, dried water I couldn't get out with a hair dryer. It didn't totally clean the battery terminals (sping end - negative - was OK) but I could see shiny metal. Popped in a new battery and it fired up, sealed it up and it worked through the dives today (so 2 days). Have not yet opened the back of the computer to see if there's any new leakage going on.

- Ken

 

[Ken Kurtis]

Was the o-ring new, or did you re-use the old one?

Initially we used the old one because it wasn't that old, perhaps 6 months. When she first brought this to me Saturday night, her complaint was it didn't work. When I opened it up, there was NO battery inside. I said, "I think I found the problem." The o-ring to my eye - your point notwithstanding- looked good, was not over-greased, etc., etc. Post-flood (so the last two days), we used a new o-ring. I still think it's the fourth screw but i think there's no real way to know for sure.

- Ken

 

[The Chairman]

Is it a machine thread or more like a wood screw? There are fixes for both kinds of thread. If it's a machine thread, you'll have to epoxy, drill and tap. If it's a tapered cutting thread, then you can still epoxy and drill or you can put a sliver of plastic or copper down there to fill up the void a bit allowing the screw to bite.