I obtained an Oceanic Datamaster Sport dive computer as part of a package of used dive gear I purchased on eBay. Unfortunately, it would not power up. I assumed the batteries had died, but the screws to the back of the dive computer were covered with lacquer so I assumed that servicing could only be done by an Oceanic technician. A quick Google search verified this, and also let me know that Oceanic was no longer servicing this model. I would have to replace the batteries myself if I wanted to ever see it work.
I found a set of replacement batteries (Sanyo CR14250SE, 3 Volts 850mAh lithium-manganese dioxide) online at Battery Specialists. I placed my order, $15.90 for 2, shipped, and they arrived via first class mail in only 2 days!
Here are the steps I went though in replacing the batteries. I take no responsibility for any damage to equipment, or personal injury that might occur to anyone using equipment used after following these steps.
First you will want to remove the DataMaster from its rubber enclosure. Do this by carefully prying it out through the front, being careful not to disturb what I assume is the pressure sensor on the right-hand side.
Now use a thin flat blade screwdriver to carefully pry the cover off. Be extremely careful not to damage the rubber o-ring seal. If you push the screwdriver in too far you can very easily do damage to the o-ring!
Now put the new batteries in, making sure to match the +/- of the batteries to the markings in the DataMaster. You may need to use your screwdriver to press the contacts out of the way while you insert the batteries.
The power button is in the back cover, so you won’t be able to test it until the back cover is re-installed. Pop the o-ring off and apply some silicone grease to it before slipping it back on. Replace the cover onto the back of the DataMaster and put a couple of screws in to hold it in place.
I don’t have an owners manual or instructions and have been unable to find any online for this dive computer, so if you happen to come across any please email me a pdf or send me a link.