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This small tutorial will show you how to replace the RS-485 chip in an ADI SECU16 Ocelot expansion module. My SECU16 was damaged by a lightning strike/power surge several years ago, but I kept the device around, in case I ever had the time to figure out if it is fixable. I replaced the original Ocelot with a brand new unit, but I never bothered to purchase a new SECU16 since I have other home automation devices which filled the void until recently. I heard that replacing the chip reponsible for the RS-485 communitcations sometimes fixes the situation, so I decided to give it a shot, with great results.
The part in question (SN75176BP) is extremely cheap (<$1 from most sources), it's the shipping and handling cost that will bump up the price a little. Since this chip is also used in the Ocelot itself, and other Ocelot expansion modules, I highly recommend that you purchase a few of them, just in case. Instructions for replacing the chip in the other Ocelot expansion modules are the same.
Before you decide to do this repair, make sure that your SECU16 is enrolled (or at least tried to enroll it). Check the SECU16 manual for more details.
Read more to see the detailed instructions, pictures and video.
The culprit
SN75176BP chip in the ADI Ocelot
SN75176BP chip in the ADI SECU16
Symptoms
My Ocelot was unable to detect the SECU16. Both of the lights on the SECU16 indicated there was a problem. The 'Comms' light would stay on solid, while the 'Active' light would never blink.
Tools & parts required
wrist grounding strap
phillips-head screwdriver
pry tool (I used a small flat-head screwdriver)
new SN75176BP RS-485 chip
Instructions
Make sure you grounded yourself correctly! These are sensitive eletronic components, and a static discharge can damage the component or worse, the entire device. Also make sure you removed the power source.
Use your phillips-head screwdriver to remove the 4 black screws. Once the screws have been removed, you should be able to remove the cover. If you have trouble removing the cover, gently pry it apart with a flat head screwdriver.
Take note of the orientation of the chip! Use your pry tool to gently loosen the chip. Make sure you use pry both sides loose, in several steps. Check the video below if you aren't sure how to do this. Make sure you do not lean on other components with your pry tool, as you could damage them in the process.
Grab your new chip, and set it down on the empty socket. There's a good chance that you might have to bend the pins inwards a little, in order to make it fit. Once you confirmed that the pins are lined up, push the chip down evenly. Make sure the chip's orientation matches the original one.
Replace the cover, and tighten the screws (do NOT overtighten the screws, as it may result in thread damage).
That's it! You might have to re-enroll your SECU16, check your SECU16 manual for more details.
Video
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Conclusion
That's it. Assuming there are no other problems (such as a bad RS-485 chip in your Ocelot), you should be able to communicate with the SECU16 again. This process doesn't take more than 5 minutes, and saves you from having to purchase a new SECU16.
The SN75176BP RS-485 chip can be purchased from many vendors online, but here are the direct links to the most popular ones:
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