Figured out why my crashed Eggtimer TRS doesn't work...


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Jul 8, 2014
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I crashed my Eggtimer TRS during my first L2 attempt. Wouldn't fire deployment charges after that. Used it as a backup flight recorder, and for that it worked.

I had Connor assemble the TRS for me at the time because I didn't have the soldering skills. I've come a long way in troubleshooting electronics and soldering since my crash, and I finally decided to take a stab at figuring out the problem.

I thought for sure it was the transistors, so I desoldered them to test them out of circuit. They were fine. What the hell? Back to the board and I found this:

Optoisolators are completely mashed over. I suspect that one of the rivets in the AV bay hit it on the way by. Pulled the traces off of the board. Damn. Now I have to buy a new one.


Owner, Eggtimer Rocketry
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Feb 3, 2012
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Those MOCD217 optoisolators are relatively fragile due to their high profile, I've seen the leads break off at the body of the part. We've gone to a different (and more expensive) part that's pretty much normal SOIC profile, there have been very few optoisolator issues since then.