I blew my Ophir head.

The way I had my LPM wired is that there's a BNC jack that can double as a signal output for external data logging, or as an input to use as a voltmeter.

Well, long story short, the switch was in LPM mode and I applied 13V into the jack. Ended up blowing the Ophir head circuit inside.

Here it is, output is stuck to one voltage rail.


Decided to poke around and see what went poof. Found out it was only one op amp that got damaged since the other one (the expensive one) had a response when a laser is pointed on the thermopile.


Desoldered the thermopile leads and the board is free.


Using the flood-and-pull method, I was able to easily remove the broken IC


Holes cleaned up without any damaged pads.



I know I will blow it up again in the future so I bought some spares and IC sockets for future use.


And it's back in. op amp is now in a socket so if I ever blow it up again, I just pull it out and slap another in.


And it works. I didn't even have to touch the calibration and offset pots.


While I was at it, I rewired the inside and made a new powersupply.


And added labels so I won't forget which switch does what.


And some warning labels too

*for pics*

Nice job! Normally when something electronic breaks I try to tinker with it, break it more and then concede defeat. One incredibly frustrating thing I have is electronics and physics interest me a lot but I'm not actually very good at grasping physics, electronics theory or math! So while I can look on and observe, actually doing things electrical is both a bad idea and likely to end in disaster for me.

Nothing like saving a broken expensive part and finding that it is fixed with a much much cheaper part! I'm really good at the first part, I have lots of broken stuff, but just need time to fix them!!

trencheel303 said:

Nice job! Normally when something electronic breaks I try to tinker with it, break it more and then concede defeat.

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If the worst case scenario is that you break something that is broken, then you can only gain from tinkering with it. You still will have gained more knowledge about how that piece broke, how it worked, stuff like that.

Plus, you have a new piece to throw in the parts bin!

Great guide I've blown the amp in one of my Ophir heads a couple times as well. I should have put IC sockets in like you did

Very nice repairs! Good call with the labels, we all leave switches in the wrong position some times.

trencheel303 said:

Normally when something electronic breaks I try to tinker with it, break it more and then concede defeat.

Click to expand...

Don't stop tinkering. Conceding defeat is not the right way, you just need to think it through the fixing part before moving forward to make sure what you did won't end up making more mess. We've all been there, I was careless one time and a small broken part ended up blowing up the board traces into soot all over the place haha

BShanahan14rulz said:

Nothing like saving a broken expensive part and finding that it is fixed with a much much cheaper part! I'm really good at the first part, I have lots of broken stuff, but just need time to fix them!!

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Oh yes, the broken op amp was a TL081. the expensive one in the front end was an OP07. I still bought extras for both incase I ever needed it but still only put in a socket on the TL081 since it appears it's the output stage of the circuit which is more prone to blowing.

ARG said:

Great guide I've blown the amp in one of my Ophir heads a couple times as well. I should have put IC sockets in like you did

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I've thought about also adding a socket on the other op amp but since it's doing the front end, it might affect the offset and calibration so I put it off until next time if ever that one blows.

Sigurthr said:

Very nice repairs! Good call with the labels, we all leave switches in the wrong position some times.

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Thanks, seems to make it look better too

This is the best kind of accident to have.
You blew it up then, modded it, and it's a better product now that you
Fixed it.

Nice accident score +1!

Thanks,

I did a bit more work. I had never been able to eliminate noise coming from the old PSU so made this new one and rearranged the wiring, added inductors and ferrite beads in places and was able to lower the noise floor considerably. Readings are much more stable now.

good job on the repair and upgrade!

trencheel303 said:

Nice job! Normally when something electronic breaks I try to tinker with it, break it more and then concede defeat. One incredibly frustrating thing I have is electronics and physics interest me a lot but I'm not actually very good at grasping physics, electronics theory or math! So while I can look on and observe, actually doing things electrical is both a bad idea and likely to end in disaster for me.

Click to expand...

Physics is theory mainly described via mathematics mostly trig and calculus its easier then ya think. But the branch that applies to lasers is quantum mechanics which IS hard to understand.. but building a laser is more about electronics snd d electrical engineering skills. Physics doesnt play and part in the build process

Edit.. of course gravity helps a bit :yh:

xirrious said:

Physics doesnt play and part in the build process

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I see. So it must be "magic" that keeps your project on the table then!

Just kidding, couldn't hold back

Thanks for the pics. I have been wanting to see the preamp board in the Ophir thermopile. Didn't realize it was so simple. That makes me feel a lot better about buying one of these some time soon. I missed out on a great price no eBay a few months ago and have been kicking myself ever since. Great job, BTW.