Why did my diodes die?

[Grix]

So I was building a laser for a customer, using a m140 diode and a DIY mohgasm linear round driver in a C2 host. But when I finished and tested the laser, the output was way too low, and when unfocused the laser output was a bunch of lines instead of an uniform circle.

I thought there were something wrong with my driver, maybe a short somewhere, but when I disassembled the laser and probed it with my multimeter, looking for a fault, I found nothing. The driver seemed perfectly normal, and the it outputted the correct current. So I thought maybe the diode was DOA, and I wired up another diode to the driver. But the same thing happened again. And hen I turned the laser on and off again the output had decreased even more, it was clear that the driver was frying the diodes.
I finally changed the diode and this time also the driver and now it was working.

While I'm pretty pissed about losing $120 in a flash, the most annoying thing is that I have no way of learning from my mistake because I still have no idea what I did wrong, the driver acts like any other driver, and I am certain it was not static electricity from my fingers or anything that killed both diodes.. So what I'm asking is: Do any of you have an idea about what could be wrong with my build? How can I properly troubleshoot a mohgasm linear driver?

 

[Eudaimonium]

So far everything points to the faulty driver...

I guess it's a bit of a stretch to assume you have an osciloscope to check out the output?

Sounds like a big spike at startup, followed by the normal current output you'd expect. What's it output capacitor looks like, possibly b0rked?

 

[Cyparagon]

It's relatively common for something to short to the case when you assemble it. I've had this happen a few times with flashlights. Nothing works when assembled. Take it apart, and it starts working again.

 

[benmwv]

Its possible the regulator is damaged. If you want to send it to me I can scope it and see whats up.

 

[Kookapeli]

The same happened to me too

 

[Photonz]

sounds like a real pain. id go with cyparagon's advice

 

[ryansoh3]

Does your multimeter have a min/max readout?

I'm sure you've tried this if you had the feature but perhaps you can see if there is a brief spike when the driver is powered?

 

[Meatball]

This is all great advice. I'm betting the problem is very small.