How to diagnose a Problem with a broken laser?

[Shady At Best]

Hey everyone.
i built or assembled a purple ish laser about ten years ago with parts bought from members here. I sold it to a buddies kid a few months back and he broke it. I feel sort of bad for him and told him that I would look into the problem. I am pretty sure that he put the batteries in backwards and as I vaguely recall the driver I used had some sort of protection built in it for just the occasion. But I am not sure.
How can I tell if the diode still works and or its the driver? The driver is still getting power..

I think I might have answered my own question.. Put a volt meter in between the driver and diode?
Lets say the driver is bad. How do I find the right driver again? As I sort of recall, the diode was capable of 2+ watts but I had it built at 1.5ish.
I ran through all my old messages here and didnt see anything helpful.
Thanks.

 

[paul1598419]

Ten years ago there were no 405 nm 2 watt lasers available to us here. There are now though. You can use a current limiting power supply to test the LD with. That is what I use. The driver is likely bad if he put the battery(ies) in backwards. You can test that with a dummy load.