LED Light Bulb Failure

[Nick]

The LED elements in my failed lamps were arranged in a series parallel arrangement and appeared to run off 12V. I applied 10V to them and it was extremely bright.

Small and obvious point - LEDs are current, not voltage devices - once there is enough PD across then to conduct, they need current limiting - connecting a bunch of LEDs across a 12V supply (assuming there's only a few of them) will cause them to burn very brightly indeed, but not for long...