Problems with salvaged leds on project to convert ATX power supply to bench power supply

Thread Starter

Ukulele man

Joined Oct 15, 2018
I salvaged some green red and white 3mm LEDs from an old Audio mixing desk to use in the project. On testing with a coin cell all the coloured LEDs lit but not the white ones. They were not desoldered but cut off at the base of the pins so no thermal damage. Can anyone please advise me why they don’t light up.