Blowing LEDs

[John Price]

I have a DE Star Trek that I recently upgraded to LEDs. Some of these are not working correctly or are burning out or don't work at all. The problem is not specific to any row or column of the lamp matrix and the transistors check out ok. What's going on?

 

[Dave Astill]

are they polarized? cheaper 555 leds have to be inserted in only one position. Also check your switched illumination output voltage and see if its higher than 6.3 volts.