Help needed on rat-2 mod

[mattdavios]

I did my rat-2 mod successfully and i am very satisfied with it. However, i had a minor problem...I wanted to change my Rat-2 Led to a 5mm blue LED. After installation of the 5mm blue LED, it didnt light up. I tried change directions and it didnt work. Do i need to change the resistor value somewhere? I just did a test on the LED and it's working. I really dont know what went wrong  Really appreciate if anyone can help me out with it. Thanks a lot for all your helps

[petemoore]

  If you have a standard LED and ~4k7 resistor, you can easily make a 9vdc 'tester' which can substitute for the suspected one.
  or/and test for 9V where it's supposed to be, and ground.

[mattdavios]

its kinda deep for me to understand...can you elaborate more on it please?

[Meanderthal]

Doesn't the Rat2 use a version of the millennium bypass? If so it might not be cooperating with the change. The blue diode might have a different forward voltage than the circuit wants. Just a thought...

[mattdavios]

is there any way to find out what resistor value i will need?

[tonefreak]

is there any way to find out what resistor value i will need?

There are a ton of LED resistor calculators on the internet... here's one:

http://www.hebeiltd.com.cn/?p=zz.led.resistor.calculator