Hi,

This is my first post and I apologize if I'm covering old territory. . .

I have build a true bypass box for all of my effects.  Everything works except for the LED's for any particular effect that I'm switching in.  I'm using a basic 'Boss' style 9V input.  The LED's didn't originally light up, I was able to get them to light up temporarily, but then they seem to burn out.  The worked temporarily when the were connected directly to the 9V source and a basic ground connection.  Can anyone help me with how to get these to work correctly?  I'm using 3PDT switches and I'm obviously doing something wrong, but I'm not smart enough to know what!  Thanks!!!!

Derek

The way I do it is, take a 4k7 series that with the LED, reverse the polarity connections to 9v+ and Gnd. till it lights, adjust resistor [between like 2k and 10k] for LED brightness.
  Break this seriesed LED/R circuit and insert the switch pole and throw connections so they are made in whatever switch mode you prefer...[use 1 switch lug that's inline with the jacks connections and the other unused lug inline with the circuit in and out connections makes the LED on when Effect is on]. You should have one unused lug after connecting the circuit and the LED.
 3PDT's sure make it easy.
 The Marshall Bluesbreaker shows schematic diagram of 3PDT w/LED indicator bypass

Thanks for your help Pete!!!

Did you use resistors between the power supply and the LEDs?  If not, you most likely blew the LEDs.  4k7s are pretty standard.

I apologize for not warning.
 I thought of this last night after shutting 'er down...
 Gotta watch going too low with that LED's limiting R, kwik flashes might not 'get' itm but too much current will blow LED's...
 I remem reading about a 2k there, then later though 4k7 get's most of 'em going pretty good...10k is probably too dim for most.

I use 8k2 resistors for LEDs

Online LED Resistor Calculator:
http://www.luxeonstar.com/resistor-calculator.php

The formula is quite simple:

Resistor Value = (Source Voltage - LED forward voltage) / (desired LED current)

The LED forward voltage of normal LEDs is usually between 2V and 2.5V, for the more exotic ones (blue, white, etc.) it's around 4V. Look at the datasheets for exact values.

But I mostly end up using 10K trimpots anyway :lol:

4k7 is my fav. value.

-Colin

Online LED resistor calculator:

http://www.muzique.com/schem/led.htm

Enjoy!

-Jack

Thanks for everyone's input.  I did blow my original LED's by connecting them directly to a 9V source.  I just got new 3V, 20mA yellow LED's from Radio Shack.  I have built a true bypass box that has 4 LED's with only a 9V power supply.  I've read that you should wire the LED's in series, but I don't have enough voltage to do that (4 x 3 = 12 Volts minimum).  So I'm going to try wiring them in parallel with a resistor for each LED.  Last night I tried a 470k resistor and the LED did not light up, I measure the actual voltage to the LED as 1.55 Volts.  So I'm off to radio shack to get some lower value resistors to try.  By my calculations I'm looking for something in the 300-330k range (9V - 3V / 20mA) = 300k.

Does this sound right?  Will I be okay wiring the LED's in parallel with each LED having it's own resistor?  Is there a better way to do it given my 9V input voltage?

Thanks so much for everyone's help!!!

try 12v automotive leds they aren't actully 12v they just already have a current limiting reistor in them  when you run them at 9v with no current limiting ressitor in them they pull same as my water clear 5mm (12v one is 5mm also) with a 1.5k limiting resistor  which is what i use standard anyway..

Quote from: deke99... By my calculations I'm looking for something in the 300-330k range (9V - 3V / 20mA) = 300k.

That's one "k" too much, make it 300 ohm and things will lighten up! But I would stay way under 20mA current unless you are using a wall wart.

Thanks!  I realized that mistake after using one of the online calculators that someone pointed out.  I have some 330 ohm resistors to try.  I'll post my results tomorrow.

Just wanted to update everyone, I wired my 4 LED's in parallel using 330 ohm resistors and it worked like a charm.  All LED's light up beautifully.

Thanks again for everyones help.  Now that I have a functional true bypass box, my next project will probably be some sort of booster.  I'll look forward to and rely upon more help and guidance.

Derek