# LED getting power but not lighting up



## sticky1138 (May 11, 2022)

I built the Promethium and it works fine, but the LED doesn't light up.

It switches on and off as expected, the continuity seems good on all of the off-board wiring, and the LED is getting 9V according to the multimeter. I tested a few different LEDs to see if I had a bad one, including different orientations. Nothing. Any ideas? I'm stumped because it's getting power.


----------



## giovanni (May 11, 2022)

Pictures would help!


----------



## sticky1138 (May 11, 2022)

This same exact problem is actually happening to me with the Dung Beetle I have going as well. Here are pics of each:

Promethium










Dung Beetle









I have the LEDs alligator clipped (and the DC jack on the Beetle) because I was switching them around a lot, but I can confirm there is continuity and it's the same problem as before, when they were soldered in.

The Promethium's LED solder pads are on their last leg from soldering and desoldering so much, so I'm nervous I'll have another problem on my hands if they burn out, but they are still making a proper connection at this time.


----------



## zgrav (May 11, 2022)

try touching another led to the legs on the one on the board to see if it lights up.  if it does not, try reversing the leads on the LED and touching the LED leads on the board to see if it lights up.  the first test lets you see if your LED on the board might be dead, and the second lets you see if you might have the LED in backwards.


----------



## sticky1138 (May 11, 2022)

Yes, I did try that on both without results


----------



## giovanni (May 11, 2022)

Did you test continuity between LED, CLR, Vcc and ground (check the schematic for exactly what I mean)?


----------



## Bio77 (May 11, 2022)

Do you have a diode tester on you DMM?  You can use this to check that your LEDs are functioning.


----------



## zgrav (May 11, 2022)

giovanni said:


> Did you test continuity between LED, CLR, Vcc and ground (check the schematic for exactly what I mean)?


measure the voltage on the two leads of the LED when you think it is supposed to be on.  anything?


----------



## BuddytheReow (May 12, 2022)

If the LED has power and there's continuity to the board you've probably installed a bad LED. Swap it out and it should work just fine.


----------



## sticky1138 (May 20, 2022)

giovanni said:


> Did you test continuity between LED, CLR, Vcc and ground (check the schematic for exactly what I mean)?



Connectivity is good on these, but I don't see CLR on the schematic, what is this?

Voltage is 9V on leg, 0 on the other.

I've tested a dozen different LEDs, no luck yet.


Should the LED be getting power when the pedal is switched off? Because it is


----------



## BuddytheReow (May 20, 2022)

In bypass mode there is still power going to the diode. The ground connection is severed via the footswitch which is why you won’t see it light up. The current has no return path


----------



## Betty Wont (May 20, 2022)

sticky1138 said:


> Connectivity is good on these, but I don't see CLR on the schematic, what is this?


The CLR is R100 on the Dung and R37 on the Promethium.


----------



## sticky1138 (Jun 13, 2022)

I think I might have burnt off the soldering pads on both trying to troubleshoot. Is there a quick and easy way to rig up an offboard LED, maybe one that connects to the 3PDT breakout board with a resistor?


----------



## BuddytheReow (Jun 13, 2022)

To the breakout board? No.

The good news is that you can connect a wire to + power and attach a CLR then to the diode. The cathode can get wired to the breakout board where 'SW' goes. You're merely bypassing the PCB to get the led to work.


----------



## sticky1138 (Jun 14, 2022)

BuddytheReow said:


> To the breakout board? No.
> 
> The good news is that you can connect a wire to + power and attach a CLR then to the diode. The cathode can get wired to the breakout board where 'SW' goes. You're merely bypassing the PCB to get the led to work.



Thanks for the tip, that's exactly what I was looking for!

I wired them both up using this technique and now they work fine. I still have no idea what the problem was before, but I'm glad they're up and running.


----------

