ShortScale.org

Hello there you knowledgable types.

My question is, can you wire an LED the wrong way round? The LEDs I have have a short and a long leg. The pedal I want to wire it into has a black and a red wire. Do I need to worry about this? Or just wire them up however I like?

Background: My original POG has a busted LED. I ordered it from GAK in 2007, and I had to wait for something like a month while they ordered it from America, so I got it, plugged it in, and the LED flickered and just died. Which was disappointing, but the pedal never stopped working (even after I literally poured an entire beer on it) so I just ignored it. I finally decided I wanted to fix it though, so here I am.

Okay, I did some basic research (hooray for google!) and the "long" side of the LED legs is the positive side. So... which of the black and red wires will be positive? I'm guessing red?

Probably, but can you follow the wire back to the board and see if it can be worked out that way?

Hurb wrote: ↑Tue Jan 03, 2023 1:08 pm Probably, but can you follow the wire back to the board and see if it can be worked out that way?

Yeah, the board doesn't say shit. Just has a circle around it saying "LED 7" and that's it.

Tried to take pics of the solder points in case there are clues I'm not seeing.

I'm probably going to guess that the red is positive. How likely am I going to blow the pedal up if I'm wrong?

Is that not a "-" between the circle and where it says C60?

Oh it does look like it. Fucking eagle eyes, just couldn't make that out in real life at all. Thanks Paul.

Well, I just need to dig out my shrink wrap tubing and then I'll solder it up and try switching it on.

Also, I've just read that different coloured LEDs require different resistors in the chain... I'm replacing a red LED with a blue LED, which apparently has a higher resistance. Is this something that the underlying circuitry of the POG will just deal with? Will the LED circuit be a parallel circuit that doesn't negatively affect other aspects of the overall circuitry of the pedal?

Hmmm, first I'd ever heard of that. I always assumed that you used whatever colour you liked best.

Without knowing anything about electronics, I'd imagine that the resistance will just determine how brightly it lights up.

Differently coloured LEDs do differ in resistance and hence in current they produce due to the fact that they need to emit completely different wavelengths of light. I think a Turbo Rat has LED clipping diodes instead of silicon ones and it's a fairly common mod to play with the colour of the LEDs to get nastier or vice versa smoother sounds to a point where people have figured different combinations where they use mismatched colours of the LEDs

There's also the "apparent brightness" of different colors, often you want a higher resistance for blues and greens than you do with reds. The circuit should be fine, I think what you mean by "parallel circuit" is that the LED is normally not the same path that the rest of the circuit is on, so it shouldn't affect the rest of the pedal. Usually the LED is powered straight off the power supply and the switch.

There will already be a resistor in there for the old LED, but that blue will likely be fucking blinding with that resistance. You can just wrap another resistor onto either leg of the LED, then run your wire to the leg of the resistor, for one of the legs. That should add some series resistance. This will be in addition to the resistor already present, so you won't need a value that high.

Usually, I breadboard different LEDS and use a trim pot to determine the resistance I want based on the brightness. You could examine the datasheet for that LED, but I'm not sure what part it is. If anything else, you could start with just adding a 1k resistor and see how that suits you. If it's still too bright, up it to 5-10k.

Disco Rat

KC and the Sunshine LED

Pedals with bright as fuck LEDS sound cooler though,

I bought a bunch of LEDs that said they were already "diffuse" so if it does end up blindingly overpowered, hopefully the diffuse nature of the bulb will temper it a little.

I mean, I've made mistakes with things like this before, so I'm also entirely prepared to have to avoid ever standing directly over the pedal ever again while it's switched on in case my corneas get burned out.

They’re perfect if you’re covering Blinded by the Light.

Diffuse means the light doesn't shoot straight out like a beam of piss. It likely will just make it omni-directional blinding.

Do you guys not have resistors in the UK?

They do but unfortunately they’re manufactured by Lucas and are the size of a toaster.

Resistors are futile

So I wired up the LED. Initially, I'd just snipped the existing LED off and stripped the ends of the wires for the new one. As I was soldering the second wire, the positive wire snapped at the solder joint on the PCB.... I was NOT equipped to do a desolder job so I did what anyone in my position would do: just dived in anyway. I basically succeeded in fistfucking the solder connection to the board into infinity, and in my rush to finish up, I kind of managed to lay a big blob of solder ACROSS the positive AND negative holes on the PCB.

Job royally fucked, I thought I'd leave it there until I could find my solder sucker, but then I noticed I'd also managed to pull the negative wire for the power supply socket off the board too. I was a bit more careful with that one.

So, after galloping around like a fucking... idiot on the guts of a £300 pedal, I plugged it in.

The result is that the pedal itself still worked absolutely fine, but.. the LED doesn't work. I'm probably just going to leave it alone now...