LED Comes On, Then Goes Out?.

[zombiwoof]

Hi, I have a couple of Zoom PD-01 Power Drive pedals (nice clean OD/boost pedal that doesn't color the tone), and on one of them the LED comes on at first when you switch the effect on, but it goes out after a minute or so.  The effect continues to work fine, it's just the LED that doesn't stay on.  What could cause this, just a bad LED?.  What should I look for to fix this?.

Thanks,
Al

[R.G.]

LED are really simple. Forward current = light; no forward current = dark.

Unless the LED is really damaged by overcurrent and/or overheating, it's what's driving it, not the LED. And in general, the driving circuit has a current limiting resistor, in which case it usually doesn't get damaged.

I don't know what's inside the PD, but the name "Zoom" is associated with "digital effects" in my head. If they did something clever like using the current limits of one output pin of a logic chip to limit the LED current, maybe the LED was damaged by it, but replacing the LED will just let the next LED get hurt.

Is the going-off sudden or a gradual fade? That could help distinguish dying LED from something like a cracked solder joint on an SMD limiting resistor.

[zombiwoof]

LED are really simple. Forward current = light; no forward current = dark.

Unless the LED is really damaged by overcurrent and/or overheating, it's what's driving it, not the LED. And in general, the driving circuit has a current limiting resistor, in which case it usually doesn't get damaged.

I don't know what's inside the PD, but the name "Zoom" is associated with "digital effects" in my head. If they did something clever like using the current limits of one output pin of a logic chip to limit the LED current, maybe the LED was damaged by it, but replacing the LED will just let the next LED get hurt.

Is the going-off sudden or a gradual fade? That could help distinguish dying LED from something like a cracked solder joint on an SMD limiting resistor.

This is an analog pedal, AFAIK.  It has a good reputation as a very transparent OD, and is often compared to the Klon.
I will have to plug it in and watch the LED and see if it fades or suddenly cuts off, I have only used it a couple of times, and both times I was playing, and all of a sudden noticed the LED was off, even though the effect was still working.
Maybe I can find a schematic for it, or if someone here has a sdhematic maybe they could post it so you could see the circuit.
I have a second one that works fine, I bought them because of their reputation on the forums, and got good deals on both.

Thanks,
Al

[R.G.]

This is an analog pedal, AFAIK.  It has a good reputation as a very transparent OD, and is often compared to the Klon.
I will have to plug it in and watch the LED and see if it fades or suddenly cuts off, I have only used it a couple of times, and both times I was playing, and all of a sudden noticed the LED was off, even though the effect was still working.
Maybe I can find a schematic for it, or if someone here has a sdhematic maybe they could post it so you could see the circuit.

Ah. OK, watch for how it cuts off. Analog will be easier to trouble shoot.