Harbinger One: Circuit is Done. One small issue

[pryde]

Just finshed the harbinger one circuit and got it dialed in very nice so far I think.

At first I was getting very little modulation and the lamp filaments were barely glowing. Luckily I socketed R46 and swapped the 47k for a 4.7K...That was it! More brightness and much more effect ofcourse. Everything else is per the build doc for 9v option. Still messing with gain/ramp but getting some great sounds. I do have to say I am not finding the chorus very appealing but the vibrato is excellent. I pointed the photcells directly at the lamp and made a reflective sheild with a plastic cap that was the right size.

SOCKET R46 !

The issue I am having is the LED function. When jumpered the circuit works great; however, when trying to run an LED there is very little/no effect and the LED light just stays on and does not pulse with the speed control?
Thoughts?

[madbean]

What kind of LED are you using? Is it a water/clear/high brightness type?

If so, try using a plain red diffused (that's what I used).

The LED indicator will not have a terribly strong pulse at slower speeds, but does at high speeds. It's a compromise to make a simple solution for an indicator. If it isn't working for you I'd say leave it off. Or, another possibility is to create a separate circuit that drives the LED (using a transistor). I didn't explore this because of the space limitation on the PCB, but maybe there is something I can come up with as an alternative.

Lastly, you can try running another 4k7 in parallel with the LED (anode to ground). This may pull the LED pulse into a better on/off ramp, but it might have a negative effect on the vibe overall.

[pryde]

Thanks Bean. I tried a number of LEDs (clear bright and diffused) and did not have any luck. They stay lit and there is no pulse at any speed setting.

I will try the parallel resistor idea and report back.

[madbean]

I think you might have something going on then. You definitely should have some pulse to that LED. Hmm.

If you haven't, please double check your values for the resistors on the LFO (everything under the L1 lamp on the schem).

[pryde]

OK, checked all resistor and cap values around LFO and everywhere else while I was at it and everything checks out.

Not sure why there is no LED pulse. THe circuit works great when the pads are jumped but it just looses all effect with an LED? It just stays lit? Maybe there are some voltages I can check on the circuit that may help figure this out? Not sure where to look and what values though.

I will be curious if others have this issue when more get built.