Smallclone pulse indicator LED problem

Started by liddokun, May 03, 2008, 08:19:32 PM

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liddokun

I tried attaching an LED to pin 1 of the LM358 in my Smallclone.  I get the LED pulse, however it's very faint, very hard to see.  While screwing around with the cable, i accidentally touched it to pin 7 of the LM358, and I got a very bright pulsing.  I looked at the pinout, and pin 1 is output A, and pin 7 is output B.  Why is the pulse on output A so much fainter than on output B (pin 7).  Also, is there a way to have the pulsing turn off when the pedal is bypassed?
Thanks
To those about to rock, we salute you.

mdh

I don't really know the implications of sinking current from the LFO to make a flashing indicator, but... the reason that the flashing is stronger on pin 7 is that the LFO is made up of 2 stages.  The first one (which happens to be IC2b in this layout) is a square wave, banging back and forth between a low voltage and a high voltage (IIRC the swing in the Small Clone is something like 7V).  The second stage (IC2a) smooths the square wave out into something more closely approximating a sine wave.  It doesn't spend as much time at high voltages, so you get a dimmer flash.

Regarding your second question, if you're using a 3PDT, couldn't you just wire it so that the LED is connected to ground when the effect is active, and not when in bypass?

liddokun

I've never actually wired with a 3PDT before, I've always used DPDT in all my boxes.  How do I wire it so that its connected to ground when it's active? Do you have a diagram?  So the positive end goes to the LFO, and the negative goes to?
And is it ok to have the LED hooked up to pin 7? Because the LED is too dim on pin 1 for it to be useful.
Cheers
To those about to rock, we salute you.

mdh

You would wire it like this, except that where the +9V is connected to the switch, you would connect ground, and you would flip the LED around so that the cathode (negative end) is connected to the switch.  I would also put a current-limiting resistor in there either between the switch and the LED or the board and the LED.

As I said before, though, I don't know what effect drawing current from the LFO for the LED would have on the behavior of the circuit.  I guess you could just try it with and without the LED, and see if you notice a difference.

liddokun

My smallclone is a reissue, so I dont believe it's true bypass.  It's got 3  cables running to the board: one to in, one to out, and one to a resistor labeled: footswitch.  I think this is the buffer?   It's not wired like in the diagram.  How do I rewire it first? Can I just skip the part of the circuit that says "footswitch" and wire directly like the diagram?  I'll post picture as soon as I can.
To those about to rock, we salute you.

mdh

Ah, I thought you were dealing with a DIY version.  I don't have any experience with the real thing, so I can't really advise you on how to wire in this mod.  Have you searched to see if/how others have done this?

sfx1999

You might need to use a FET to amplify/buffer the signal so that the LED doesn't alter the output of the LFO. Something like this with a 10K resistor. It might need some tweaking though.