Aion FX Luna Tremolo (Tremulus Lune Clone) - Depth Knob Not Working

[werm42]

Documentation: https://aionfx.com/project/luna-optical-tremolo/

Schematic: (see attached)

What's it doing: When the Depth knob is all the way down — the signal is silenced (like a second volume pedal). It seems the knob current works to attenuate the maximus of the waveform rather than amplifying the minimus.

What's it supposed to do: The documentation states that "With the depth knob turned all the way down, the pedal will act like a boost pedal", which to me would indicate that the Depth knob should neutralize the waveform.

It's a 1kB pot, I've tested the pot itself (while soldered into the board) — it's showing reasonable values on all 3 lugs with the knob swept in either direction.

Your help is appreciated!

W

[werm42]

IC Voltage Values:

TL072:

1: 5.85v
2: 5.97v
3: 6.20v
4: 0.00v
5: 5.88v
6: 4.57v
7: 4.55v
8: 9.1v

TL022:

1: 4.54v
2: 4.54v
3: 4.53v
4: 0.00v
5: 4.52v
6: 4.53v
7: 4.52v
8: 9.08v

[iainpunk]

what is the resistance reading you get over the vactrol resistor side? with the depth down, both with and without power applied to the circuit
i suspect 330R R13

we'd also like pictures of your board, both component and solder side.

cheers, Iain

[11-90-an]

^^^what Iain said.. 

I especially echo pictures of the your board....  might just be a short or burned component somewhere.

Also, welcome to the forum... (Iain.... not again... )

[PRR]

Are you using a healthy RED type LED? White LED voltage drop is too high for this plan.

Voltages around the LED part, depth swept, seems like a next step.

However there's realy not much enforcing "With the depth knob turned all the way down, the pedal will act like a boost pedal". It could be infinite boost, no boost, or a loss. Too many trends have to align to make that promise come true.

[iainpunk]

Also, welcome to the forum... (Iain.... not again... )

owh, $hit, welcome to the forum, dude

[werm42]

what is the resistance reading you get over the vactrol resistor side? with the depth down, both with and without power applied to the circuit
i suspect 330R R13

we'd also like pictures of your board, both component and solder side.

cheers, Iain

Vactrol resistor side? -> I'm unclear on how to check this as the vactrol has 2 leads that tie into 2 different resistors. Could you explain it to me like I'm 5? Which leads do you want me to test where?

Photo of component side (would need to take the whole thing apart for solder side).

[iainpunk]

measure the resistance of the legs on the side that does NOT say LED. both with the power on and off, with the mix all the way down.
it is done by setting the multi meter on the ohm setting and putting both probes against the leads on the inner side of the circuit board.

cheers, Iain

[werm42]

measure the resistance of the legs on the side that does NOT say LED. both with the power on and off, with the mix all the way down.
it is done by setting the multi meter on the ohm setting and putting both probes against the leads on the inner side of the circuit board.

cheers, Iain

Power On / Depth 100%:
Negative Side Vactrol Resistance: 19.8k (oscilates, probably cuz modulation)

Power On / Depth 0%:
Negative Side Vactrol Resistance: 1.8M


Power Off / Depth 100%:
Negative Side Vactrol Resistance: NaN

Power Off / Depth 0%:
Negative Side Vactrol Resistance: NaN

[werm42]

measure the resistance of the legs on the side that does NOT say LED. both with the power on and off, with the mix all the way down.
it is done by setting the multi meter on the ohm setting and putting both probes against the leads on the inner side of the circuit board.

cheers, Iain

I'm an idiot — you didn't mean to remove the power source, you meant to turn the switch off?

Switch On / Depth 100%:
Negative Side Vactrol Resistance: 20k (oscilates, probably cuz modulation)

Switch On / Depth 0%:
Negative Side Vactrol Resistance: 1.2MΩ

Switch Off / Depth 100%:
Negative Side Vactrol Resistance: 19KΩ

Switch Off / Depth 0%:
Negative Side Vactrol Resistance: 1.1MΩ

[iainpunk]

i actually meant the power off, you did good. i wanted the resistance if the LED was fully off, the NaN tells me the LED isn't fully off when the pedal is silent, but not in bypass.

does it reach full volume when its just used as a tremolo?
i guess that a possible solution would be to ensure the current to the LED is high enough to keep it lit, maybe try changing the R14 1k (parallel to the LED) so there is a higher voltage on the LED and it keeps current flowing, i suggest using 5.6k to begin with and going higher if its still too low a volume.

cheers, Iain

[werm42]

i actually meant the power off, you did good. i wanted the resistance if the LED was fully off, the NaN tells me the LED isn't fully off when the pedal is silent, but not in bypass.

does it reach full volume when its just used as a tremolo?
i guess that a possible solution would be to ensure the current to the LED is high enough to keep it lit, maybe try changing the R14 1k (parallel to the LED) so there is a higher voltage on the LED and it keeps current flowing, i suggest using 5.6k to begin with and going higher if its still too low a volume.

cheers, Iain

Does it reach full volume? - yes, with all the other knobs at 100% the depth at 100% is at full volume. The depth at 0% is like 5% volume (almost silent).

Sorry, NaN in this case would mean that the resistance is so high — it's immeasurable (with power removed). Wouldn't that mean the pedal is working?

Increasing R14 from 1k to 5.6k — you're telling me to increase the resistance to ground as a means of keeping voltage in the circuit — do I understand that correctly?

This is a pre-designed circuit sold 100's of times over, shouldn't these values be "vetted"? I haven't changed any of the values (I just built from what was provided).

[werm42]

What's it supposed to do?: Smooth out the waveform to a constant tone

What's it doing now?: Attenuating the signal.

[PRR]

....Sorry, NaN in this case would mean that the resistance is so high — it's immeasurable (with power removed). Wouldn't that mean the pedal is working?....

Look at the signal path. The LDR is in *series* with the path. If it is infinite, signal can't get through. If it is 1Meg, signal is about 1/20th, signal is real darn weak.

This rig expects an idle-glow in the LED. I'm not sure what controls that.

[werm42]

R13 (330R) is showing a resistance value of 3.3kΩ?!?!

That can't be right?!

[werm42]

I replace that 330R resistor, everything works fine now.

When I desoldered the resistor fell in two pieces on my bench so clearly that was the problem. 

[iainpunk]

I replace that 330R resistor, everything works fine now.

When I decided the resistor fell in two pieces on my bench so clearly that was the problem. 

hahaha, happens to everyone, even people with multiple years of experience.
i'm glad to hear its working

cheers, Iain

[werm42]

I replace that 330R resistor, everything works fine now.

When I decided the resistor fell in two pieces on my bench so clearly that was the problem. 

hahaha, happens to everyone, even people with multiple years of experience.
i'm glad to hear its working

cheers, Iain

The problem with this kit is that all the resistors have an extra layer of coating on them (with the resistance values printed on them).  This extra layer of coating make it challenging to bend the leads to align with the mounting holes. This 330R was the first one I mounted, and I admittedly had to force it a bit to get the leads through the holes. 

[duck_arse]

I thought those were extra high quality brand resistors. are you saying they have a coating over a blue body? good sleuthing, too.

[werm42]

I thought those were extra high quality brand resistors. are you saying they have a coating over a blue body? good sleuthing, too.

The body of the 330R got a bit scratched, there was a blue-body underneath. While I appreciate the resistance being written on body, I'm not sure if reading those tiny numbers are harder/easier to read than understand which color is which with the stripes? 

Here's the solder side of the board, any feedback about my proficiency is appreciated.