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PostPosted: Sun May 16, 2021 1:25 pm 
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Joined: Sat Jun 01, 2019 6:01 pm
Posts: 182
Location: Surprise, AZ
This may be how the pedal is supposed to act but after initial engagement, the effect becomes very subtle after a few seconds.

It's as if the depth decreases on it's own.

All controls function properly, zero issues with the build other than this.
My initial thought was a dying battery so I plugged it in and the same thing happens.

Fwiw, I am using a Purple LED. I've read that different color LED's may affect this build.

Any ideas?

Thanks,
~Troy

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PostPosted: Sun May 16, 2021 5:00 pm 
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Joined: Mon Nov 23, 2020 1:39 pm
Posts: 181
Location: Vermont
I built one a few weeks ago, with a clear blue LED, and I thought I noticed the same thing but attributed it to "listener error." I've just now listened again and ... it is subtle but it does seem to be as you describe.

I also notice that the LED is faintly illuminated when the effect is switched out; upon out-switching it is sort of faint and then it gets still fainter as time goes by. I've scrutinized the schematic and I only see paths to ground through the LED through capacitors, so maybe one is leaky? I doubted Q3 (FET) would let much through, but turning the DEPTH knob down (CCW) does make it fainter, so that must be a clue of some sort. Does it mean C5 (electrolytic) is leaky?

There is a thread here somewhere describing some of the subtleties of this design and after reading I thought I'd try to see how much the LED choice would affect it. I clipped a green, then a red, LED across the blue LED to see how much difference it would make (those have lower V_forward so would be the dominant current path). I wasn't convinced that I heard any huge difference. Maybe when work slows down next month I can put it on the 'scope to see if my eyes see what I think our ears hear. Maybe it was to do with C5 eventually acquiring its average charge; ignoring the R12 branch, the RC constant for (VR1+R10)(C5) would be 11 seconds, right?


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PostPosted: Sun May 16, 2021 5:24 pm 
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Joined: Sat Jun 01, 2019 6:01 pm
Posts: 182
Location: Surprise, AZ
WMP1 wrote:
I built one a few weeks ago, with a clear blue LED, and I thought I noticed the same thing but attributed it to "listener error." I've just now listened again and ... it is subtle but it does seem to be as you describe.

I also notice that the LED is faintly illuminated when the effect is switched out; upon out-switching it is sort of faint and then it gets still fainter as time goes by. I've scrutinized the schematic and I only see paths to ground through the LED through capacitors, so maybe one is leaky? I doubted Q3 (FET) would let much through, but turning the DEPTH knob down (CCW) does make it fainter, so that must be a clue of some sort. Does it mean C5 (electrolytic) is leaky?

There is a thread here somewhere describing some of the subtleties of this design and after reading I thought I'd try to see how much the LED choice would affect it. I clipped a green, then a red, LED across the blue LED to see how much difference it would make (those have lower V_forward so would be the dominant current path). I wasn't convinced that I heard any huge difference. Maybe when work slows down next month I can put it on the 'scope to see if my eyes see what I think our ears hear. Maybe it was to do with C5 eventually acquiring its average charge; ignoring the R12 branch, the RC constant for (VR1+R10)(C5) would be 11 seconds, right?


Cap bleed was another of my thoughts too, but im ignorant when it comes to electronics...i just learn as i go...lol

But yep sure, 11 seconds is about right.


I have some other LED's i can try too.
Will report back tomorrow evening.

Thanks,
~Troy


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PostPosted: Sun May 16, 2021 10:41 pm 
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Joined: Wed Apr 26, 2006 5:14 pm
Posts: 8659
Location: Truckee, CA
We always recommend reverting any mods to stock when issues arise. This is one of those few pedals where changing the led color can change the performance of the pedal. It’s because supply voltage goes through the led on its way to the LFO.

I’ve gigged one of these pedals for a lot of years. You shouldn’t have any change in trem intensity after a few seconds, nor should your led be dimly lit in bypass.


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PostPosted: Mon May 17, 2021 9:02 am 
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Joined: Sat Jun 01, 2019 6:01 pm
Posts: 182
Location: Surprise, AZ
Morgan wrote:
We always recommend reverting any mods to stock when issues arise. This is one of those few pedals where changing the led color can change the performance of the pedal. It’s because supply voltage goes through the led on its way to the LFO.

I’ve gigged one of these pedals for a lot of years. You shouldn’t have any change in trem intensity after a few seconds, nor should your led be dimly lit in bypass.


Sent from my iPad using Tapatalk


When bypassed, the LED is off.

I will install a Red LED tonight and report back.
No other mods have been done to the pedal aside from that.

Thanks,
~Troy


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PostPosted: Mon May 17, 2021 6:56 pm 
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Joined: Sat Jun 01, 2019 6:01 pm
Posts: 182
Location: Surprise, AZ
Problem solved!
It was in fact the Purple LED causing the issue.
I put a Red one in and all is well!

It has to do with the difference in Forward Voltages.
Learned something new today!

Moderator, feel free to add RESOLVED to the title of this thread.

Thanks,
~Troy


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