Poison apple. help me think through what I am seeing

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Diynot

Well-known member
So my Poison Apple “works”, but I am getting serious popping/thumping at the envelope opening and even a little distortion on lower strings/frets. I have been pouring over this thing doing all the troubleshooting basics and the thing I keep coming back to is that my 5v keeps disappearing. So long story shorter, a continuity test between the + terminal of the power jack and the pads of the regulator beeps on both the left and middle pads, but not the far right. IMG_5742.jpeg
This would seem to indicate that the left pad is meant for the Vin. Great except the pinout for the regulator has the left pin as Vout.
IMG_5743.jpeg
IMG_5744.jpeg
And I do get continuity between the anode side of D4 and the left regulator pad. So should I just ignore the silkscreen and flip the regulator? then my question becomes why does the middle pad show continuity to the positive terminal, shouldn’t that be connected to ground (which it actually does show connection to both🤔)? Also get continuity between the left pad and the collectors of the bc550. One other oddity is that I do not get Vcc on ANY of the pads😭 Help a brain dead brother out please.
 
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jwin615 said:
L78Lxx and L78xx have reversed pinout. Power the board up without the regulator and see which pin is hot.
If you have 9v on the center pin, you have a bridge/short somewhere
Click to expand...
The regulator I am using is the one pictured so I’m going with there may be a short. In desperation I have off boarded the regulator on a vero and fed it into the left pad of the regulator and every thing seems to be behaving. It’s what I get for taking a build break.
 
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Well, the popping/thumping is resolved but I am still getting light distortion on the E string and some of the higher frets of the A. Sounds a bit like fret buzz, but it happens with multiple guitars (Humbucker and single coil) and is gone when I turn the pedal off. Going to audio probe some other day since I am tired of looking at this. Posting pics in case someone else wants to put eyes on it. IMG_5728.jpeg IMG_5739.jpeg IMG_5740.jpeg
As per my previous post, the regulator has been off boarded so disregard that in the pics
 
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Try different op amps for that light distortion. The TL072's you have look sus

The middle pin of the L78L05 is supposed to be ground. If you are getting continuity between pin 1 and 2, then your 5v supply is shorting to ground somewhere. Check anywhere that 5v is present, like Q2, Q3, and the bias pot, and downstream of these, for any stray solder or broken/bridged trace, leads not trimmed short enough etc that could cause this
 
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falco_femoralis said:
Try different op amps for that light distortion. The TL072's you have look
Click to expand...
Thanks for taking a peak at my problem child. So I have tried 2 different sets of lm358 as well as the TL072 which came from Mouser so would trust to be reliable. All with the same issue. I somehow must have borked the regulator section of the board. Off boarding the regulator solved the thumping issue. Entirely possible I’ve F’d something else up somehow causing the distortion. Meh
 
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