https://photos.app.goo.gl/uvCcjPKxAGWq4bYp7
https://photos.app.goo.gl/TocfivaPxdCanJ2j6
https://photos.app.goo.gl/NdosVScU6nWYRMeg9
https://photos.app.goo.gl/SzuzEVVBNtV4suBH6
Hello!
This is my first pedal build(I know, I probably should have started with something simpler) and I could use some help diagnosing what's wrong with it. When I turn the effect on the LED turns on but no signal is passing through. Perhaps a fresh set of eyes might be able to spot a mistake I'm not seeing. Let me know if I can provide more photos to help out, I tried to give angles that would allow easy comparison with the vero schematic but some components are still a little hidden. I have an audio probe and multimeter for fault finding but I'm not sure where to begin, I found points on the circuit where I could tell the pots were affecting the signal but none of those points really sounded like delay. What sort of things should I be checking for to be certain the IC's are working as expected? What kind of information can I provide to get better assistance on here? I need some help building up my skills in this area, any guidance you can provide would be appreciated. If possible I'd like to find someone locally that could assist me when I hit roadblocks but I'm not sure how or where to find someone who possesses the skills. I'm a programmer from Albany, OR. If you're close by and interested in meeting at some point, hit me up, I've got a lot of musician friends in the area but I could desperately use more friends with a passion for electronics.
There is definitely something to be said for starting simple :P My first pedal had a total of 7 components and still took me a month to debug ::)
Anyway, first thing I see: jumpers should be on top for vero builds. Obviously it's impossible to tell from a picture if the jumpers are shorting anything, but I could definitely see it happening when you're using bare metal jumpers on vero.
Quote from: HighSolstice on November 08, 2019, 02:59:01 PM
What sort of things should I be checking for to be certain the IC's are working as expected? What kind of information can I provide to get better assistance on here?
I can answer both questions at the same time: VOLTAGE. Get us the voltage on each pin of both ICs, that will tell us a lot.
Summary: move your jumpers to the top of the board, get us voltages. We'll help you get it figured out! 8)
Quote from: vigilante397 on November 08, 2019, 05:24:17 PM
I can answer both questions at the same time: VOLTAGE. Get us the voltage on each pin of both ICs, that will tell us a lot.
Summary: move your jumpers to the top of the board, get us voltages. We'll help you get it figured out! 8)
+1. Voltages help, and jumpers *definitely* should be on the top of the board. On the bottom is just asking for trouble!
Good work so far, and don't worry - there's lots of people here who can help you get it sorted out. Good luck!
I'll take your advice on the jumpers into consideration on my future builds. I'm not sure how easy it would be to desolder them now so I'll probably leave them for now if I can avoid it. Here's the readings I got from the ICs.
Base voltage reading: 9.30V
TL072:
Pin 1 - 8.73V
Pin 2 - 8.70V
Pin 3 - 8.70V
Pin 4 - 9.22V
Pin 5 - 9.18V
Pin 6 - 8.82V
Pin 7 - 9.22V
Pin 8 - 8.90V
PT2399:
Pin 1 - 9.18V
Pin 2 - 9.22V
Pin 3 - 9.22V
Pin 4 - 9.22V
Pin 5 - 8.72V
Pin 6 - 9.19V
Pin 7 - 8.74V
Pin 8 - 8.74V
Pin 9 - 8.72V
Pin 10 - 8.74V
Pin 11 - 8.75V
Pin 12 - 8.74V
Pin 13 - 8.75V
Pin 14 - 8.71V
Pin 15 - 8.70V
Pin 16 - 8.75V
Wow. I'm sorry, but almost none of those are what they should be. I'll start with the TL072 though. Common expected voltages are
Pin 1 - 4.5V
Pin 2 - 4.5V
Pin 3 - 4.5V
Pin 4 - 0V
Pin 5 - 4.5V
Pin 6 - 4.5V
Pin 7 - 4.5V
Pin 8 - 9V
Nothing on the PT2399 should be above 5V because there should be a 5V regulator feeding that. But since you have positive voltage on every pin of everything that means you have ground and your 9V rail shorted somewhere, so your regulator wouldn't be doing anything anyway. So on that note, where are you placing the negative probe of the multimeter to measure these?
Quote from: HighSolstice on November 13, 2019, 01:36:04 AM
Here's the readings I got from the ICs.
Check your ground connection(s).
I kept my negative lead clipped to the ground terminal on the back of the 9V input jack.
In that case, check the ground to the board actually connects up properly.
Try with the power off checking the continuity of various points that are supposed to be Ground, including back to that ground terminal input. They should all buzz..and if they don't you've got a problem that might explain why everything is reading much too high.
Sorry, I should have been clearer. Do what Tom said. (Thanks, Tom.)
I fixed a grounding issue in my off board wiring. Now it is passing a clean signal through. Here are my updated readings, they still don't exactly mirror those expected results.
TL072:
Pin 1 - 1.61V
Pin 2 - 1.36V
Pin 3 - 3.68V
Pin 4 - 0V
Pin 5 - 4.46V
Pin 6 - 5.19V
Pin 7 - 9.03V
Pin 8 - .61V
PT2399:
Pin 1 - 4.9V
Pin 2 - 2.4V
Pin 3 - 0V
Pin 4 - 0V
Pin 5 - 3.58V
Pin 6 - 2.42V
Pin 7 - 0.49V
Pin 8 - 0.74V
Pin 9 - 2.36V
Pin 10 - 2.41V
Pin 11 - 2.41V
Pin 12 - 2.42V
Pin 13 - 2.41V
Pin 14 - 2.40V
Pin 15 - 2.41V
Pin 16 - 2.41V
The PT2399 looks OK, but that 072 is still weird. You have no power on the power pin (#8), but plenty on pin 7! Having looked at the back-of-the-board pics, I would seriously revisit those subterranean links and move them top-side: there's just too much scope for shorts.
Nobody said anything about the absence of IC sockets.. :icon_cool:
as the blue one says - yer links. there is one on the far right-top, 5 columns in, looking on the component side, should be 4 tracks down, yours is 5 tracks down. I stopped looking then.
Doh! You're right! I've looked this over soooo many times and hadn't noticed that. I'll fix this tonight and report back. Gonna have to look over all the surrounding components again too. I've got an assortment of socket sizes in the mail for my future builds but I got excited and started this build before I had the chance to order them. Learning a ton as I go, thanks for everyone's help! Out of curiosity, how did you come up with those expected values? Is that something I could obtain simply by looking over the TL072 datasheet or is that found by use of Ohm's and Kirchoff's laws? These are the things I'm interested in learning early on so I can become more self sufficient. I've taken a couple electronics courses in the past and vaguely remember using those laws but that was nearly a decade ago now and I may need to brush myself up on the mathematic side of things if it'll help me out here.
After fixing that link placement I'm closer to the expected values but still a couple off on the TL072 and it's no longer passing a signal.
TL072:
Pin 1 - 4.70V
Pin 2 - 4.48V
Pin 3 - 3.68V
Pin 4 - 0V
Pin 5 - 4.46V
Pin 6 - 6V
Pin 7 - 7.1V
Pin 8 - 9V
Quote from: HighSolstice on November 15, 2019, 05:39:33 PM
Out of curiosity, how did you come up with those expected values? Is that something I could obtain simply by looking over the TL072 datasheet or is that found by use of Ohm's and Kirchoff's laws?
Not really, those just come from knowing how op-amps work and from using them in dozens of builds before. It doesn't matter what build it is, TL072 voltages are going to be pretty well the same (unless you're using a bipolar power supply, but they will still be predictable).
Good to know, I'm getting regular readings around 4.5V on pin 6 of the TL072 now. I'm still getting readings around 7V on Pin 7 and I'm still not getting any output.
As a slight diversion, and following from Nathan's reply, check this video out. You will emerge the other side enlightened!
https://youtu.be/7FYHt5XviKc
it might be a good idea to turf that IC and replace it with any other dual opamp you have at hand. oh, no sockets, is that right?
I have output and I can send the circuit into oscillation using the knobs now but my guitar has no effect on the delay. I was able to play along to drone sounds a bit which was neat.
I took a break from working on this build for a bit and knocked out an EQD Acapulco Gold and a Switchable 9v/18v power box with sag controls. Due to my efforts here, those took me no time at all to complete and worked without a hitch. I'm still not sure why I can get the oscillations going but my guitar signal has no delay on it. I received those sockets just yesterday so I might try to remove the TL072 and replace it with a new socketed one.
I've socketed the TL072 and tried a few of them and got the same readings so I'm back to looking at the surrounding components, still puzzled by this one.
well we've turned the page now, so we've forgotten everything you told us. and you've made changes. so, new photos of your board please, and a new round of voltage measures. please. perhaps also restate the current problem, no guitar? no delay?
https://www.dropbox.com/sh/7jgt7fmpa2wxef6/AABKjvxBM4P4Jto8xbu9OmUza?dl=0
Base Reading: 9.17V
TL072:
1 - 4.41V
2 - 4.41V
3 - 3.62V
4 - 0V
5 - 4.39V
6 - 4.21V
7 - 7.58V
8 - 8.88V
PT2399:
1 - 4.89V
2 - 2.40V
3 - 0V
4 - 0V
5 - 3.97V
6 - 2.40V
7 - 3.44V
8 - 3.48V
9 - 2.41V
10 - 2.40V
11 - 2.41V
12 - 2.41V
13 - 2.39V
14 - 2.38V
15 - 2.40V
16 - 2.40V
Here are some updated photos and readings. Currently I can hear my dry signal through the pedal whether the footswitch is engaged or not. The delay can be driven into oscillation independently of your clean signal by turning the pots and this is also heard whether the effect is on or off. The only obvious effect turning it off seems to have is turning the led on/off. I fried a bit of the track while I was was moving that link so it's been moved two slots to the right as can be seen in the photos, shouldn't be a problem based on the layout. I've shown the switch and wires attached to the board in case any of that seems problematic as well. This has me thinking I should build a test box to make this simpler in the future.
pin 7 of the TL072 should be about 4V3, yours is way high. find where the wrong connection is thereabouts.
I found the problem, I had also burned the track off a bit where that red arrow is pointing. I added a link between the green dots and now the voltage on Pin 7 is measuring 4.48V but I am still experiencing the same results when I tested it out.
(https://i.postimg.cc/34G5XYkg/CF85-EE77-F14-D-4-D5-D-8-AE9-BA2-BEC0-B6-C04.jpg) (https://postimg.cc/34G5XYkg)
well that's some progress. I tried to understand the description of the "tails" but I'm afraid it makes little to no sense to me without a real live circuit diagram. perhaps - if you un-tails your build back to the standard version, it will dis/prove the basic build, maybe point to the tails-ing.
I tried it again yesterday and I actually heard delay coming from my guitar but it still doesn't seem to behave exactly as intended. If I get the delay into self-oscillation it takes a while tweaking the knobs back into a sweet spot before I can get the delay sound to come back on my guitar. I'm not sure what might cause this.