"Little Angel" - Super Simple PT2399 Mini Chorus

[EBK]

Felipe,
I really hate to see your bad luck continue with this pedal, especially since your soldering appears to have improved so much since you started this project.

I haven't brushed up on the PT2399 lately, and I don't know for sure what every voltage is supposed to be, but I suspect you have a collection of perfectly fine chips and the problem lies elsewhere (of course, I've warned you before about "problem lies elsewhere" thinking, and I'm not heeding my own advice at the moment  ). 

One thing that caught my eye, and I'm not sure if it makes a difference, is your diode D1.  The spec calls for 1N4148.  Yours looks different from the 4148s I've encountered before....  I'm wondering if just maybe (this is a longshot) you have the wrong sort of diode and that is messing up things with Q1 and pin 6 of the 2399.

[jfrabat]

EBK, thanks for your patience with me, and for the complement of my improving skills!

I am not a huge connoisseur in electronics, but the diode DOES say 41 and then 48 right below it...  My guess is that it is a 4148 (I am assuming the 1N part; it is not written in the diode; there is something, but I cant figure it out), but I am not 100% sure on that.  Here are the pics (by the way, the numbers are TINY!  I had a real hard time checking!  And I was using one that was not installed!).





Here's the symbol (whatever it is) that's above the 41 (looks like a script T or something):



I looked up 1N4148 in Google (images) and found many similar to mine, though, so I am now even more sure that this SHOULD be the right one...

[EBK]

Got it.  Thought your installed one looked darker and had a 0 on it.  Must have just been the lighting.  Oh well. 

[duck_arse]

so, what parts are common to this build and the previous?

[jfrabat]

There is a 4007 on, but thats D2...

[EBK]

There is a 4007 on, but thats D2...

I was just seeing the bottom of the 8 on D1 as a 0.  I can actually make out the "48" now that I've taken another look.  You've got the right part.

[EBK]

I apologize for not taking the time to go back and reread everything you've done so far, but have you tried the following with an audio probe?

1.  Check to see if your dry signal is making it to the 2399 input.
2.  Check to see if you are getting a signal out of the 2399 output.

[jfrabat]

I did, but a while ago.  I'll try it again and see what happens.

[jfrabat]

so, what parts are common to this build and the previous?

Most of them.  Is it time to take them all out and replace them?

[duck_arse]

no. list them, we'll see what we can pick from the list. if you keep getting the same problem with each rebuild using the same parts, logic says it's one of those parts.

[EBK]

no. list them, we'll see what we can pick from the list. if you keep getting the same problem with each rebuild using the same parts, logic says it's one of those parts.

+1

[jfrabat]

You know what, when I ordered the PCB from JMK, I did not receive the PCB in a long while, so they sent me a new one.  Well, it turns out that yesterday the original one arrived.  So one option would be to use the new PCB and start from scratch.  That way I know I am not using the same components as the previous versions! 

By the way, and for the record, I already notified them that I received it yesterday, and Jacob told me to just keep the PCB.  What a great service from these guys!  I truly recommend them, not only because their PCB ROCK (see the picture below), but their service is impecable.



I think I have enough stock to make a new one without having to reuse components.  Now, quick question, though; should I use ceramic disc capacitors again?  Or should I try to find Poly film ones instead? 

[maiko]

Watching this and rooting for you.  I hope you get a working chorus pedal soon.

[EBK]

Now, quick question, though; should I use ceramic disc capacitors again?  Or should I try to find Poly film ones instead?

I would suggest finding film caps, but not necessarily for the reason you might think.  You are about to build this thing for the third(?) time.  Anything that slows you down may also help prevent your muscle memory and/or subconscious secretly repeating a mistake we haven't spotted. 

Sounds weird, but I have to imagine there are dozens of us here (with a nod to maiko chiming in with something remarkably similar to something I too posted way back) that need you to succeed with this project, if for nothing else, to reaffirm that patient persistence and a positive attitude pays off (if you quit, we will all patiently and persistently hold you down and positively force you to keep building this thing -- just kidding  ).

[jfrabat]

I will try to find poly film ones then.  Not sure how easy they are to find in Costa rica, but I will try.  By the way, it is the FOURTH try!  Now, I am nlt sure what's the right adjective for me...  My wife would  probably not call me so much as persistent than hard headed, but one thing is for sure; I tend not to give up (failling pisses me off, and I cant shake that feeling until I succeed, so I keep doing thing until they come out right). 

I will most likely finish my Vulcan Rat first, though.  I had that one working, and the crappi cables I was using kept breaking, so I will do that one again.  I just finished drilling the holes in the PCB I made for that one a few minutes ago (and its the best PCB I have made so far, if I do say so myself!).  But this Little Angel battle is far from over!  I will report back soon!  And thanks to all for the words of support and the technical help!  You guys ROCK!

[jfrabat]

You could be in a position where you cannot have any confidence. Could the PT2399's all be bad? It can happen, depends where you bought them from. It has been known for fakes/rejects to get into the market.
I've found it helpful to set the chip up in a minimal circuit on a breadboard like this...

I forgot values on the in and out caps. These can be 100nF too.
Really only have to connect the signal output to a test amplifier. Simply touching the signal input with, say the tip of a screwdriver, injects noise that comes out obviously time delayed when the delay control is set to maximum resistance. With a continuous test input signal connected, it's hard to tell if there's delay, but turning the delay time control up and down will be heard as pitch shifting.

OK, guys, I revisited the testing circuit.  Remade the whole thing on the breadboard.  When the pot is at 0, sound comes out, but if I turn it up, A LOT of noise comes out and no delay effect.  I am about ready to start construction of the new board (now that I have the EA Tremolo and Vulcan Rat pedals all done, so this one is the only one on the building table as of now; of course, with a board for a phaser, that can rapidly change).  But I am really looking forward to building a Chorus and a Delay (which I think are musts), and the Chorus is the one that has so far beaten me (but that will NOT be the end result!). 

Anyway, back to the testing circuit, I tried replacing the PT and the Pot, but the result is still the same.  I want to be sure the PT I use on the new board is sound, so I want to attack this problem first.  Any ideas?  By the way, the circuit is exactly as above, with the exception of the Pot being 50K instead of 47K.

[EBK]

I was happy to see you get other stuff to work.  Now we can lay to rest the theory that your soldering iron shoots lightning bolts through whatever it touches.   

How many PT2399s do you have?
Did you find new caps?

[jfrabat]

I have about 10 from 3 sources (including Small Bear).  I have not yet looked for the caps, though.

[EBK]

Are you at least using new (non-recycled) caps for this?

[jfrabat]

Are you at least using new (non-recycled) caps for this?

Yes and no, the old pedal is still built, but these are the same caps I had on the breadboard before.  I have enough to replace them, but I figured what are the odds of these caps and the ones in the pedal being all bad, right?.  I will not take it apart so as not to reuse any part.