"Little Angel" - Super Simple PT2399 Mini Chorus

[jfrabat]

I did not leave the pedal onas long as I did yesterday, so I am not 100% sure, but it did get warm.

[bluebunny]

There's no reason for it to get warm, other than locking up.  Do check out the parts connected to pin 6.  Did you try lifting the 100R resistor (I think Jim suggested this earlier)?  It should definitely stay cold with only the 2K2 connecting it to ground.

[jfrabat]

R22 (100R) and R20 (to break the dry feed from the output) are disconnected.  Just to clarify, it is not getting hot in any way, shape or form; it is just slightly warm (normal temperature for any IC).  It is not COLD, but it is not hot.  But there is no signal getting through (with the dry feed disconnected). 

Tomorrow (I can't work on it tonight) I will go through it once more.  Maybe use the Audio Probe to see where the sound is going out...  Not sure still what I should do.  But definitely, the problem is in the wet signal.  The dry signal is working just fine (well, it was before I pulled R20!).

Now, I know it is not the PT (or at least, not ONLY the PT) because I tried with a fresh one.

Pin #	Freq.Ctrl. V	Felipe V	Felipe NEW PT V
Pin 1	5V	5.03V	5.03V
Pin 2	2.38V to 2.42V	2.50V	2.50V
Pin 3	0V	0V	0V
Pin 4	0V	0V	0V
Pin 5	2.75V	1.95V	2.45V
Pin 6	0.61V	2.43V	2.43V
Pin 7	0.88V	0.311V	0.641V
Pin 8	0.88V	0.496V	0.816V
Pin 9 to 16	2.41 (slight movement)	2.51V (starts higher)	2.51V (starts higher)

Obviously the problem is coming from PIN 6.  I also do not get oscillation in PIN 2 (I put the final reading, but it does move when I connect the reader for the first time).

[jfrabat]

Well, on to Plan C...  I just got my JMK PCB for the little angel.  Gonna use it for the third try.  Third time's the charm, right?   At least I got to improve my soldering skills with the prior tries!



Is it me, or it ALMOST looks A LITTLE better than my homemade PCB?

[anotherjim]

The moment of truth? Breath is bated.

[bluebunny]

Is it me, or it ALMOST looks A LITTLE better than my homemade PCB?

You can hardly tell the difference...   

[jfrabat]

Hey, guys, could what I was experiencing be due to using 10 nF instead of 100 nF capacitors in 2 places?  Building Plan C, I noticed I had more 103 caps than what I used in the new build and 2 104 caps missing.  Could this the the reason it was not working?  I do not know which caps were wrong, as I had already taken out the ones off the previous board... 

By the way, the board is coming along nicely.  My soldering skills are also improving (I feel this PCB is easier to solder than the home made ones; maybe the double side thing?  Or maybe the new temperature controlled Weller iron?).

AND THE AWARD FOR THE MOST IMPROVEMENT IN SOLDERING IN 2016 GOES TO...





Anyway, this is where we are at as of tonight.  Tomorrow I have to buy some ceramic 104 caps (only got poly ones, and they do not fit well in the PCB), and attach the pots and leads and then is off to sound test!

Speaking of capacitors, what is the main difference between ceramic and Poly?  When should I use which?

Oh, and I am missing one resistor, and I need help figuring this out.  In the build manual it says R2 is CLR.  What the heck does that even mean?  All the others have values...

[EBK]

Speaking of capacitors, what is the main difference between ceramic and Poly?  When should I use which?

Oh, and I am missing one resistor, and I need help figuring this out.  In the build manual it says R2 is CLR.  What the heck does that even mean?  All the others have values...

Another thread where I gave my take on caps: http://www.diystompboxes.com/smfforum/index.php?topic=116096.msg1074164#msg1074164

CLR is a Current Limiting Resistor for an LED.  Value is generally not critical.  Try 4.7k, perhaps if your circuit doesn't specify.

[anotherjim]

There are often 4x 100n (or about that value) around the PT2399. I and I'm sure many others have experimented with the values. I think having lower values makes the sound noisier & grittier. I don't recall it causing total failure.

Probably too late to suggest leaving out the pin 6 100R and the dry feed mix resistor (different part numbering on this pcb?).

[jfrabat]

There are often 4x 100n (or about that value) around the PT2399. I and I'm sure many others have experimented with the values. I think having lower values makes the sound noisier & grittier. I don't recall it causing total failure.

Probably too late to suggest leaving out the pin 6 100R and the dry feed mix resistor (different part numbering on this pcb?).

I can always desolder them.  Do you think its worth a shot?  It's not like I can finish the board without the missing caps, which I need to get later on.

Another thread where I gave my take on caps: http://www.diystompboxes.com/smfforum/index.php?topic=116096.msg1074164#msg1074164

CLR is a Current Limiting Resistor for an LED.  Value is generally not critical.  Try 4.7k, perhaps if your circuit doesn't specify.

Oh, OK.  I do have a 4.7k already next to the LED.  Which brings another interesting subject up; all my grounds are connected in the wiring, but the PCB has grounds for the DC jack, switch LED and Audio jack.  I only have one ground coming in.  I should use the DC jack one, right?  Or is it better to undo what I have and wore everytbing to the PCB?  Similarly, the LED is wired directly to the sqitch with its own resistor.

[jfrabat]

One more question; in the schematics, the pots only use pins 2 & 3 (well, I always assumed "n/c" stood for "not connected; I could be wrong!) but here they are connecting all of them to the PCB.  Should I wire them up?

[EBK]

N/C is "not connected".  Generally, however, we would tie that extra pin 1 to pin 2.  Won't change anything though.

As far as grounding goes, there and endless opinions on the topic.  There are definitely some wrong ways to ground things, but otherwise there is a wide murky swamp of "proper" and "good enough". I personally prefer tying all my grounds to the DC jack rather than to the PCB, but I tend to shy away from telling others they should do the same. Should sound the same either way. 

But, if you say something like "ground is ground -- they are all the same," you risk being burned at the stake.   

[jfrabat]

One more question; in the schematics, the pots only use pins 2 & 3 (well, I always assumed "n/c" stood for "not connected; I could be wrong!) but here they are connecting all of them to the PCB.  Should I wire them up?

After further inspection, it looks like Pin 1 of both pots are not going anywhere on the PCB (the square pads).  I'll just leave them disconnected.

[bluebunny]

If you're board-mounting your pots, then solder all three connections for a little extra mechanical strength.

If you're connecting via wires, you might in any case want to connect the unused lug on the pot to the middle wiper lug as insurance against the wiper connection going bad.

[jfrabat]

The boards are wire mounted.  I will put in the jumper if I get UN-frustrated!  Just finished wiring everything up, put in a fresh PT, and still, no chorus.  Only the dry signal is getting through!  HELP!!!!That's 3 strikes for me already!

Voltages at PT:

Pin #	Freq.Ctrl. V	Felipe V	Comment
Pin 1	5V	5.01V	OK
Pin 2	2.38V to 2.42V	2.51V	A little high; is it an issue?
Pin 3	0V	0V	OK
Pin 4	0V	0V	OK
Pin 5	2.75V	2.12V	A little low; is it an issue?
Pin 6	0.61V	2.43V	THIS IS AN ISSUE!
Pin 7	0.88V	0.864V	OK
Pin 8	0.88V	0.868V	OK
Pin 9 to 16	2.41 (slight movement)	2.51V (starts higher)	I think this is OK, right?/td]

Obviously the problem is still coming from PIN 6.  I also still do not get oscillation in PIN 2 (I put the final reading, but it does move when I connect the reader for the first time).

Another thing to note is that PIN 1 on the OpAmp is not oscillating.  The second OpAmp is, though (pins 6-8).  Also, no heat from PT, so that's an improvement.  What do I check now?  The pots?  I am a bit stumped!

[EBK]

You could look at this as great news.  It suggests that your homemade board is probably good if you are having the same problem with the fancy one.

I know you've played around with different chips.   Have you tried replacing any caps?  I assume you recycled these from your other board.

[jfrabat]

You could look at this as great news.  It suggests that your homemade board is probably good if you are having the same problem with the fancy one.

I know you've played around with different chips.   Have you tried replacing any caps?  I assume you recycled these from your other board.

Some of them, yeah...  But the store was out of 104 ceramic caps.  Only had 2 left, which is exactly how many I needed to finish the pedal.  I have 104 poly caps, but they are bigger than what fits on the board.  That's why I used the small yellow ones and the 2 ceramic ones (which were not yet in the picture).  I have enough to swap them all out, but stuffing them in will take some creativity...



Here you can see the small sized 104 caps I used.  I have 2 ceramic ones in the 2 empty slots above the PT.  The poly ones I have are a little bit bigger than the green 332 that's also above the PT.  The electrolitic caps I can replace with the exception of the 100uF (I think I am out of those).  Should I replace the caps?  Is there a way to test them?

The other thing I have not replaced are the pots.  And the pot quality here is not the best; I already had issues with the pots before.  I may just start with that and see how it goes.  Would bad pots give me this issue?  Is there a way to test them as well?  They are easier to replace than the capacitors...

[anotherjim]

Bad pots would stop the LFO from working. If the speed pot is bad, it won't oscillate. If the depth pot is bad, it won't get through to pin2 of the 2399.

[anotherjim]

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.

[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.

I built the circuit, but I get no sound at all out of it...  2 different PT's.  I'm guessing that's pointing to my problem?