Tonepad CE-2 debug

[Fuzzy-Train]

Thanks... Francisco or Matt?... whichever posted.

I guess I won't be needing that electro cap jlullo...

While desoledring and soldering many times I accidently lifeted a pad... but it was a graound pad and luckily it was right next to another ground pad so I just extended the lead of that resistor and bridged it to the other ground. That wouldn't cause any problems would it?? I circled that part in one of the photos.

You sure it would just be the LFO IC that's faulty? Cause I'm going to try and get another TL072, and I wonder if I should get replacements for all the IC's just in case. Also, other then heat, what could make an IC stop working?

I tested my pots, and although one measured 90k they both funtion like they're supposed to.

All my wiring was right. It's kind of hard to mess up wiring with the silkscreened board, but I checked again and it all looks right.

I tested  the voltage of R35 while rotating the depth pot and here's what I got: The lead going to the jumper = 3.22 to (as I rotated it) 3.49 and the lead to the pot = 4.02 to 4.37
I also did this to R32 and got: Lead to pot = 4.41 to 4.42 and the lead going to C19 = 2.54 to 4.11. What all this means I don't know LOL, but maybe someone can make something of it.

Here are some pics:
(some parts of the board look scratched up because I was cleaning the flux off, but I didn't damage anything while doing that)

[Fuzzy-Train]

Well, I just tried it with a NE5532P chip from my Rebote 2.5 (the Rebote actually calls for a TL072 so it has the same pin out) and it's still doing the same thing... high pitched oscillation squeal that's controlled by the rate pot, and it goes higher and lower depending on which way I turn it.

Could it be that the dots on my IC's are not in the same place as the layout... If I knew more about IC's I'd switch them around to see if it makes it work, but I'm afraid of damaging them.

Anybody?

[Fp-www.Tonepad.com]

they seem to be in the right orientation.

Did you check the oscilating voltage (voltage reading, black probe to ground, red probe to...) the output of the LFO.

I asked you to...

You can try an audio probe and listen for signal at R13 and C10. (research on what an audio probe is if you don't know)

If you have an analog multimeter you should be able to see the oscilation produced by the lfo (measuring volts at r35 for example), with a DMM it's harder to see but you can if you turn the lfo speed really slow. (black probe to GROUND, red probe to R35)

That info would really help.

[Auke Haarsma]

Not to hijack this thread...but I've build the CE-2 on breadboard and have about the same voltage readings as posted in this topic. Those seem ok to me.

But here's the problem:
-I get a distorted, delayed sound (this is a matter of setting the trimpot, if I understand correctly)
-and, more importantly, I get a pitched constant tone with a pulsing swirl to it. It does respond to the rate pot and depth pot. Could anyone point me where to look for the cause of this noise? There's no chorussing going on btw.

I have oscilliating voltages at the lfo, so that seems ok.

I made one mistake...instead of connecting IC4 pin 8 to ground I put it to 9v... corrected that, but I don't know if that could have caused any damage.

[Andre]

and, more importantly, I get a pitched constant tone with a pulsing swirl to it. It does respond to the rate pot and depth pot. Could anyone point me where to look for the cause of this noise? There's no chorussing going on btw.

It seems like your BBD clock frequency is to low (within audible range).
That's the constant tone with pulsing swirl (lfo modulation) you hear.

Check if you have used 47pF for C22, and if so check all components connected to pins 5 and 7 of IC4.

I made one mistake...instead of connecting IC4 pin 8 to ground I put it to 9v... corrected that, but I don't know if that could have caused any damage.

Pin 8 IC4 (MN3101) is Vgg output for the BBD and should not be connected to ground, but to pin 4 of IC3 (MN3007).
Since you can hear the BBD clock and a delayed sound,  I think neither IC3 or IC4 are damaged.

Good luck.

André

[Auke Haarsma]

thanks, I may have forgotten C9.... will check that when I get home

[Auke Haarsma]

thnx to Andre! Not only did I forget C9, I also put a wrong cap in C22 indeed! (100 nF...don't ask why, I don't know). Put 47pf in there, and the constant tone is gone! Experimented some, but I have max depth and no added noise with 330pF, so I'll stick to that.

Only problem left is that it distorts. Is that a matter of fine tuning? Heavy stummin on sc or normal strumming on humbuckers results in distortion. Any tips?

[John Lyons]

Ok, I have "NoNothings" CE-2 here and this is what I get.
Slight signal whine variable with speed pot, distorted output, Very sight chorus with no modulation. (may just be the guitars signal modulated by the whining tone)

I get signal at r13 and C10
There is no modulation at pin 7 of IC2.

Voltages: (with 9.6 supply)

IC1
1) 5v   5) 5                  Q1
2) 5   6) 5                    E 4.6
3) 5   7)5                     B 5
4) 0    9.6                 C 9.6

IC2
1) 4.8   5) 4.5              Q2
2) 4.8   6) 4.8v             E 4.9
3) 4.5   7) 4.5               B  5.4
4) 0      9.6               C 9.6


IC3                             Q3
1) 9.6   5) 0                 E 4.7
2) 4.9   6) 4.8              B 5
3) 4.6   7) 4.8              C 9.6
4) .64    4.8

IC4                             Q4               Q5
1)  9.6   5) 0                E  4.7           E  0v
2) 4.8    6) 8.6             B  4.2            B  0v
3) 0       7) 3                C  9.6          C  8.5
4) 4.8    .6


I'm not sure about Q5. There should be some voltage on the base correct?
I have a TL072 in the IC2 position. I've tried another one but with no oscillation still.
I don't have a TL022 here to try
The board is soldered cleanly and there are no solder bridges.

Where should I check?

Thanks

John

[Auke Haarsma]

I have mine still on the breadboard. I have an Tl072 as IC2. You should see some voltages going up and down at pin 7 ic2.
Distortion is probably misbiasing (that's how I cured most of my distortion, but not all, see above). You can quite easily fine tune this with an audio probe at pin 8 of IC3. You should hear quite some modulation there. If you need any speficic measurements from me, let me know.

[John Lyons]

The thing is that I am not getting and modulation fron IC 2. (Pin 7)


John

[Andre]

Here's the voltages of my CE-2:



André

[Auke Haarsma]

edit: -nvm- wrong reading of dmm

[John Lyons]

Thanks Andre for posting your voltages

Those are close to the voltages I get. With the exception of Q5 which I have (C) 8.5v (B) 0v and (E) 0v
I guess I'll try to rebuild the oscillator section and hope that I can find a bad part or value.

I do get a fixed chorus sound but no oscillation. The distortion is still on hard stummed chords though. The trimmer cured a little of it...

John

[Auke Haarsma]

Q5 for me:
C: 9v
b: 0.13 V
e:0.02

hth

[John Lyons]

I measured all the resistors in the Oscillator (TL072) and they measure fine. Replaced the .1uf  cap and still no oscilation.
The voltages are right but it will not oscillate. Anyone think of another place to check? Is there anything other than the TL072 section that would prevent oscillation?

Still get the fixed chorus type sound.

Thanks

John

[Andre]

Although the measured voltages prove me wrong and you say the board is cleanly soldered could you please check this:
If you have a look at the picture of the copper side of the PCB you can see some shiny stuff between one of the depth pot's lugs and one of the pins of R34 which connects to ground. Could this be some drop of solder which does not really short to ground, but maybe act as a capacitor to ground ? It's in the upper left corner of the PCB.

It's probably nothing but I just thought I'd mention it.

André

[Fuzzy-Train]

Is that what you're talking about.

Since John has the board I can't say for sure, but I don't think there's a bridge.

[John Lyons]

Woohoo!
I was cleaning the bottom of the board in order to take some pics and I started resoldering a couple possible cold solder joints.
Cleaned the flux off the board and it fired up. The cold solder joint was it i'm sure.

Here are a couple pics and a sound clip since I already had them ready to go.
Thanks folks for ther help. I'm glad I found the problem because the voltages were right and I wasn't sure where else to check.

CE-2 sound clip

John

[Fuzzy-Train]

OOOOOOOOHHHH YEEEAAAH!!!!!! 

*NoNothing doing the safety dance*

You are a god my good man... I can't believe it was a cold joint, I went over all my joints, desolderd, and then resolderd them and it still wasn't working.

That's awesome man just awesome... any idea which component lead was the culprit?

That clip sounds great... I'm sooo excited to get it back and get that suker in it's case.

Thanks again man.

[Andre]

Now that's good news 

Is that what you're talking about.

Yes, that's the one.

Have fun with your new toy.

André