Tonepad Small Clone Debug + CD4047 test (post 2 by slacker)

[strungout]

EDIT: Change the thread title.

Hey,

So while I'm waiting for a pcb for the Echo Base, I'm breadboarding choruses. Little Angel, Zombie (can't get it to stop ticking but then again I had a heap of wires and components acting like antennas, maybe I'll try it on vero with SabroTone layout) and now, a Small Clone (EDIT: forgot to link the schem: http://www.tonepad.com/getFile.asp?id=97 ).

The dry signal passes through to the output. So does the wet signal (goes in and out of the MN3007) but it isn't modulated. The LFO works as per the blinking LED mod I added and I mesured it too anyway. It makes it to the CD4047 though the variation in voltage is 10-30mV at pins 10 and 11 and even less at pins 2 and 6 of the MN3007.

How would I got about checking if the CD4047 is bad? Note that I only have one of them atm. Gonna buy some next week.

[slacker]

To test the CD4047 you could build the circuit shown here http://www.learningaboutelectronics.com/Articles/4047-astable-multivibrator-circuit.php it will work fine on 9 volts instead of 5. None of the component values are critical just use whatever you have of a similar value.

[strungout]

Hey slacker, nifty little circuit! Thanks! It worked great and my CD4047 is not busted. Though I kinda wished it was. Easy fix... Now I gotta figure out what the real problem is

Maybe you can help with another thing before I officially call this a Small Clone debug thread(!): I get 9.33V from my power supply and it's what I see at the battery side of the 47R going to the 220uF cap, etc. and after that 47R, my voltage swings from 8.80V - 9.07V (and Vref is moving too from 4.50V - 4.52V, of course)... That's not normal, is it? First time I encounter this issue.

I got to go right now, but I'll post my info and other voltages when I'm back.

[anotherjim]

To the MN3007, pins 2 and 6 will have square wave drives from the CD4047 with 50% duty cycle. That is they spend just as much time switched to the high logic level as the low level. When you measure that with a DMM set for voltage you will get the average of that square wave which is usually half of the power supply voltage. When the LFO is modulating the clock frequency, the 50% duty cycle never really alters (it is stretching and squeezing the square wave but the DMM reads an average) so the DMM voltage measure of the clock will not change much at all.
Since the clock pins are wired to the 4047 pins 11 & 10, the voltages ought to read the same there.

The place to see modulation to the 4047 is its pin3 with the LFO depth pot at maximum.

[strungout]

To the MN3007, pins 2 and 6 will have square wave drives from the CD4047 with 50% duty cycle. That is they spend just as much time switched to the high logic level as the low level. When you measure that with a DMM set for voltage you will get the average of that square wave which is usually half of the power supply voltage. When the LFO is modulating the clock frequency, the 50% duty cycle never really alters (it is stretching and squeezing the square wave but the DMM reads an average) so the DMM voltage measure of the clock will not change much at all.
Since the clock pins are wired to the 4047 pins 11 & 10, the voltages ought to read the same there.

The place to see modulation to the 4047 is its pin3 with the LFO depth pot at maximum.

I see. So what I observed at those pins is normal operation. Cool.


So, then, some info and voltages.

-Small Clone from Tonepad on breadboard: http://www.tonepad.com/getFile.asp?id=97 with Depth pot mod.
-Only derrogation to the schematic is I used a 100pF and 82pF in parallel instead of the 180pF (at the base of Q2)
-Dry signal passes.
-Wet signal passes through the MN3007 but is not being modulated despite a varying voltage on pin 2 and 6, and pin 10 and 11 on the CD4047.
-The LFO works, I added an LED and it flashes slow or fast along with the Rate pot rotation.
-Vcc after the 47R resistor is not stable, it shifts from 8.80V - 9.07V.
-There is no chorus and, using a multi-turn trimmer (voltage changes more slowly, so I'm thinking I can fine tune it more easily), I'm going real slow and I cannot find a sweet spot. Right now it's set at about 5.25V (Because of what I mentioned about the Vcc, it goes up and down slightly).
-I tried searching for a similar problem on the forums but nothing turned up for me. The resistors are the right value. So are the caps and they are oriented correctly. The diodes and transistors too (both types have the same pinout; EBC). No component leads are touching any other. Everything that should be grounded is. Everything that should be connected to Vcc is. Same with Vref. I checked and rechecked my connections about4 times, last two I didn't find anything at the wrong place. I tried the 5 different MN3007s I have. No Change.

On to the voltages:

Supply: 9.33
After the 47R: 8.96-9.05
Ground: 0.00-0.01

IC1 - RC4558
1-4.55
2-4.53-4.57
3-4.42-4.45
4-0
5-4.48-4.59
6-4.49-4.54
7-4.47-4.50
8-8.86-9.05

MN3007 (bought a long time ago, like 10 years at least, kept in a static free case, manufacturer symbol looks like a Tri-force... 'member The legend of Zelda?
1-8.25-8.36
2-4.15-4.22
3-3.01-3.04
4-0
5-0
6-4.14-4.22
7-3.01-3.05
8-3.02-3.05

CD4047
1-8.03-8.18
2-0.15
3-7.36-7.49
4-8.25-8.40
5-8.25-8.40
6-8.25-8.40
7-0
8-0.00-0.01
9-0.00-0.01
10-4.15-4.22
11-4.15-4.22
12-0.00-0.01
13-8.05-8.21
14-8.25-8.40

IC2 - LM358
1-1.21-2.28
2-3.96-4.04
3-3.92-4.01
4-0
5-1.45-2.94
6-2.16-2.20
7-0.56-7.42
8-8.85-9.05

Let me know if you need more info.

EDIT: I obviously I busted my DMM... Decided to check the value of that 47R resistor, set the range to 200R and the readings are all over the place, but above 47R. Tried another. Same deal. Tried another on the 2000R range this time. Bah! Tried a 4.7k res at the 20k and 200k range, it reads as a 47k... (the bands on this particular one are big and easy to read). I shorted it to +9V while connecting the negative lead to the power supply negative lead with an alligator clip. I had a spark... Forgot to unplug the adaptor... Great, I need to buy a new DMM... I'll ask around in the meantime so I can keep debugging this.

[ElectricDruid]

EDIT: I obviously I busted my DMM...

You might just have blown a fuse or something. Some or them have little fuses in or other "sacrificial" components to protect the inputs. I burned my way through quite a few on my last meter, but it still kept going for thirty years. Worth taking the back off and having a look before you go shopping, anyway.

[Fender3D]

Hi Frank,
my deepest condolences for your DMM (check if it has a burned fuse inside btw).
I know 0.27V could be a huge supply variation sometimes, but not in this circuit...
Don't harass the poor 47 ohm resistor... your LFO is not modulating than isssue can't be there (on the 47 res I mean).

IC pin 1 swings barely 1V, it should swing ~4V if memory serves me well...
Check around IC2 what's going wrong.

Edit:
Tom beat me about the fuse

[duck_arse]

a question about your method - you aren't trying to measure the resistor resistance while the circuit is powered, are you?

[strungout]

ElectricDruid: Oh, I assumed if the fuse was blown, it would just be dead. I figured I must've burned some res's/caps. I checked the fuse but I can't see inside it on the count of it being opaque white... I'm gonna check if I have another and see if it works right again. I already went and ordered a new DMM. After the initial disappointment,I realized I actually could use a better DMM. I bought one that goes read up to 40MOhm (vs 2M on the old one), has a continuity function, hFE tester and is likely more precise (the old one is 10 years-old and was maybe 20$. I spent a bit more on the new one). It even tests temperature... That's crucial in pedal building, right? I should have it tomorrow.


Fender3D: Hahaha! I've checked and rechecked, but I'm certainly gonna check again. All my chips have been replaced. Just in case. I'm gonna test them in the circuit once I get it working. And I'm gonna repost voltages when I have a working DMM.


duck_arse: Nope, no worries. It's one of the first things I learned. It's on my breadboard, so I just took it out.


I'll keep you guys posted.

[anotherjim]

If the meter has a milliamp range available with the same probe sockets as the voltage/resistance ranges, then there could well be a fuse. More often a fuse is provided for the full ampere ranges that are only available from a separate probe socket and shouldn't affect the other ranges when (not if) you blow it.

[strungout]

Welp, I found the culprit: dead breadboard hole... Sigh. After checking my connections so many times, sitting and trying to stare it down into working, it dawned on me that maybe I had a dead spot like in my old breadboard (had actually learned to work around them... sad), I moved the LFO to another piece of board, unplugged the dry signal 22k res and fiddled with the trimpot and whaddya know the effect came in. Was so psyched! And I even resisted playing Come As You Are... Hahaha. I mock-played the intro to Radio Friendly Unit Shifter instead (off of In Utero)

I'm not quite done yet, tho. I need to find my sweet spot. I suggest that builders who make this circuit use a multi-turn trim pot, it makes it way easier to fine-dial it in and you won't risk missing it. The range is quite big when you're turning only 10's of mV at a time.

The transistion is not very smooth, tho. To my liking anyway. What can I do to smooth out the LFO wave? It's a triangle one, right?

(...) when (not if) you blow it.

That made me feel a bit better! The 'when' part

[strungout]

Just forgot to say thanks to you guys for helping out!

[strungout]

There's still one thing that bugs me: why is the voltage after the 47R not stable (it is before it, and straight from my +9vdc 1spot adapter? What's causing it? Is that normal for this pedal? I want to put up working voltages for my build for reference for other Heladito-02/Small Clone clone builders, but I have to know if this voltage instability is normal...

[Fender3D]

CMOS oscillators use the more current the higher they oscillate...
Voltage will change with LFO rate, then.

BTW
you may toss the resistor and connect power supply without it

[strungout]

CMOS oscillators use the more current the higher they oscillate...
Voltage will change with LFO rate, then.

BTW
you may toss the resistor and connect power supply without it

Makes sense. Thanks for clearing that up!


EDIT: Hahahaha! Now that I removed the 47R, the voltage barely moves...


Voltages of my working unit:

Power: 9.39
Vref: 4.70
Ground: 0.00

IC1 (Buffers; RC4558)
1-4.75
2-4.74
3-4.61
4-0.00
5-4.70
6-4.72
7-4.72
8-9.38

MN3007
1-7.83
2-3.92
3-5.30
4-0.00
5-0.00
6-3.91
7-4.83
8-4.83

CD4047
1-7.66
2-0.12
3-3.72
4-7.06
5-7.06
6-8.12
7-0.00
8-0.00
9-0.00
10-3.51
11-3.64
12-0.00
13-3.74
14-7.06

IC2 (LFO; LM358)
1-0.92 - 2.72
2-4.17
3-4.13
4-0.00
5-1.06 - 3.76
6-2.26
7-0.03 - 8.13
8-9.37

[strungout]

Can't edit my posts... Needed to change the info and add some that's missing.


Working Unit Voltages:

Power: 9.37
Vref: 4.5
Ground: 0


Q1 (2N5087)
E: 3.94
B: 3.32
C: 0

Q2 (2N5088)
E: 3.15
B: 3.7
C: 9.04

Q3 (2N5088)
E: 8.35
B: 8.98
C: 9.05


IC1 (RC4558)
1: 4.56
2: 4.57
3: 4.41
4: 0
5: 4.5
6: 4.52
7: 4.46
8: 9.04

MN3007
1: 8.35
2: 4.21
3: 4.47
4: 0
5: 0
6: 4.21
7: 3.8
8: 3.8

CD4047
1: 7.95
2: 0.24
3: 7.20 - 7.29
4: 8.35
5: 8.35
6: 8.35
7: 0
8: 0
9: 0
10: 4.21
11: 4.21
12: 0
13: 7.96 - 8.00
14: 8.35

IC2 (LM358)
1: 0.96 - 2.93
2: 4.01
3: 3.97
4: 0
5: 1.55 - 3.31
6: 2.18
7: 0.03 - 7.82
8: 9.04

D1 (1N914)
A: 4.49
K: 3.94

D2 (1N914)
A: 0.25
K: 7.02 - 7.30

[AdrianM55]

MN3007
1: 8.35
2: 4.21 /fluctuating to 8v
3: 4.47
4: 0
5: 0
6: 4.21.  / 0-8.03 fluctuating
7: 3.8.  / 5.21
8: 3.8.   / 5.21

CD4047
1: 7.95
2: 0.24 / 0
3: 7.20 - 7.29 / 4v
4: 8.35 /8.03
5: 8.35
6: 8.35
7: 0
8: 0
9: 0
10: 4.21
11: 4.21 /fluctuating 0.012 to 0.024
12: 0
13: 7.96 - 8.00/ 8.03
14: 8.35.  /8.03

My one is the clone theory reissue any ideas?

[Kevin Mitchell]

My one is the clone theory reissue any ideas?

You'd be better off starting a new thread specifically for your debugging efforts. Preferably with further details about the condition/problem with the pedal.

That being said, nothing seems obviously wrong with the provided voltages.

[Fender3D]

My one is the clone theory reissue any ideas?

And the issue is?

BTW

3007 pin 4 should be somewhat higher than 0V

4047's pins 10 and 11 should be similar (both fluctuating in your case).
check with o-scope or freq. meter if you have clock there...

[Kevin Mitchell]

3007 pin 4 should be somewhat higher than 0V

Not when it's tied to ground.
You're expecting to see 0.6v (1/15th of VDD). But that isn't what the pin is being supplied in this design.