Help with Tonepad Small Clone Chorus (Heladito-02)

[96ecss]

I built a Small Clone chorus from the layout at Tonepad. http://tonepad.com/getFile.asp?id=97 All IC's and transistors are socketed. No parts substitutions.

There is no sound when turned on. I took voltage readings and probed with an Audio Probe. The frustrating thing is that I can't follow the schematic as easily as I can follow the schematic for a boost or OD pedal so I'm not sure what I'm supposed to be getting where. If that makes any sense.

First here are my voltage readings.

Battery Voltage - 9.52

Battery In at PCB - 9.50

Ground at PCB - 0

D1:
Cathode - 5.52
Anode - 6.06

D2:
Cathode - 7.05
Anode - .08

Q1: 2N5087 PNP
C - 0
B - 4.88
E - 5.50

Q2: 2N5088 NPN
C - 9.24
B - 5.40
E - 4.84

Q3: 2N5088 NPN
C - 9.18
B - 9.15
E - 8.57

IC1 - 4558
1 - 6.44
2 - 6.45
3 - 6.23
4 - 0
5 - 6.37
6 - 6.38
7 - 8.51
8 - 9.17

IC2 - LM358
1 - varies
2 - 4.20
3 - 4.17
4 - 0
5 - varies
6 - 2.27
7 - varies
8 - 9.15

MN3007
1 - 8.49
2 - 4.21
3 - 5.96
4 - 0
5 - 0
6 - 4.19
7 - 5.49
8 - 5.49

CD4047
1 - 8.31
2 - .09
3 - 7.05
4 - 8.48
5 - 8.48
6 - 8.48
7 - 0
8 - 0
9 - 0
10 - 4.19
11 - 4.20
12 - 0
13 - 8.31
14 - 8.47

With an Audio Probe I have sound at Pin 3 of the MN3007 and Chorus at Pins 7 and 8 of the MN3007. The Speed and Depth knobs both work at that point. There is no sound at all anywhere on the CD4047.

I checked for solder bridges with a lighted magnifying glass and there doesn't seem to be any. I touched up a couple of solder points but it didn't make a difference.

Any help would be greatly appreciated.

Thanks,

Dave

[Pushtone]

Sounds like your signal is getting shorted to ground somewhere.

Is it mounted in a box? If so try taking the whole thing, jacks, switch and all, out and testing.

The LM358 is varing the volatages ok but does the sweep speed up and slow down when adjusting the speed knob?
If so your CD4047 is working correctly. That only leaves a short to ground.

Might be time for a detailed gut pic.


opps hold on.... just noticed the voltages for Q3 look off. I'd focus on that area.

[96ecss]

Thanks for the help Pushtone. It is on my test board, not in a box yet. The Speed and Depth knobs both work correctly. What do you notice about Q3? Are the Base and Emmiter too high?

Dave

[Pushtone]

Thanks for the help Pushtone. It is on my test board, not in a box yet. The Speed and Depth knobs both work correctly. What do you notice about Q3? Are the Base and Emmiter too high?

Dave

Hold on, I'll put on some pants and check the voltages on mine.

[markm]

Thanks for the help Pushtone. It is on my test board, not in a box yet. The Speed and Depth knobs both work correctly. What do you notice about Q3? Are the Base and Emmiter too high?

Dave

Hold on, I'll put on some pants and check the voltages on mine.

[theehman]

You shouldn't have any guitar signal anywhere on the 4047, so that's fine.  Check the base and emitter of the Q2 for chorused signal.  If that looks good, you may have Q3 installed wrong.

[96ecss]

Thanks for the help.

There is chorused signal on the Base and Emmiter of Q2. I tried 2 different trannies in Q3 and switched the orientation of both with no difference in output. 

Dave

[Pushtone]

Haven't checked mine yet (still pantless in Vancouver) but I did search for "Small Clone voltages" and there are several posts with voltages and Q3 is close to 8v on all pins so I'm guesing that is not your problem.

I'd suggest doing the same search and comparing the voltages others have posted to yours.

I remember when I built mine I didn't notice the polarity marking on the one tantulum cap and had put it in wrong.

I still think your signal is getting shorted to ground.
Others report signal but no chorusing which would be an LFO issue. No signal suggests a short.

[theehman]

Thanks for the help.

There is chorused signal on the Base and Emmiter of Q2. I tried 2 different trannies in Q3 and switched the orientation of both with no difference in output. 

Dave

Next step is to just see if the chorused signal is actually making it to Q3.  Also, does the LED light up when the effect is turned on?

[slacker]

I think the problem is with pin 7 of IC1 it should be about the same as the other pins, if there's something wrong there you'll get no sound. Check round there for shorts and double check the component values as well.

Next step is to just see if the chorused signal is actually making it to Q3.  Also, does the LED light up when the effect is turned on?

Think you must be looking at a different schematic on the tonepad schematic Q3 is nowhere near the audio path.

[theehman]

Next step is to just see if the chorused signal is actually making it to Q3.  Also, does the LED light up when the effect is turned on?

Think you must be looking at a different schematic on the tonepad schematic Q3 is nowhere near the audio path.

You're right.  I was looking at a different schematic.  Definitely check the inputs and output of IC1B.  It's getting lost somewhere between there and Q2.

[96ecss]

PROBLEM SOLVED!

I found a solder bridge near pin 7 IC1. 

Many many thanks for all your help!!!

Now I can work on some mods.

Dave

[sovtek50]

Man, I had a hard time debugging a "handwired" PCB of this circuit. Some time later, I sold the finally working pedal to a friend and decided to build another one. This time I ordered a PCB from Tonepad. Surprise, surprise, not only was it much easier to get it done, but it also sounded much better! Don't know why, maybe a coincidence or I still had a mistake on the first one. All I know, I'll never build circuit which are a tad more complex from pad-per-hole boards again. Support Tonepad, GGG, etc.