[SOLVED] FuzzDog Super Skwisher debugging - no signal at all

[VidSicious]

Hey! So it's been awhile and I recently got back into building which is awesome but for god's sake this circuit is just driving me nuts.

I believe I checked everything I can: the orientation of polar caps, diodes (the upright diode's striped leg is going to square pad as per instructions), the transistors and IC. I tried to resolder some bits but it just won't give me any signal apart from humming.
The battery I use is definitely alive, I tried several in fact. The level knob does work, the sustain and the switch do nothing.

Please please help

Build Documents (I'm going for Mark Hammer mods)

Photos

[ElectricDruid]

The board looks fine and I checked the resistor and cap values against the photo in the build doc and couldn't see anything wrong.

Can you post the voltages at the IC pins and transistors? We might be able to spot something weird there.

After that, I'd audio-probe it. The output of the first buffer transistor would be the place to start. Is there any signal there?

HTH,
Tom

[VidSicious]

Thanks for looking over this ElectricDruid!

I've probed and the signal is there at Q1 but it's gone by Q2

IC (LM13700) voltages:

1. 8.74        9. 8.31
2. 8.30        10. 8.31
3. 8.03        11. 8.31
4. 7.80        12. 7.77
5. 8.45        13. 8.34
6. 8.77        14. 9.43
7. 1.32        15. 1.35
8. 8.44        16. 8.48


Transistor voltages
Q1 E: 8.67 B: 5.14 C: 9.32
Q2 E: 8.67 B: 8.44 C: 9.32
Q3 E: 8.78 B: 8.40 C: 9.32
Q4 E: 8.76 B: 8.42 C: 9.32
Q5 E: 8.93 B: 9.32 C: 9.42

[PRR]

> IC (LM13700) voltages:
1. 8.74        9. 8.31
2. 8.30        10. 8.31
3. 8.03        11. 8.31
4. 7.80        12. 7.77
5. 8.45        13. 8.34
6. 8.77        14. 9.43
7. 1.32        15. 1.35
8. 8.44        16. 8.48

On most single-supply chips, you expect one pin to be at battery voltage, another pin to be at zero.

Also all your transistor voltages look like small drops from battery, no zero volt return.

You don't have your battery negative connected.

(I didn't look at the plan. On many pedals you need a plug in a jack to make the ground and get power.)

Here everything is essentially battery voltage!!

[bluebunny]

(And you may have numbered your pins wrong: 1-8 down the left, 9-16 UP the right.  But we won't know for sure until you sort out your power and ground as Paul says.)

[VidSicious]

Hey again! Thanks for all the input. Yes it seems I did have ground issues. I wasn't aware the guitar has to be plugged in! How strange. Anyway, I took a second reading with my cheap multimeter (some 0.01 values might actually be 0 instead). Here it is:

PSU: 9.09
IC (LM13700):
1. 1.33         16. 0.03
2. 0.04         15. 0.02
3. 3.69         14. 0.01
4. 3.69         13. 0.01
5. 2.13         12. 0.11
6. 0.01         11. 9.09
7. 0.01         10. 0.01
8. 0.12           9. 0.09

2N5089:
Q1 E: 1.98 B: 1.41 C: 7.05
Q2 E: 1.90 B: 2.13 C: 7.11
Q3 E: 0.00 B: 0.01 C: 7.77
Q4 E: 0.00 B: 0.02 C: 7.77
Q5 E: 9.09 B: 7.75 C: 8.41

[bluebunny]

How strange.

It's how you can leave a battery in the pedal without it draining when not in use: you simply remove the input lead.  It works its magic by completing the connection to ground (which is where one end of the battery lives).  No connection, no battery, no power drain.  But no ground connection for the rest of the circuit, either!  Hence the weird readings previously.

[VidSicious]

Oh yes, of course, the good old input ground battery trick! I haven't boxed this circuit due to the issues and aren't implementing this feature as of yet.

Edit: this makes me wonder how in the world I got those voltages the first time round

[VidSicious]

UPDATE: It is fixed! I knew it would be something very silly on my part. The photo in the build docs didn't match the actual layout and I put a jumper between 2 wrong pot pads. It works as a charm now! Thanks everyone for chipping in, love the community and you're all very beautiful people!