Echo Base Debugging

[maurice]

Following on from an initial layout problem, I've started this thread specifically for my debugging issue...

Hopefully someone can shed some light

The layout is www.sabrotone.com/wp-content/uploads/2011/05/EchoBase.gif

The effects appear to be working on something (ambient noise / static?) as i can increase feedback, level, time etc but no guitar signal.

I get clean bypass signal if i use the main switch i installed with led but nothing else. The switch i used is http://www.sabrotone.com/wp-content/uploads/2013/01/True_bypass_battery.png

I've started poking around with an audio probe and my clean input signal reaches pins 5,6,7 of IC2.  Also reaches R32 but doesnt pass through. However the signal reaches R21.

I've removed and re-solderdered IC2 just in case and have probed with multimeter.  Still having same problems with audio probe stopping very early on in the circuit.

Substituted Parts:
- R6 used 2x 120k in series
- Q2 used BC109
- Q3 USED 2N5088

Below are the results of meter readings, hopefully they mean more to someone than they do to my novice eyes.  A few 0v readings on Q2, IC3 and D1 if that means anything?:

Battery 8.4
Red 9v+ 5.35
Black lead -1.63

Q1
C 7.68
B 7.63
E 7.63

Q2
C 0
B 0
E 7.03

Q3
C 7.52
B 7.51
E 7.66

Ic1
1 7.73
2 7.29
3 7.69
4 7.54
5 7.8
6 7.08
7 7.72
8 7.36

Ic2
1 7.3
2 7.31
3 7.72
4 7.73
5 7.82
6 7.77
7 7.77
8 7.33

Ic3
1 7.46
2 7.43
3 7.42
4 7.47
5 7.65
6 7.34
7 7.77
8 7.83
9 7.65
10 0
11 0
12 0
13 7.83
14 7.76

Ic4
1 7.82
2 7.83
3 7.83
4 7.83
5 7.32
6 7.77
7 7.45
8 7.45
9 7.51
10 7.47
11 7.56
12 7.55
13 7.55
14 7.54
15 7.5
15 7.5

D1
A 0
K 7.85

D2
A 8.3
K 7.77

D3
A 7.77
K 8.04

[PRR]

> Ic1
> 1 7.73
> 2 7.29
> 3 7.69
> 4 7.54
> 5 7.8
> 6 7.08
> 7 7.72
> 8 7.36
> Ic2
> 1 7.3
> 2 7.31
> 3 7.72
> 4 7.73
> 5 7.82
> 6 7.77
> 7 7.77
> 8 7.33

All your opamp pins are at plus battery voltage. At least one MUST be at negative battery (typically zero volts), several others should then be half battery voltage.

Find your missing ground connection.

[maurice]

Thanks!  I've since cleaned up a bunch of solder joints just to be extra vigilant but still no luck The audio probe now only has signal on IC2 point 8 (I'm guessing the signal doesn't travel through resistors right?).

New meter readings are:
Ic1
1 8.06
2 7.63
3 8.11
4 8.11
5 8.15
6 7.41
7 8.1
8 7.69

Ic2
1 7.68
2 7.68
3 8.1
4 8.1
5 8.14
6 7.67
7 7.68
8 7.7

What could the missing ground connection be?

P.S - Sorry for my electronics naivety and thankyou very much for your help.  It is VERY much appreciated and hopefully once this is working I'll be a lot more aware for the next project.

[PRR]

Is there a schematic? Link?

[maurice]

Here's the one I used:

http://www.sabrotone.com/wp-content/uploads/2011/05/EchoBase.gif

[PRR]

Schematic, not layout.

Something like this, only different:

[maurice]

Unfortunatly I can't find one.  My skills only allow me to follow vero layouts.

[maurice]

Any thoughts on this? I think my own debugging has hit a wall

[mistahead]

Chuck one end of a wire to GND, put a signal through the engaged effect and poke things with the other end of the wire.

It's not getting any less dead staring at it!

(This may not in fact be a good idea, but I do this as a last resort... as a sacrifice ritual in most cases).

[maurice]

Thanks, I've already used an audio probe to similar effect.  No luck though

Really don't want to throw the towel in. Any further suggestions are very welcome.

[slacker]

Like Paul said you appear to have no ground connection. Where have you connected the point marked "ground" on the vero to? When you're measuring the voltages do you have a lead plugged into the input jack? It won't work without one.
You shouldn't be using true bypass with the Echo Base if you want to use the tails feature but we can worry about that once you've got it working.
For a schematic go to  musicpcb.com

[maurice]

Cool, I've spent the last few hours going over every component and joint... Embarrassingly discovered two missing cuts, a misplaced cap point and a backward transistor!  Now everything is DEFINTLY in place though and I've since discovered that soldering a project a big as this in one go just makes mistakes.

I've now got signal that passes through the circuit and gets effected BUT it is very low-fi, quiet and only allows one delay.

I'm almost there, I can feel it in my bones

Just collecting voltage readings again now, but if anyone can suggest anything in the meantime, it's greatly appreciated.

[maurice]

Updated Voltage readings below if anyone can interpret?

Battery      7.98

IC1
1 6.02
2 5.16
3 4.97
4 5.57
5 5.01
6 4.97
7 5.73
8 7.63


IC2
1 4.97
2 4.97
3 4.96
4 0.1
5 4.49
6 4.97
7 4.97
8 7.83

IC3
1 0.55
2 0.55
3 0.55
4 0.55
5 0.6
6 0.54
7 0
8 7.81
9 0.6
10 0
11 0
12 0
13 0.15
14 0.83

IC4
1 4.97
2 2.42
3 0
4 0
5 3.2
6 2.42
7 0.57
8 0.63
9 2.42
10 2.42
11 2.42
12 2.42
13 2.42
14 2.4
15 2.42
16 2.41

Q1
In 7.76
Gnd 0.0
Out 4.96

Q2
E 0
B 0.6
C 1.17

Q3
C 2.41
B 0
E 0

[bluebunny]

IC1
1 6.02
2 5.16
3 4.97
4 5.57
5 5.01
6 4.97
7 5.73
8 7.63

This is still off.  Pin 4 should be 0V (ground).

[PRR]

> ... Embarrassingly discovered two missing cuts, a misplaced cap point and a backward transistor!  Now everything is DEFINTLY in place....

Experience says if there is a bad joint, it is not alone.

As Marc points out, pin 4 sure aint right, which should be "simple"; and I suspect that's not the last problem.

I'll gleefully admit that I once found and fixed a dozen problems, the dingus still didn't work, and it took me MONTHS to find the last critical mistake (and then some more minor errors). Experience makes you better, they say; I've become sometimes good at finding my mistakes, but last month I tried to sort some wiring and ended up sealing it into the wall un-fixed.

[mistahead]

but last month I tried to sort some wiring and ended up sealing it into the wall un-fixed.

Is that like the time I "Dropped" my TI scientific calculator due to frustration, and once I'd fished it out of the space between the gyprock sheets that divide the rooms in that house... except without the part where you get it back out?

[maurice]

Ha, I'm hoping I don't get to the burying stage just yet.

I've just been goin over any joint that look as though they could be bad.  Also, taken out the true bypass switch (now have no switch at all) but still have quiet, lo-fi sound but some of the voltage have changed?  Do these new results suggest problems to anyone?

Battery      7.92

IC1
1 6.49
2 5.44
3 4.97
4 5.56
5 5
6 4.97
7 5.84
8 0.02


IC2
1 4.97
2 4.97
3 4.94
4 0
5 4.48
6 4.97
7 4.93
8 7.89

IC3
1 0.64
2 0.66
3 0.66
4 0.67
5 0.71
6 0.65
7 0
8 0.92
9 0.27
10 0
11 0
12 0
13 0.82
14 7.88

IC4
1 4.96
2 2.42
3 0
4 0
5 3.17
6 2.42
7 0.72
8 0.72
9 2.42
10 2.40
11 2.41
12 2.42
13 2.42
14 2.42
15 2.42
16 2.42

Q1
In 7.86
Gnd 0
Out 4.97

Q2
E 0
B 0.6
C 1.17

Q3
C 2.42
B 0
E 0

[mistahead]

Just reading what others have said, and looking at your recent repost - you still have something wrong at IC1 pin4... solder bridge?

(Note - I'm just reinterpreting smart people).

[maurice]

hmmmm, weird. I've the connection from gnd to IC1 pin 4 seems good (checked continuity and ohms).  What could be making it such a high voltage?

[maurice]

also, the led isn't working if that suggests an obvious problem.  Does it need a resistor?