Sunking - Repeating Pop that goes faster as gain is increased

[bigp7099]

Hi i'm building a version 3 sunking and I get a repeating popping or thud sound when i have the gain turned up about 1/3-1/2 way. It goes faster the higher i turn up the gain. I have checked values and orientations and solder, especially around the ic's. I haven't gotten all the way through it with the audio probe yet.

i searched and can't find a thread where somebody else gets the same problem but it seems like it would be very specific.

Any help would be much appreciated.

[jkokura]

That does seem odd.

Couple things will help us:

1. Give us a list of the IC's you're using specifically (including the letters)

2. Give us your voltages on each pin of the ICs

3. Give us a clear idea of any mods or substitutions you may have done, and any steps you've taken in debugging so far

We'll get it going for you as best we can from the other side of our computer screens.

Jacob

[mgwhit]

Clicks, pops and thuds can frequently be traced back to capacitors charging and releasing.  The orientation really shouldn't matter for C9 and C11, but since you're having problems I'd triple check them anyway.  I'd also triple check the orientation of C10.  I hope it's not a bad cap, but if it is, the audio probe is the way to find it.

In addition to what Jacob has requested, I always find good, in-focus close-up photos helpful.

Good luck!

[bigp7099]

ok so here are the IC's and pin voltages, can already see i have some problems according to the voltages in the project doc, the battery was 9.11v when i started checking and 8.88v when i was done

IC1 - TL072CP
1 4.05
2 4.04
3 0.96
4 0
5 3.88
6 4.01
7 4.02
8 7.99

IC2 - TL072CN
1 13.06
2 3.84
3 3.94
4 -7.59
5 3.93
6 3.98
7 -5.08
8 14.07

IC3 - 7660SCPAZ
1 7.93
2 3.90
3 0
4 -3.74
5 -7.52
6 3.28
7 2.85
8 7.90

I'll check parts around the pins that are way off if anybody else has any thoughts specifically what i should be looking for please let me know

[bigp7099]

ok so i found a problem with the parts connecting to pin 1 on IC2 and now it is working and kind of sounds right.

checked all the voltages again and pin 3 on IC2 (.98) and pin 7 on IC3 (2.68) still aren't close so i guess i'll check around those next

[bigp7099]

ok so i have investigated some more and i think i might have found a problem

at IC3 pin 1 i have 7.54V
after R25 i have 3.73V
after R26 i have 0V?
after R2 (IC1 pin 3) i have .94V

is this the problem? should R25 be cutting the voltage in 1/2? i used a 1/2 watt for R25 and R26 resistor instead of 1/4 or 1/8 as it was all i could find but that shouldn't matter

[mgwhit]

Sounds like your battery is weak, which I think you mentioned earlier.  I think something is drawing too much power.  You should have 9+V on IC3:pin1.  Your voltage divider at R25 and R26 is working correctly, in that it is approximately halving the voltage it's being provided (7.54/2 = 3.77 =~ 3.73).  The 1/2 watt resistor shouldn't matter at all (except in size). When you say you see 0V "after R26", I assume you mean between R26 and ground.  Anytime you connect directly to ground, you should see 0V.  The 0.94V at IC3:pin3 concerns me for that very reason.  Wondering if the weak battery could cause that.

[bigp7099]

got some fresh batteries and pin 1 on ic3 is 9.5v

pin 3 on IC1 is still only 1.11v

[bigp7099]

ok so i decided to just play through it again and it sounds way better, a lot more like i expected it too

should i worry about the voltage at pin 3 or not? maybe i'm still not getting everything out of it?

[mgwhit]

If there's still voltage at IC3:pin3, I'd be concerned about it.  Have you tried it with a 9V adapter?

[bigp7099]

i have it's boxed up and sounding good right now ao i'm going to leave it for the time being and work on some other stuff

1 small issue, there is a bit of a hum that goes away when i touch the footswitch, any idea how to fix it, not a big deal but if anybody knows what the fix is it would be appreciated

[ckim715]

sounds like a grounding issue. Double check your grounds, make sure they are good.