Author Topic: Sunking Low Output Trouble  (Read 1310 times)

topherdo

  • Diode Destroyer
  • *
  • Posts: 6
    • View Profile
Sunking Low Output Trouble
« on: July 12, 2011, 08:09:33 PM »
I just finished building a sunking and it worked fine at first, but then when I came back to test it again I was  getting a really low fizzy output sound with and without the pedal being active. After much fiddling and frustration I found that if I short my board at a certain point (by quickly tapping the two points with a short piece of wire) it would go back to normal and stay that way for a bit. I can't figure out what could be causing this to occur and would much appreciate any insight at all.

Below I have circled the two points I mentioned in my post.


madbean

  • Administrator
  • Electron Doctor
  • *****
  • Posts: 9498
  • Brian
    • View Profile
    • madbeanpedals
Re: Sunking Low Output Trouble
« Reply #1 on: July 12, 2011, 10:10:33 PM »
Something is amiss with your voltage supply on the board, I think. When you short those two traces, you are supplying about 9v instead of 4.5v bias to IC2. We'll need more voltages off your ICs to diagnose the problem (without shorting the two traces, I mean).

Also, if you made any substitutions on parts let us know. What charge pump are you using?
No matter where you go, there I am. Watching you.

topherdo

  • Diode Destroyer
  • *
  • Posts: 6
    • View Profile
Re: Sunking Low Output Trouble
« Reply #2 on: July 13, 2011, 12:14:39 AM »
Man, my multimeter just had to die the night I really need it. ha ha. I did not make any substitutions, I built it exactly like the project file describes it using the single sided board. I'll try to get some voltages as soon as my multimeter is working. Is there anything else I can try in the meantime?

topherdo

  • Diode Destroyer
  • *
  • Posts: 6
    • View Profile
Re: Sunking Low Output Trouble
« Reply #3 on: July 16, 2011, 02:41:57 AM »
Alright I got the voltages:

IC 1 (TL072BCP)
1 - 4.57
2 - 4.57
3 - 3.51
4 - 0
5 - 4.56
6 - 4.57
7 - 4.58
8 - 9.16

IC 2 (TL072BCP)
1 - 4.58
2 - 4.57
3 - 4.57
4 - (-8.83)
5 - 4.57
6 - 4.57
7 - 4.57
8 - 16.75

IC 3 (7660SCPA)
1 - 9.16
2 - 4.59
3 - 0
4 - (-4.38)
5 - (-8.58)
6 - 4.58
7 - 7.00
8 - 9.16

Thanks in advance for the help!
« Last Edit: July 16, 2011, 10:34:35 AM by topherdo »

gtr2

  • Electron Doctor
  • *****
  • Posts: 4784
  • Josh
    • View Profile
    • 1776 effects
Re: Sunking Low Output Trouble
« Reply #4 on: July 16, 2011, 07:45:23 AM »
Are the voltages on IC3 for pins 4 and 5 negative?  They should be, I imagine it's a typo, everything else looks good voltage wise.

Josh
1776 EFFECTS STORE     
Contract PCB designer

topherdo

  • Diode Destroyer
  • *
  • Posts: 6
    • View Profile
Re: Sunking Low Output Trouble
« Reply #5 on: July 16, 2011, 10:35:17 AM »
You're right. Whoops. I've gone ahead and corrected the voltages. I have no idea what is wrong then. hmmm

gtr2

  • Electron Doctor
  • *****
  • Posts: 4784
  • Josh
    • View Profile
    • 1776 effects
Re: Sunking Low Output Trouble
« Reply #6 on: July 16, 2011, 12:02:22 PM »
Some pictures of everything may help...

Also an audio probe may be useful.  They are easy to build in a few minutes.  Start at the beginning of the circuit and find where your loosing signal.

http://diy-fever.com/misc/audio-probe/
1776 EFFECTS STORE     
Contract PCB designer

topherdo

  • Diode Destroyer
  • *
  • Posts: 6
    • View Profile
Re: Sunking Low Output Trouble
« Reply #7 on: July 16, 2011, 12:09:19 PM »
Ok I'll try that. It's a very weird thing. As of right now it is working but every once in a while I'll turn it on and the output will be really low and super fizzy. I short the circuit where I marked in the original post and it'll jump to life like I had just turned it on. It is very odd. I'm waiting until it does it again to get another voltage reading to see if it is different.