Author Topic: Merman Fizz—Solved!  (Read 458 times)

Droogie

  • Electron Doctor
  • *****
  • Posts: 635
  • Andrew
    • View Profile
Merman Fizz—Solved!
« on: September 03, 2017, 01:31:55 PM »
Fired up the Merman and it works, but am getting unwanted, verging on farty, breakup from the Bottom control and fizz from the Warm control (which I can almost dial out by backing off Warm and treble). I checked components and reflowed and my voltages are close (maybe pin 6 of the 7662 is low?)
9.18 V from power supply
IC 1
1 4.29
2 4.3
3 3.05
4 1.5mV
5 4.26
6 4.26
7 4.3
8 8.57

IC2
1 4.25
2 4.29
3 4.29
4 -8.49
5 4.29
6 4.29
7 4.34
8 16.62

7662
1 8.57
2 5.04
3 1.5 mV
4 -3.9
5 -8.49
6 3.59
7 5.06
8 8.56

Any thoughts on what might be the issue?

Thanks!

« Last Edit: September 07, 2017, 06:36:27 AM by Droogie »
Chief Executive Officer in Charge of Burrito Redistribution at Hytone Electric

madbean

  • Administrator
  • Electron Doctor
  • *****
  • Posts: 7704
  • Brian
    • View Profile
Re: Merman Fizz
« Reply #1 on: September 03, 2017, 01:59:36 PM »
Are you getting the fizz when the comp pot is all the way up? The clipping diodes could be a cause. Your voltages look fine.
I own madbeanpedals (duh). I am part owner of Function F(X).

Droogie

  • Electron Doctor
  • *****
  • Posts: 635
  • Andrew
    • View Profile
Re: Merman Fizz
« Reply #2 on: September 03, 2017, 02:06:06 PM »
Yes. I was using D9Es and tried removing them altogether, same issue. Random thought: used a tant for 4u7. Any noise issues in that spot with a tant?
Chief Executive Officer in Charge of Burrito Redistribution at Hytone Electric

Droogie

  • Electron Doctor
  • *****
  • Posts: 635
  • Andrew
    • View Profile
Re: Merman Fizz—Update
« Reply #3 on: September 04, 2017, 10:59:40 AM »
Swapped out the Tant 4u7 and got rid of the verging on farty breakup from the Bottom pot. Still have fizz though. Will check values again and keep digging. Getting closer!
Chief Executive Officer in Charge of Burrito Redistribution at Hytone Electric

gordo

  • Electron Doctor
  • *****
  • Posts: 1166
    • View Profile
    • Project Website
Re: Merman Fizz—Update
« Reply #4 on: September 04, 2017, 09:27:17 PM »
Check values. Mine made its debut yesterday (I'll post pics) and it's a keeper. Warm to edgey but definitely not fizzy. Stock build.

Droogie

  • Electron Doctor
  • *****
  • Posts: 635
  • Andrew
    • View Profile
Re: Merman Fizz—Update
« Reply #5 on: September 05, 2017, 10:52:10 AM »
I'm definitely going to swap out a few ceramic caps for film, and try the low esr 22u caps as well. The values are good so I'm thinking to make the build closer to the exact specs called for.
Chief Executive Officer in Charge of Burrito Redistribution at Hytone Electric

Ralfg

  • Stompbox Star
  • ***
  • Posts: 176
  • Ralf
    • View Profile
Re: Merman Fizz—Update
« Reply #6 on: September 05, 2017, 11:10:47 AM »
Have you tried some different ICs? Just thinking it could be your opamps could be bad.

Droogie

  • Electron Doctor
  • *****
  • Posts: 635
  • Andrew
    • View Profile
Re: Merman Fizz—Update
« Reply #7 on: September 05, 2017, 11:47:22 AM »
Have you tried some different ICs? Just thinking it could be your opamps could be bad.
It's possible. I may end up replacing every part in this thing until it works!  :)
Chief Executive Officer in Charge of Burrito Redistribution at Hytone Electric

Droogie

  • Electron Doctor
  • *****
  • Posts: 635
  • Andrew
    • View Profile
Re: Merman Fizz—Solved!
« Reply #8 on: September 07, 2017, 06:38:10 AM »
Per Ralfg' suggestion, I replaced IC2 and no more fizz! I think in about 100 pedals built, it was the first bad IC I have encountered. Now to explore the sounds!
Chief Executive Officer in Charge of Burrito Redistribution at Hytone Electric

Ralfg

  • Stompbox Star
  • ***
  • Posts: 176
  • Ralf
    • View Profile
Re: Merman Fizz—Solved!
« Reply #9 on: September 07, 2017, 07:05:52 PM »
Yeah!  Glad you got the problem resolved.

madbean

  • Administrator
  • Electron Doctor
  • *****
  • Posts: 7704
  • Brian
    • View Profile
Re: Merman Fizz—Solved!
« Reply #10 on: September 07, 2017, 07:11:26 PM »
I'm actually kinda surprised. Did you sub another TL072 or a different type of op-amp? Where did you get them from?
I own madbeanpedals (duh). I am part owner of Function F(X).

Droogie

  • Electron Doctor
  • *****
  • Posts: 635
  • Andrew
    • View Profile
Re: Merman Fizz—Solved!
« Reply #11 on: September 08, 2017, 06:40:31 AM »
I subbed another 072. The one I used originally was scavenged from another build. It seems odd to me too since the voltages were good with the original, but changing it really did the trick.
Chief Executive Officer in Charge of Burrito Redistribution at Hytone Electric