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!
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.
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?
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!
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.
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.
Have you tried some different ICs? Just thinking it could be your opamps could be bad.
Quote from: Ralfg on September 05, 2017, 10:10:47 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! :)
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!
Yeah! Glad you got the problem resolved.
I'm actually kinda surprised. Did you sub another TL072 or a different type of op-amp? Where did you get them from?
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.