BYOC Bass Overdrive (DIY Clone) Fade in issue

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codysorgenfrey
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Post by codysorgenfrey »

Hello! I'm working on finishing my first build and I've got the effect so close to working perfectly but I've run into this one issue that I can't seem to figure out and was hoping someone on here could point me in the right direction!

The issue is that when I switch the pedal on, the signal fades in from silence over about a second (which is a long time, I know). The interesting part, and where I'm having an issue figuring out what's going on is that this doesn't happen all the time. The overdriven signal doesn't fade on, so if I have the blend pot set all the way to the "wet" side, the effect turns on instantaneously like it should. If I have the blend pot turned all the way "dry" is fades on from silence.

This leads me to look into the parts of the board dealing with the dry signal. Using an audio probe I listened at various points on the board while turning the effect on and off and here's what I found:
  • Pin 1 of IC1: No fade.
  • Pin 7 of IC1: No fade.
  • Pin 2 of Q1: No fade.
  • Pin 1 of Q1: Fade on.
So I swapped out the transistor (I originally used a 2N3904) to a 2N5088. The problem still persists.

So I reflowed the solder joints for C12. The problem still persists.

Any thoughts on what could be happening here? Should I replace C12? The fact that it fades on over time makes me think it's a capacitor.

Thanks in advance for any help! I've included pictures of the build, the schematic and the layout of the PCB here: https://1drv.ms/u/s!AgoaZE5BhY1vgZ1J3T3 ... g?e=CacoD7

PS: I know one of the wires for the A1M pot is disconnected, it broke while taking the pictures :(

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lykwydchykyn
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Post by lykwydchykyn »

Sounds like maybe some DC leaking into the output somewhere. Have you checked for DC on the output?

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phatt
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Post by phatt »

Hum,, well going by the pics of layout, C13 is not connected to anything,
same for R19, R3, pin5 of IC2b,
Pin4 of IC2 has no ground connection trace,
blend pots are missing a connection to bias,, and and and,
You are missing com points as well as no bias.
you will likely have to start all over again.

I assume you are designing this so go back to Schematic and double check all connections. I believe most Cad stuff has design rule to check all connections,, USE IT.
I'd be rethinking the layout of your tracks, try and avoid really close tracks. you can spend hours staring at pcb layouts trying to work it out. :slap:
And I NEVER use auto trace connect as it does some really wacky layouts if you don't setup DESIGN Rules BEfore you start. :secret:
Phil.

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codysorgenfrey
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Post by codysorgenfrey »

lykwydchykyn wrote: 22 Jul 2022, 21:40 Sounds like maybe some DC leaking into the output somewhere. Have you checked for DC on the output?
No I haven't checked! Once I rewire this pot that broke I'll check and report back. Thanks!
phatt wrote: 23 Jul 2022, 05:09 Hum,, well going by the pics of layout, C13 is not connected to anything,
same for R19, R3, pin5 of IC2b,
Pin4 of IC2 has no ground connection trace,
blend pots are missing a connection to bias,, and and and,
You are missing com points as well as no bias.
you will likely have to start all over again.

I assume you are designing this so go back to Schematic and double check all connections. I believe most Cad stuff has design rule to check all connections,, USE IT.
I'd be rethinking the layout of your tracks, try and avoid really close tracks. you can spend hours staring at pcb layouts trying to work it out. :slap:
And I NEVER use auto trace connect as it does some really wacky layouts if you don't setup DESIGN Rules BEfore you start. :secret:
Phil.
That'd be awesome if the effect still worked with all these problems :lol: I have pours for GND and VA, sorry I didn't hit ratsnest before uploading the images. They're in the folder now as well.

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codysorgenfrey
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Post by codysorgenfrey »

lykwydchykyn wrote: 22 Jul 2022, 21:40 Sounds like maybe some DC leaking into the output somewhere. Have you checked for DC on the output?
After getting back to this there is unfortunately no DC signal leaking into the output :(

I went ahead and replaced some of the caps anyways (c10 and c11) but that didn't do anything. Which makes sense, they seemed to be working correctly anyways.

It's gotta be something up with the transistor since that's where the problem is first heard and under other settings everything is working correctly. I'm not super familiar with transistors so I'm going to read up and see what I can find. Any further suggestions or pointers would be greatly appreciated!

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x-tn
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Post by x-tn »

codysorgenfrey wrote: 22 Jul 2022, 17:14 ...Using an audio probe I listened at various points on the board while turning the effect on and off and here's what I found:
  • Pin 2 of Q1: No fade.
  • Pin 1 of Q1: Fade on.
So I swapped out the transistor (I originally used a 2N3904) to a 2N5088. The problem still persists.
Which one is 'Pin 1' of Q1?
If there is no problem on 'Pin 2' (base?) of Q1 then there is a problem wth the Q1 or the circuit around it. Measure the R17 value and confirm it's 360ohms. You can measure and confirm R14, 15 ,16 values, too.

Also, I see you solder wires inside the pot rivets. It's not a good idea. You might damage the pots by heating the rivets.

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codysorgenfrey
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Post by codysorgenfrey »

x-tn wrote: 02 Aug 2022, 17:30
codysorgenfrey wrote: 22 Jul 2022, 17:14 ...Using an audio probe I listened at various points on the board while turning the effect on and off and here's what I found:
  • Pin 2 of Q1: No fade.
  • Pin 1 of Q1: Fade on.
So I swapped out the transistor (I originally used a 2N3904) to a 2N5088. The problem still persists.
Which one is 'Pin 1' of Q1?
If there is no problem on 'Pin 2' (base?) of Q1 then there is a problem wth the Q1 or the circuit around it. Measure the R17 value and confirm it's 360ohms. You can measure and confirm R14, 15 ,16 values, too.

Also, I see you solder wires inside the pot rivets. It's not a good idea. You might damage the pots by heating the rivets.
Thanks! I did indeed ruin on of the pots by soldering it that way! Lesson learned.

So some good news and some bad news! The good news is I got the problem with the fade on all sorted out. The bad news is there was no problem with the pedal this whole time... :lol:

After deciding to breadboard just the problem area of the circuit the same problem was happening! Then I decided to breadboard just the LPB-1 circuit! Still happening! And it's like the most simple circuit so I was sure it was put together correctly! Which led me to look into outside factors... Then I found the big issue.

My effect tester box I was using this whole time was wired so that when the effect was bypassed it also disconnected the effect from ground. I did this intentionally thinking that it'd be a good idea to have the effect completely off when not using it. But I unintentionally made it so that when trying things like bypassing the effect, it has no power... thus the fade on. I'm actually quite surprised it had no problem with this when the blend was set to fully wet :roll: After rewiring the effect tester box there is no more problems! Now I can box this thing up and enjoy it!

Thank you so much everyone!

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