sunking troubleshooting

[pewtershmit]

hi everyone. My Sunking is experiencing an issue. The Gainpot isn't acting as it should, when I turn the pot clockwise, there isn't much of a change, just some high end going away. The lug wiring is correct and I don't believe there are any faulty wires. So how can I go about troubleshooting this? I guess the first step would be to see if the pot is defective? The tone and volume pot seem to be working as it should. There is also a crackle when engaging the pedal on but I think this may be due to a faulty DPDT switch.

[madbean]

Can you give us some voltage readings of the pins of the three ICs please? Have you used any parts substitutions anywhere? Also, have you tried it without the DPDT switch?

[pewtershmit]

IC1
1 4.80
2 4.80
3 3.70
4 0
5 4.8
6 too cramped to touch the pin with my multi
7 too cramped to touch the pin with my multi
8 9.56

IC2
1 4.91
2 4.80
3 4.79
4 -9.29
8 17.30
7 4.71
6 4.81
5 4.80

IC3
1 9.56
2 4.74
3 0
4 -4.68
5 -9.28
6 4.93
7 7.25
8 9.56


I did use some parts substitutions c14 I believe is a 3n3 not 3n9 and c12 is a 22n. Thats what I can remember for now. I do no know how to wire it without the switch, just bridge it somewhere?

[madbean]

The voltages are good. So, I think a faulty component. One last thing...are there any voltage changes on any of the pins on IC1 or IC2 when you adjust the gain pot?

[pewtershmit]

The voltages are good. So, I think a faulty component. One last thing...are there any voltage changes on any of the pins on IC1 or IC2 when you adjust the gain pot?

Thanks Brian. I do not see any changes to the IC voltages when turning the pot. Could the pot be defective? 

[pewtershmit]

Ive taken a picture! hopefully I made a simple mistake  that we can all laugh at and learn from.

[jkokura]

Note to Brian, perhaps you or someone around should put together a sticky on Debugging for this forum (I'm willing if you give me the go ahead, but no promises on perfection!)

To the OP. It looks to me like you're going to need to put together an audioprobe. It can be as simple as some wire and a cap, so no worries. Google it, or check our DIYstompboxes for more info.

Audio probing is the best debugging method I know of. If your voltages look right, your wiring looks right, you can't see any wrong or backwards parts, and it should be working, an audio probe will help you find where the signal dies. Once you know where the audio signal dies, you will have a good idea what part might be causing the problem. If I were you, I would start audio probing from the output and work back towards the input until you have signal. Once you have signal, you will have an idea of where the problem is. Try resoldering some joints and double checking the values/orientation to make sure they're correct, perhaps even replacing a suspect part.

Hope that helps. I should look for a good thread or perhaps make a tutorial on what an audio probe is and how to make one/use one...

Jacob

[gtr2]

I'm afraid to build a sunking as it seems these seem to cause the most problems along with the dig dug and aquaboy...

[jkokura]

don't be afraid! Just because it causes problems doesn't mean that it's not worth trying to do. When the parts count goes up, and the complexity is a little larger, things don't always work right. With a little planning to start, and an audio probe, you can almost always be sure it will work in the end.

Jacob