JD-9 single sided Oscillating issues

[jimilee]

I made a layout for the Ibanez Jet Driver. It works, but I'm getting some oscillation in either the Drive or EQ section. I can't quite work it out. My voltages all look like they're supposed to. Any help is much appreciated.

[jimilee]

Just a bump to see if anyone can see something in the layout that would cause the oscillation.


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[mauman]

I'm thinking you may have a too-long trace (adding too much inductance) connected to your lower op amp (EQ) pin 6 (inverting input.)  It runs all the way to the top of the board to pick up Mids pot 1 and Tone pot 1.  Feedback loops might need to be shorter than that, stray inductance or capacitance there can cause oscillation.

[jimilee]

I'm thinking you may have a too-long trace (adding too much inductance) connected to your lower op amp (EQ) pin 6 (inverting input.)  It runs all the way to the top of the board to pick up Mids pot 1 and Tone pot 1.  Feedback loops might need to be shorter than that, stray inductance or capacitance there can cause oscillation.

That makes perfect sense; I'm still learning. I modified the original schematic, and now I think I know what it was the way it was. Thank you sir.


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[NorthCoast]

Did you include C101?

The 47uf cap is C100, which is 100uf on the schematic, but I don't see a 47uf C101.

Also, it looks like there might be two traces that are touching that shouldn't; I've circled them in yellow:

[jimilee]

Did you include C101?

The 47uf cap is C100, which is 100uf on the schematic, but I don't see a 47uf C101.

Also, it looks like there might be two traces that are touching that shouldn't; I've circled them in yellow:

I checked with my meter, the traces aren't touching, so we're good there. The 100uf is actually attached to my +9 and ground leads on my testing rig. That did kill a lot of the noise. I'm going to rework it with shorter traces in the top section, I think that might do it. I reworked the original schematic because it seemed to be all over the place, but it seems they may have been a reason for that madness.


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