Egodriver LED problems

[insomniac2295]

Just got the newest version of the Egodriver PCB and I have some strange things happening. Sometimes the LED's light up a tad, then one goes out and the other one gets twice as bright. On another note, it keeps spazzing between no sound, screeching, hissing, fat and flappy, and just clean. I have yet to hear it the way it should sound. I haven't boxed it up yet. Could this be a grounding issue or something?
Checked IC, diode, and transistor orientation and for solder bridges. Everything's turned up good.
Have no fears, I just wanted to post this to see if something came to mind right away. I will post IC readings in a bit.

[jkokura]

First thing I think of is that there's ground issues. Probably in your gain section. Just a thought, it might not prove fruitful.

jacob

[insomniac2295]

IC readings:

1 7.49
2 4.57
3 3.09
4 0.01
5 9.14
6 6.69
7 5.81
8 6.91

Note: Pin 1 fluctuated quite drastically compared to the other ones. I took 10 different readings on it and got 10 widely different numbers.

[jkokura]

You should have around 9 on pin 8, 0 on pin 4, and the rest should be around 4.5 if it's setup like a typical overdrive pedal...

Jacob

[insomniac2295]

Just remeasured:

1 6.43
2 4.57
3 3.12
4 0.00
5 9.14
6 6.42
7 6.17
8 6.43

[jkokura]

Still doesn't look right.

I'd start looking at your power in and see why your power isn't getting to your IC full strength. About the only pin that's correct is pin 4.

I'm wondering if you've got the right pins on your IC - your pin 5 is what your pin 8 should be. Your pins go like this:

1 ---- 8
2 ---- 7
3 ---- 6
4 ---- 5

You really should have 4.5ish on pins 1-3 and 5-7. You should have 9ish on pin 8.

Jacob

[insomniac2295]

Whoops! I went:

1 ----- 5
2 ----- 6
3 ----- 7
4 ----- 8

[insomniac2295]

Okay so help me out here. I've never measured voltage on an IC before. Is it normal for the voltage to jump around dramatically on certain pins? If not, does that mean the IC is bad?

[jkokura]

No it's not normal, it should be steady. It probably is not harming the IC, but it indicates a problem. Work the debugging steps and check your parts, reflow your solder, etc.

Jacob

[insomniac2295]

used an audio probe to go through the circuit. The signal stops at the last pin in the TL082. Source of the problem?

[jkokura]

Depends on what you mean by the last pin of the TL082... Can you give us an idea of where you have sound based on the schematic pin numbers or part numbers?

Jacob

[insomniac2295]

Im not at home right now but I remember having sound at pin 1 and no sound out of pin 8

[insomniac2295]

also, no sound on pin 4

[jkokura]

I think you need to learn a little bit more about IC's, so here's some info:

Dual Op Amp IC's are generally setup with pin 4 and pin 8 operating as ground and Power in respectively. Then, pins 1-3 is your first stage, and pins 5-7 are your second stage. They operate by having a positive and negative input, and then an output as well. Take a look at any Dual IC (TL072 for example: http://www.ti.com/lit/ds/slos080j/slos080j.pdf - see page 4) datasheet to see the pinout in action.

In the case of the Ego Driver (you need to follow along with the schematic to understand my next part: http://www.madbeanpedals.com/projects/EgoDriver/docs/EgoDriver.pdf) you can see that the first op amp stage is used for the gain/distortion stage, and the second op amp stage as gain stage to push through the tone stack. In a tubescreamer it would follow the tone stack and act as a makeup gain stage.

Anyway, you enter the Op Amp stage 1 with the positive input on pin 3. Pin 1 is the output, and the negative input is used to drive the gain structure to give you variable distortion in the circuit. You should have audio on all three pins, with the audio on pin 1 being the connection to the next area of the circuit (in this case some clipping options). On the next stage of the Op Amp, we enter in the positive input pin 5 and ouptut on pin 7. Pin 6 connects to your output to create a non-variable gain stage and push your signal to your output through the tone section.

Pin 8 is directly connected to the +9V after R12 steadies the power in. Pin 4 is directly connected to Ground.

So, if you're using an audio probe, your real output should be pin 7 of the IC. If you have what sounds like great guitar sound there with a working drive knob, your problem is after that in your tone and volume sections. If it doesn't sound good or you have no sound there your have a problem in your gain section or the clipping section between stage 1 and 2 of the IC. If it sounds bad, move backwards ad listen at pin 1 and/or pin 5 of the IC. If it sounds good move forward and listen at pin 3 of the volume pot.

Also note that if you're using the new layout/PCB that was just released that you need to make a mod to make sure the clipping switch works properly - look at the build docs for details on that one.

Jacob

[insomniac2295]

Jacob, I am now 100x smarter that I was before. Thanks for your knowledge and I shall report back!