Egodriver Problem

[tenwatt]

Out of curiosity I pulled the IC out of the socket and measure R14 and everything was fine.  Socket?

Did you measure R14's value or did you measure the voltage?

If the voltage is fine, that indicates to me that either there is something wrong with the socket, or it's a problem with the IC. If you've measured the value, you can't rely on your measurement if the part is still in the board. As long as the bands are correct, you don't need to worry about it much.

Sorry man, it's tough sometimes. I've had many things go wrong with my builds, and it can be very frustrating indeed. You might just need to take a break for a few days or even a week or so. If worst comes to worst, I'll get it working for you if you send me the board.

Jacob

I measured the voltage.  Couldn't it also be something on the other side of the IC?  If I remove the IC and R14 voltage wasn't funky it could be anything from the IC or behind it?  Tonight I'm going to take voltage readings on EVERYTHING with and without the IC.

[tenwatt]

Here are all the readings:

R1 - 1.6mV/0mV
R2 - 4.26V/4.26V
R3 - 4.46V/4.26V
R4 - .1mV/.1mV
R5 - 4.46mV/4.46mV
R6 - 4.46mV/4.46mV
R7 - 4.46mV/4.46mV
R8 - .1mV/.1mV
R9 - 2.1mV/2.6mV
R10 - 1.3mV/1.3mV
R11 - 1.2mV/1.2mV
R12 - 9.25V/9.25V
R13 - 9.25V/8.85V
R14 - 8.85V/4.46V
R15 - 4.46V/.1mV

C1 - 4.26V/.3mV
C2 - 4.46V/4.46V
C3 - 4.46V/.3mV
C4 - 4.46V/4.46V
C5 - 4.46V/4.46V
C6 - 4.46V/.2mV
C7 - 4.46V/.8mV
C8 - .6mV/.1mV
C9 - 8.85V/.1mV
C10 - 4.46V/.1mV
C9 - 8.85V/.1mV

D1 - 4.46V/4.46V
D2 - 8.85V/.2mV

Q1 - 4.46V/4.46V/4.46V
Q1 - 4.46V/4.46V/4.46V


IC:

1 - 4.44V
2 - 4.44V
3 - 4.24V
4 - .1mV
5 - 4.44V
6 - 4.44V
7 - 4.44V
8 - 8.86V

[madbean]

Everything looks right as far as voltages. Pretty much what I would expect.

R1 and R9 looks suspect on the build but I'm having trouble reading the values. Can you list the band colors for those two? I can't see them clearly. They should be a 1M and 150k, resp.

[tenwatt]

Everything looks right as far as voltages. Pretty much what I would expect.

R1 and R9 looks suspect on the build but I'm having trouble reading the values. Can you list the band colors for those two? I can't see them clearly. They should be a 1M and 150k, resp.

R9 is pretty clearly Brown, Green, Black Orange, Brown (150k)
R1 that is weird.  I can't tell what the third band is.  It's obviously Brown, Black, ?, Yellow, Brown.  The "?" isn't clear.  It's not black, like the band above it.  It seems to be silver or grey.

[madbean]

Try measuring R1 in circuit with your DMM. We are just looking for ballpark, not an exact value.

[gtr2]

On my color band calculator that silver band gave R1 a 1.08M value as listed previously in the post.  I do remember it coming up with some unconventional value warning though 

Josh

[tenwatt]

Try measuring R1 in circuit with your DMM. We are just looking for ballpark, not an exact value.

1.009M

[gtr2]

I wouldn't think that would cause your problem anyways, its just a pull down resistor.

[tenwatt]

Any other ideas?  I feel a lack of confidence to start another project until I figure out what I screwed up on my first.

[madbean]

I wouldn't think that would cause your problem anyways, its just a pull down resistor.

If it were defective or somehow a very very low value it could alter the input impedance of the op-amp which could lead to oscillation with enough gain (I'm guessing).

[madbean]

Any other ideas?  I feel a lack of confidence to start another project until I figure out what I screwed up on my first.

Have you tired using a smaller value for the gain pot? Say, 500k...audio or linear.

[tenwatt]

Any other ideas?  I feel a lack of confidence to start another project until I figure out what I screwed up on my first.

Have you tired using a smaller value for the gain pot? Say, 500k...audio or linear.

Nope...thought about it but didn't do it.  I have a A500k.  I'll try it tomorrow.

[madbean]

Another shot in the dark is that it could be the 2n7000s have a different pinout than normal. Can you tell who is the manufacturer? There should be some markings on the faces of those transistors.

[tenwatt]

Another shot in the dark is that it could be the 2n7000s have a different pinout than normal. Can you tell who is the manufacturer? There should be some markings on the faces of those transistors.

I put the A500k in and there was no change in the problem.  It's weird because the pedal sounds GREAT until the gain hits about one o'clock then it starts spitting ans stuttering.

Here's a pic of the transistor:

[bigmufffuzzwizz]

Any other ideas?  I feel a lack of confidence to start another project until I figure out what I screwed up on my first.

I urge you not to give up. If you can't get this one going, I think you should get another one. Maybe something simplier to give you some more building confidence. I flopped up on my second build and I spent 6-8 months trying to figure out what was wrong. Never solved it and it almost caused me to quit altogether. I'm glad I didn't cause that was the only build I screwed up so far. If you plan on building more than one pedal this is what is gonna help you understand how they work. Plus you can always come back to this build when you have more experience and knowledge.