Yellow shark - no gain

[Tanaka]

Hi there,

I am really sure a newbie, and I can't understand something :

I heard a yellow shark before and I like it a lot. So, i decide to realize one by myself .

I tried but I have a really differnet sound with no "power" at all and no gain . The pot vol and drive seems to be the same job .
So, i decide to try with another one, because I can't repair the first one .
But I have exatly the same thing again and ... one more time !!!!!!!

I have 3 yellow shark that I can't call like that . They do exactly the same things and I dont' know why !!


Question:

which component cause something like that ( no power ( really few volume ) and no gain ( no distorsion at all )

Thanks

T.

[Sigesmundninja]

You should post some pictures of your populated board and the wiring. Both component- and solder-sides. Someone here will surely be able to help you out.

Allso list any subs you might have done.

[mgwhit]

+1 for what Sigesmundninja said: good photos and list any substitutions you've made.

The fact that you've had three all turn out the same does suggest you've got an incorrect component somewhere, and I think the most likely culprit would be R14, which should be 51R (i.e. 51 Ohms).  make sure you don't have a 51K there.  Mistaking R for K is probably the most common accident around here, and in this schematic it could lead to incorrect voltages on both your op-amp and your JFET.

Which reminds me: please post your IC and JFET pin voltages.  That might help more than anything.

And are your D1/D2 LEDs lighting up when you play hard with the Drive knob cranked up?  If not, we can assume that the problem is occurring at or before the op-amp.  Good luck!

[Tanaka]

Thank you guys !! You're really helpful .

I'm really a newbie , as i said .. i can't take measurement ( i have digital multimeter but i don't know exactly how to use that )  .

some news may help :

- I didn't modify the project or components
- the green leds doesn't lighting up .. never
- the volume and drive pot seems to do the same job


I have a little volume, but no gain at all , with the volume and drive gain at 100%.

If you guys have patience and tell me how to measure the ic, i can try that ... So, I learn something new !

Thank you so much !!

ps: If i can, I post photos ( I have no camera, just the cell )

T.

[mgwhit]

Did you triple check your R14?  I still think that's the most likely culprit (and a simple fix if it is).

The fact that your D1 and D2 aren't lighting up, you have no clipping, very low output volume and your Volume and Drive knobs are indistinguishable suggest that your op-amp is amplifying, but not enough to actually clip.  That suggests low voltage on the op-amp IC or something monkeyed up in the input of your board.

Again, have you checked your R14?

Here's how you test voltage with a DMM.  Set your DMM to the most appropriate DC voltage test setting -- greater than the voltage you're testing for, but not ridiculously higher.  On my DMM it's 20VDC.

Connect the black lead to a ground point.  If you've got alligator clip leads, this is very simple -- just clip it to the ground point on your power jack.  Otherwise, you just need to hold it against the ground point, but that's harder than it sounds.  You'll inevitably lift it while you're taking a reading.  So if you do it that way and you get a strange reading, go back and make sure you still have ground contact.

Now touch the red lead to any point you want you want to read the voltage at.  Test the voltage right at the DC jack, where your power wire connects.  Now test it at the board 9V input point.  Test it at the positive legs of C13 (VC) and C14 (your op-amp reference voltage).  Now test all the pins of the IC (which are numbered 1-8 starting just to the left of the dimple and continuing in a counterclockwise direction).  Now test the Drain, Gate and Source pins of Q1.

Post those voltages here and you'll get some good help.  But please check your R14 first.  Good luck!

[Tanaka]

Thank you !!!!

ok i have the values as you can see in the picture .

I check R14 and is a 51R for sure .

Many many thanks !!!


T.

[mgwhit]

Hmmm.  I don't have this board myself, so I can't check, but the voltages look like what I would expect to see on IC1 pins 2, 3, 4, 6 & 7, and Q1.  I think you may have the voltages for C13 and C14 swapped on your diagram, but we can work with this.  Thanks for posting these.

Since your voltages look correct and your symptoms point to a problem at or before the drive stage, I think you need to triple check all of your components (a.) from the board input into the op-amp input (R1, C1 and R3), and (b.) in the op-amp feedback loop (R4, R5 & C3).  R1 and R5 are the ones I'm especially interested in, but please triple check them all.  A low value for R1 would send more of your input signal to ground before it hit the op-amp, and a high value for R5 would lower the gain of the op-amp stage.

[Tanaka]

Thanks a lot mgwith !

I checked out of current :

R1 = 1M
R3 = 15k

R4 = 3k
R5 = 1k

I don't know how to check the capacitors C1 and C3 ; there's a way to do that ?


Thank you so much, again and again ..

T.

[mgwhit]

I'm sorry -- I really meant just visually check the color codes on the resistors and the marked capacitor values.  I'm glad you knew to measure with the power disconnected.  There is no effective way (that I know) to measure capacitance once a capacitor is in-circuit.

Confirm that R7, R9, C7 and C8 are the correct values, and that your Drive pot and Nature pots are accurate and functional.  Use a DMM to test that all your ground points have proper continuity to ground.  Beyond that, I think you're going to need to build an audio probe (not as hard as people think) or post some photos.  Are you using a CA3130EZ?

I've got to admit that I'm running out of ideas.  Maybe someone else will chime in here.  Good luck!

[Tanaka]

So many thanks, really .

Confirm that R7, R9, C7 and C8 are the correct values, and that your Drive pot and Nature pots are accurate and functional.

Yes, i can confirm everything : correct values for capacitors and resistors and pot ok ( tested with DMM ) ...

Are you using a CA3130EZ?

No: CA3130

Use a DMM to test that all your ground points have proper continuity to ground. 

I'll do that one more time ( I have already checked , but maybe I missed something ....

I think you're going to need to build an audio probe (not as hard as people think) or post some photos. 

I don't know what is that ... have you a link or something ?

I've got to admit that I'm running out of ideas.  Maybe someone else will chime in here.  Good luck!

Well, again, really really thank you for your support .  I don't speak english very well and I'sorry that I can't explain how much I had appreciate your courtesy .


T.

[mgwhit]

Here's a link to a site that shows pretty well how to make an audio probe.  All you really need is a mono (or stereo) jack, some wire, an alligator clip an a capacitor that's big enough to pass most of the frequencies in your guitar signal (100n-10u).

Once you've built it, plug your guitar into the effect circuit input.  Then, instead of plugging into the effect circuit output, run a cable from the probe jack to your amp.  Connect the probe's ground wire to a ground point and touch the tip of the probe to various points along the circuit's signal path while you or someone else strums the guitar.  Turn your amp down pretty low because when you probe a point after an amplification stage you're going to get a crazy loud signal before it has been tamed by the Volume pot.

You'll have to understand the circuit pretty well to use the audio probe effectively, but you can learn a ton using one of these and working through a board or two.  Of course, if the signal just isn't being amplified by your op-amp, you're back where you started, but at least you'll know.

[Tanaka]

Thanks mgwhit,

I'll try that .


Cheers,

T.

[Tanaka]

I just found the problem ... I don't know if I'm happy or sad because it was my fault ..

I just made a mistake in R2 : 360ohm instead of 360k !!

I buy 20 of these without check and that's why I have the same problem on three pedal ...

Thanks to who try to help me !!!!


T.