tube screamer hum

[aleos]

I've built my ITS8 from guitar gadgets and instead of screaming it's humming.
Humming like crazy.
I get a perfect signal when effect bypassed.
LED lights up when engaged, but my signal becomes very weak and CRAZY humming starts . Humming is controllable by the volume knob. But humming to signal ratio is crushing.

Is this a ground problem?
I'm using a negative tip boss adapter. I don't have a battery right now but I'll check with that later.

thanks for the help.

Aleos

[R.G.]

Yes, it's a ground problem. (re)check your wiring.

[m-theory]

Tube hummer...sounds like a title for a porno flick.   

[aleos]

I've rechecked my wiring and I'm sure that it's fine.

Are the two clipping led's supposed to light up? Because they are not.

I'm baffled why this isn't working, I really took my time and was very meticulous.

I'm a bit of a multimeter amateur so help me out. What is the best way to trouble shoot for this problem using a multimeter?

thanks alot

Tube hummer...sounds like a title for a porno flick.   

it does dosen't it?

[MikeH]

The clipping LEDs should light up when you strum, although not as brightly as you may suspect.

Follow the protocol in the "Debugging: What to do when it doesn't work" sticky thread.

[aleos]

well first off, I'm getting a reading of about 2.1 at the power supply. With the adapter AND with a fresh battery.
I assume this will alter all the other readings so I won't bother putting them up. When I disconnected the wire that connects the board to the power supply then I got a reading of around nine from the power supply.
I'm getting confused.
And the internal leds are not lighting up at all.
thanks for all the help.

Anyways here are the ic readings.
1. 1.3
2  1.1
3  1.1
4   0.
5  2.1
6   1.3
7  1.3
8   1.3

and on Q1 and 2 readings are all lower and reflect the overall lack of power.

[Timebutt]

Seems like you should check the wiring around your 9v + connections, if you measured from + to ground you should get the exact voltage provided by the battery/adapter.
Probe around the circuit with a multimeter looking for continuity with other traces it shouldn't be connected to, look very closely to everything you have soldered because that's where the problem must be somewhere. It's a good thing to have a schematic lying next to you and work your way through the schematic, verifying with your DMM that all the parts are connected to the right other parts, and then move on to the next part until you're through.
When I debug I like to say my wiring is right, it just has to be a bad part or something: until you find a connection that shouldn't be there and you fix it up

Not sure if it would help in your situation, but I have always found an audio probe to be an incredible tool for debugging (http://www.diystompboxes.com/pedals/debug.html), you can trace the signal through the circuit and find out where things go wrong, then start looking for errors in that area.
Good luck!

[aleos]

I'm getting some continuity between the 9v and the drive 3.
I'm sorry for my lack of schematic proficiency, but should I be getting this reading?
All the other connections to the pots show no continuity.

But I checked my soldering and it's fine so I don't know why those are linking up.

here's a quick link to the schematic if anyone wants to help out a little further.
http://www.generalguitargadgets.com/pdf/ggg_its8_sc.pdf

[R.G.]

It's funny. Until they start measuring voltages, everyone checks their wiring and it's perfect. Sometimes several times. The more times it gets checked, the more perfect it is.

That's why I worded the "What to do when it doesn't work" stuff the way I did. It's important to step outside the perceptual bounds we all impose on ourself. Usually that's enough to expose what we could not see.

[aleos]

I just read this in the "what to do when it dosen't work" thread

"or if it makes a harsh, distorted sound only when you strum hard on the strings at full volume"

this is happening to me.
What is the common response to this ailment?

[R.G.]

The power or bias is really, really wrong. This is consistent with the voltages you read.

If you do not have 9V on the board, on the pins of the opamp, and other places where it's supposed to go, it **can not** work correctly.

Take your meter and measure the DC voltage to ground, starting at the battery clip. 9V at the battery clip? Great. Now check the other end of the battery wire, as it goes toward the board. Follow that wire, checking voltage at each place you can get the probe onto a connection. When you find the place where the last connection was 9V and the current one is 1.3V, you have just passed the problem.

[aleos]

If you do not have 9V on the board, on the pins of the opamp, and other places where it's supposed to go, it **can not** work correctly.

I can't get 9v anywhere on this project to save my life. Everything is reading around 2.1 or 1.3.
My dc jack is fine because, as I mentioned above, when I disconnected the wire to the board I did get 9v at the jack.

[sed]

A question about the layout from GGG. D5 isn't included in the layout. I suppose that is in the schematic to protect against reverse polarity of the power supply. I don't know if D5 can have anything to do with the V+ problem but I think it's funny that it's left out in the layout.

[aleos]

i think d5 is there in the layout.
bottom right corner?

edit:

funny just after I made this post, I went to my workbench to take some readings and D5 started smoking. And I don't mean havana cigars.
Would have this been the problem? Would this diode being faulty have contributed to the symptoms I listed above? Did my diode burn out for another reason related to my initial problem?
Can I do any more testing before I order and receive a new si diode?

thanks everyone for their help, I'm learning alot, thanks for your patience.
I guess this pedal isn't making it to the show on sunday.

[aleos]

I also just noticed that the illustration of the diodes on the wiring and component layout

http://www.generalguitargadgets.com/pdf/ggg_its8_lo.pdf


indicates the black stripe in the square trace. This contrary to what I've usually seen. Is this just a typo?

I just replaced the burnt out diode with a new (verified working) one, it burnt up as well.

[R.G.]

If you do not have 9V on the board, on the pins of the opamp, and other places where it's supposed to go, it **can not** work correctly.

I can't get 9v anywhere on this project to save my life. Everything is reading around 2.1 or 1.3.

That's a real problem. Mother Nature is telling you that something is installed improperly on the board or that there's a solder/wiring problem.

funny just after I made this post, I went to my workbench to take some readings and D5 started smoking.
...
Would have this been the problem? Would this diode being faulty have contributed to the symptoms I listed above? Did my diode burn out for another reason related to my initial problem? Can I do any more testing before I order and receive a new si diode?
...
I also just noticed that the illustration of the diodes on the wiring and component layout
indicates the black stripe in the square trace. This contrary to what I've usually seen. Is this just a typo?

It's not a typo.

D5 is the polarity protection diode, I believe. It's inserted with its stripe (cathode) on the +9V line and it anode (arrow) on the ground line so that when a backwards power supply is connected, it will hold the reverse voltage to 0.7V.  If you leave power on it a long time, it gets really, really hot.

The question then comes up: did you install D5 the way the parts placement shows (which is correct) or backwards? If backwards, that may be your entire problem.

[aleos]

The question then comes up: did you install D5 the way the parts placement shows (which is correct) or backwards? If backwards, that may be your entire problem.

I installed it with the black stripe in the circle.

D1 and D2 are also labeled in this backwards fashion in the layout. But in the instructions, where there is a photo of an assembled board, D1 is inserted in the "proper" blackstripe-in-the-circle fashion.
(sorry for my baby talk and lack of correct terminology)

[aleos]

WHoooo hooo. Backwards backwards diode. Who would've thought.
I'm getting nine volts, no hum and great overdrive!

Thank you all, for your expertise. 

[R.G.]

Congrats! You got it!

You can use it without D5 for a while, just be careful wth battery polarity until you get another one in there, or you might have to replace the opamp too.

[aleos]

I actually had a few leftover from a previous project gone bad, so there's a new one in there and pedal will be playing jazz as of sunday.