I need help debugging a Tubescreamer 808

[Sir_Ian]

Ok, I had this in another topic, but the name didn't quite describe what was inside. So, sorry to make another topic, but I don't think that one was going to do the trick. I built a tubescreamer 808, and it works in bypass, the led lights up when ON, but there is completely no sound. So here is what I got....

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Here we GOES!!!!

Here is the checklist to fill out:
1.What does it do, not do, and sound like? Works in bypass, LED lights up when turned on, but absolutely no sound.
2.Name of the circuit = Tubescream 808. From general guitar gadgets.
3.Source of the circuit (URL of schematic or project) = http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=82&Itemid=26
4.Any modifications to the circuit? Yes. I have it set set to switch between regular diode clipping and LED clipping. I also have a switch to bypass capacitor C3 (.047 uf), which is supposed to give a bass boost.
5.Any parts substitutions? If yes, list them. No....I used all the right values except for CAP C4. It says 53 pf, I used like a 49 pf. This "shouldn't" matter. I also used polarized tants for caps C5 and C9. But thats what the schematic says to do...
6.Positive ground to negative ground conversion? Nope, none of this nasty business.

9 volt power supply = 8.8 volts

Q1
C = 8.78
B = 0
E = 2.95

Q2
C= 8.79
B= 0
E= 2.96

IC1
1= 4.69
2= 5.09
3= 3.65
4= 0
5= 4.65
6= 4.66
7= 4.66
8= 8.8

to see what values I'm supposed to get, i direct you to page three of this pdf.
http://www.generalguitargadgets.com/pdf/ggg_its8_instruct.pdf

As you can see, I'm having a problem (the same problem) with both transistors. (My op amp looks like its in the ball park). I am using 2sc1815, and the collector is in the middle, so I had to bend it up around so it was at the top of the ciruit. My collector value looks correct, but I my base is 0 volts when it should be 3, and my emitter is 2.95 volts when it should be 2.5

So I think the problem is with the transistors, but really, I have NO CLUE what the problem is. The transistors might only be a symptom. I don't know...once again my first build. I'm 97% sure I orientated them right. So maybe I fried them...? I don't know how hard or easy it is. I tried to be delicate....but my knickname is Shreck...

Any help and suggestions are greatly appreciated. Thank you very much.

[bipedal]

From the info you've given, sounds like you're on the right track with the transistors being the likely problem.  (Are you using a pre-made board or your own?)

As I understand it, trannies are rather sensitive to static electricity, so it's not uncommon to have to replace them when troubleshooting a build.

Sounds like you've double-checked the pinouts -- great!.  I may be worthwhile to triple-check just in case.  Can't count the number of times I've had a build not work because I've messed up my C-B-Es...

If you haven't made one yet, consider pulling together the parts to make an audio probe -- great troubleshooting tool that lets you hear what a circuit is doing throughout the signal path.  You can track all the through -- starting at the input -- to where the sound stops to isolate the issue.

Others may have plenty more to offer you in regards to troubleshooting advice...

Good luck on resolving the issue -- it's a great feeling when a bug finally gets fixed and the gadget roars to life.   

- Jay

[frankclarke]

+1 on audio probe.

[GibsonGM]

I have some suspicions about the lack of any voltage on the bases.  Starting with Q1, trace that 510K resistor to Vr, and see that it measures about 1/2 the supply voltage.  You may have an error with the voltage divider section of the power supply, or the points marked "Vr" may not actually be going to the reference voltage? There are 6 of them. Without that voltage going to the base of Q1, nothing will work...could be a few causes of trouble here, like a solder bridge to ground or something.

Other than that, transistor pinout is suspect....and if abused enough, fried trannies.   Get that stage sorted out, then the audio probe can come into play to assure the input buffer works, and you can move on to the opamp sections.  The IC voltages look near correct, but are useless without having signal applied from the (working) input buffer BJT.   Take it in-line, 1 stage at a time...   

They are not static sensitive (that's more about FETs and MOSFETs), but TOO much voltage applied the wrong way will kill them, as will heat from over-soldering (most likely).

[chillhuman]

For me, usually when I get no sound it's because of a cold solder joint. If you check continuity b/w the legs of the different components, that may point you in the right direction.