Screamer clone help

[crowsmith8]

Hi, I'm building a screamer clone and am have a ton of trouble.  I recieved the board from BYOC and sourced all the parts myself.  Currently what is happening is that when the pedal is engaged I get nothing but hiss.  If I turn the drive, volume, or tone knobs the amount, intensity, volume, and tone of hiss change, but I don't get any guitar, unless I turn my amp up to 10, and then I can just barely hear the guitar.  The LED lights up and I also get full signal in bypass.  I used my meter to take some readings and got these values at the op amp
1=5.5
2=5
3=1.5
4=2

8= 8.2
7=5.5
6=4
5=3

I started a thread over at the BYOC forum, but have not had much luck with those guys, although they did point out a few things that needed to be fixed (but none of them were the solution).  Here is a link to that thread. 
http://board.buildyourownclone.com/viewtopic.php?t=469  It has pics and details of what I've tried so far.  Please help, I'm at wits end with this build, I just can't seem to figure out what's wrong.  By the way I'm pretty new to all of this, so there definately could be some stuff I'm overlooking.  Any help would be greatly appreciated.  Thanks.

[johngreene]

Pin 4 of the opamp should be 0 (ground). If you are measuring 2V on pin 4 I'd be checking your ground connections!

--john

[crowsmith8]

Thanks, John.  I'm realatively new to this like I said, so I just wanted to double check.  Are the ground connections just on the jacks and switch, or should I be looking on the circuit board for ground too?

[johngreene]

If you wired it to be ground switched by the input jack then you should have ground on the input jack when something is plugged in and it should be the same ground as on the circuit board. All the grounds should be connected.

--john

[markm]

Maybe double check your soldering for possible solder bridges or,
maybe one of the tants is incorrectly installed......
just a shot in the dark for me

[crowsmith8]

I have checked for solder bridges many times and I don't think I have any.(not saying that I missed one, I will definately check again, in fact it is the first thing I do every time I sit down to troubleshoot this pedal, just in case a pair of fresh eyes can catch something I missed earlier)

What I gather a tant is from searching is that it is a polarized caps, is this correct?  If so, I have checked those many times as well and they are all in right.  If I'm wrong as to what a tant is please correct me so I can check them and know for future knowledge.  Thanks.

[gaussmarkov]

as discussed, pin 4 should be 0v.  pin 8 should be the same as your battery and the rest should be quite close to half the battery voltage.  so, please tell us your battery voltage.  also, take voltage readings on the collector, base, and emitter of each of the transistors.  the collectors should also be at battery voltage and the difference between base and emitter should be around .5 or .6 volts.

in addition, please build an audio probe (as described in the debugging page linked at the top of all diystompboxes.com pages) and use it to figure out where your signal disappears and where the noise begins.  when you touch the audio probe to the input, you will hear your guitar as in bypass mode.

having said that, i am wondering whether you can get a hold of a tubescreamer schematic and match that up with your pcb?  have you seen the schematics and accompanying layouts provided by generalguitargadets.com and tonepad.com?  the audio probe will be difficult to use if you have difficulty following the signal path on your pcb.

--gm

[crowsmith8]

Thanks for the advice.  I'll look into getting a schematic, building an audio probe, and then following the signal through my pcb as soon as I get off work.  I'll also get the readings for my transistors.  I have a pretty fresh battery hooked up right now, so I'm getting a little less than 9volts from the battery.  I'll let you know how it goes.  Thanks.

[crowsmith8]

Well, I was able to solve the problem with a little help over on the BYOC board.  It turned out that there was a blemish on the board that I knew about the whole time but had forgotten all about.  Boy do I feel dumb.

But I did end up making the audio probe and learning a lot about the circuit.  That thing is so cool, and a great troubleshooting tool.  All in all this has been a huge learning experience for me, even though there was a ton of frustration.

Thanks for all the help.  I really appreciated it all.

[gaussmarkov]

sweet!  and don't feel dumb ... this happens to everyone.  and it has a good side to it that you just described.  you can learn a ton from somethiing that is not working -- including stuff that has nothing to do with the fix.