Tubescreamer debug, gain and volume knob not working

[afrogoose]

Hey Everyone!

Like the subject says, I've built a(nother) Tubescreamer,and when engaged it seems to merely pass the signal unaffected.  The tone knob does work, but the gain and level knobs do nothing.  I'm a bit frustrated and in the dark at this point, and I'm hoping some of the more expert experts might have a suggestion on where I should be shining my intellectual flashlight. 

Specifically this is an Eternity which is to say it's a Tubescreamer without the in and out buffers,or a Son of Screamer with out the "Son" or "Screamer." I also wired an offboard dpdt switch for the clippers which have 3 si diodes and 2 LEDS.

Thanks!!!
Andy

 

[jkokura]

Have you seen the debugging thread? If you give us the details that thread helps you provide for us, it will be much easier for people to give you any help. Right now you've given us a vague detail at best, meaning that it could be anything.

Typical problems include: Bad offboard wiring, defective or broken parts, mis-soldered or badly done joints, backwards or reverse orientated parts, a bad powersupply or other offboard problem... The list is so big that we need more specific details. Give us those details and we'll do our best.

jacob

[afrogoose]

Thanks for the advice Jacob!  Here goes...

Circuit: Eternity/Tubescreamer sans in and out buffers

Link to Schematic : http://www.gitaarnet.nl/forum/showthread.php?t=130252

I built it on a circuit board I bought on the 'net.  I built it exactly to spec (or so I think?) with the exception of an off board dpdt switch which has si diodes - nothing - LEDs.
I'm also using a .1uf input cap until I can get the proper value (.055uf)

Problem : When engaged, the pedal doesn't effect the sound, it just passes the signal "clean."  Also, neither the gain or level knobs work.

The battery I'm testing it with reads @ 9.5v
I have the battery hooked up to a DC jack but it seems that I'm reading 9.03v where power comes into the board.

IC Voltages:

P1 : 4.27v
P2 : 4.27v
P3 : 3.87v
P4 : 0.0v
P5 : 4.24v
P6 : 4.24v
P7 : 4.24v
P8 : 8.57v

DPDT switch:

si diodes : 4.27v and 4.21v
no clippers/middle : 4.21v and 4.21v
LEDS : 4.20v and 4.20v

Thanks again!!! I appreciate any and all insight!!
Andy

[jkokura]

Without pictures I can't tell you for sure, but the numbers look good, and even with a drop of .5 V, the 9.03V at the board is good to run the circuit.

How closely have you inspected the board? Are you sure you have all the right parts in all the right places? Have you got everything oriented the right way? Have you looked really, really closely to see if you have any solder bridges? The reason I ask is since everything number wise seems pretty good, if the clean input signal is jumping to the output before going through the circuit it might do what you're describing.

Is it the madbean board you're building from? can you get us some really good closeup pictures of the board?

jacob