The Scream - Issues

[pjmaclean]

I'm hoping someone can advise what I do to test and diagnose a problem on my build of The Scream.  All voltages are correct per the document, however the pedal seems to be acting more as a clean boost.  There appears to be no clipping.  The pedal is dead quiet and all functions seem to work except for the Drive and SLR.  The diodes  are installed in the correct directions, but I'm wondering if I installed the LED's the wrong way.  That's the only thing I can think of and was hoping someone could help me diagnose the problem.  Any help would be appreciated.

Thanks

[jimilee]

Close up clear pictures of both sides would be a huge help, and why don't you go ahead and post those voltages. Have you reflowed all your joints? I still have to do that from time to time.


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[Aentons]

From the VFE website: "There is an internal DIP switch that sets whether 12:00 is clean or crunchy (via LED clipping),"

How is your internal dip switch set on the LED side? If it is in OFF(down) position, then it will be a clean boost when the SLA(clipping) knob is set to noon.

[gordo]

Those tiny solder pads are sticklers for accurate soldering too.  Like Jimi said, it's likely a sketchy solder joint or a bridge.

[pjmaclean]

Of course I boxed it. and had to unbox it.
I'll unbox it and send the pictures.
DIP switch 1 is off and 2 is on

I did notice a bad solder joint on the ground from the switch board to the main PCB.  I reflow as many solder joints as I can reach with out having to remove the pots.
Also - I had to decrease the resolution.  The form has a 1500k limit.

Thank you so much for looking. 

[Aentons]

Looks pretty clean to me and LEDs look like they are in correctly. If you have another dual opamp, you might try that.

Also, does the Fat control work? Does the drive pot produce a volume increase when turned up?

[pjmaclean]

The Fat control does work, but the Drive - well it's not really increasing the volume.  It adds a tad bit of gain, but not what you'd expect.  The Level has to be up about 3/4 to get to unity gain.  The SLA does nothing and the internal DIP switch provides not audible change to the sound.  Weird.

[Aentons]

Hmm, not sure... I'd reflow the switch and all the silicon clipping diodes and possible the 220p cap next to pins 1&2 of the dip socket. What diodes are those and where'd you get'em?

[madbean]

Everything seems right on the build. Voltages are good, parts are in the right way and resistor values seem correct from what I see. It's a stumper.
You may have to audio probe. Specifically pin1 of the 4558 to see if you are getting the correct gain output (wondering if maybe the signal is getting mangled later on in the tone circuit).

[pjmaclean]

I found the source of the diodes.  I bought these several years ago from UTSource.  They are the rather obsolete 1S1588 diodes.  They could be suspect, but I have used them in other builds.  I tested 10 randomly and found no issues.  i.e. they all read a forward voltage of about .6 - when reversed, they all read "OL" or open circuit.  Is there any way to read them in circuit?  I attempted to and noticed, for the most part, I was getting a .6 forward voltage both ways.  I'll check those solder joints again as well as swapping out the op amp.  I don't have an audio probe, but I'll make one and let you know what I come up with.  Since I have a oscilloscope, I was going to run a 1k sine wave to the input and probe that way.  Not sure if that will tell me anything though.  Thanks again for the suggestions.