Darkglass Microtubes B3K - Distortion not working

[guidoilieff]

I made this

Layout http://4.bp.blogspot.com/-EIyu-1z4tiE/WvSP6JVZMhI/AAAAAAAAGDE/Qny5D5tH_YQzSt-DGY826vZZUOILOHyWgCK4BGAYYCw/s1600/Darkglass%2BMicrotubes%2BB3K.png




The clean sound on the blend pot works fine, the distortion part is not working.


If I use my cellphone to play music through the pedal and jumper the 1meg resistor going to vdd (next to the tl072 on the left) I get a very "gated/starving transistor" distortion.

Using a passive instrument I get sound on pins 5,6 and 7 but nothing on pins 1,2 and 3 of the left tl072 on the layout.



All the ics voltages are ok but I don't know if the j201 are ok.

G 0
S 0.3
D 4.8

G 4.2
S 4.8
D 9



I don't know what else to say... It's not my best etching but the pcb traces are ok

[ElectricDruid]

Ok, so we need to know how far the sound gets through the distortion stages. That's quite a complicated circuit, so it's not a simple question. You'll need an audio probe to test the signal at different points in the circuit, but it sounds like you've got that sorted.

The first thing we know is that if the 'clean' path is ok, then the signal must be getting to the output of IC1A at pin 1. Please confirm this is the case.

Does it get to IC2B pin 7?

Does it get to IC3A pin 2?

Does it get to IC2A pin 1?

Does it get to IC4A pin 1?

If the answer to any of these is "No" then that's the problem, but *where* that happens tells us where to look for the problem.

HRH,
Tom

[Slowpoke101]

Check out the 100R resistor near the 4049 chip. May be the wrong value.

[guidoilieff]

Check out the 100R resistor near the 4049 chip. May be the wrong value.

Hey guess what. That was a 1k resistor. I hate 5 band color coding... Anyway, It changed nothing. I have no audio with a passive instrument.

[guidoilieff]

Ok, so we need to know how far the sound gets through the distortion stages. That's quite a complicated circuit, so it's not a simple question. You'll need an audio probe to test the signal at different points in the circuit, but it sounds like you've got that sorted.

The first thing we know is that if the 'clean' path is ok, then the signal must be getting to the output of IC1A at pin 1. Please confirm this is the case.

Does it get to IC2B pin 7?

Does it get to IC3A pin 2?

Does it get to IC2A pin 1?

Does it get to IC4A pin 1?

If the answer to any of these is "No" then that's the problem, but *where* that happens tells us where to look for the problem.

HRH,
Tom

There is audio coming from pin1 IC1A


There is no audio in any pin if I use an electric guitar/bass except from pin1 in IC1A

I think the audio first goes to Q1 and then to the rest of the ICs. Maybe that's the problem? Should I remove Q1 and jumper the gate to the drain pin?

[guidoilieff]

In the IC closest to the 4001 I have hum in pins 1, 2 and 3 like when you leave a cable connected into an amp with no instrument connected... I don't know if that sentence makes sense, sorry for my english... I leave a video to explain myself...

https://flic.kr/p/2ebGDFY

[Slowpoke101]

The effectslayout board does not exactly match the circuit diagram that you posted. Some of the IC designators (IC1, etc ) and the pins are different. So referring to the picture below what I'm about to detail should make sense.



Set the Drive, Level and Blend controls to their mid positions (half way ).

Check for audio on pins 5 and 7 of IC1. This should be at guitar signal levels. Now check for audio on pins 3 and 1 of IC1. Pin 3 should be fairly loud and pin 1 should be very loud and distorted. If there is no audio on either pin check your connections to the "grunt" switch - which really is the "attack" switch - minor error on the board layout diagram.

Now check for distorted audio on pin 3 and then pin 2 of IC4. If there is no audio on either pin check your connections to the "attack" switch - which really is the "grunt" switch - again, a minor error on the board layout diagram.

I found a schematic that was fairly close to the effectslayout board and then modified it so that it is now more accurate - maybe. This may help with following the signal path. I left the "attack" and "grunt" designators so that they match the board layout.