mk2 trouble shooting!

[tacobender]

So I went all out got old school caps resistors etc. I wired it with a bias knob, which I've never done before. And moved some of the grounds around from the origional design. But now it plays in bypass, but when its activated all I get is a faint distortion with the amp up about half way
Any ideas where I might have went wrong?

[antonis]

No idea w/o schematic (including mods - especially those "moved" grounds..) 

[LightSoundGeometry]

So I went all out got old school caps resistors etc. I wired it with a bias knob, which I've never done before. And moved some of the grounds around from the origional design. But now it plays in bypass, but when its activated all I get is a faint distortion with the amp up about half way
Any ideas where I might have went wrong?

do you know how to properly hook up a variable resistor? could be the problem , or a grounding issue.  most likely a solder joint bridge or issue if a faint sound is coming through from my experiences. reflow all solder joint and recheck for bridges. make sure you know how a variable trimpot works. recheck all grounds. make sure you measure all caps and resistors before installation to see if they are in working condition and tolerance. I believe the forum recommended to me a 10% tolerance and even possibly as high as 20% . I would be wary if you got them components from an ebay source; and most definitely would hook them up to a testing device before installation.

and please come back with all your transistor voltage measurements

[tacobender]

Thanks for the advice, I checked all resistors before installation. Caps I don't have a meter to check yet. But I looked at the layout I used and another bias layout, seems the first was wrong. The output on the wrong track, switched that got fuzz but still not 100%, I'm wondering what you would recommend changing the 8.2k resistor to when adding a bias pot? First layout had 470r but idk since it was wrong.

[LightSoundGeometry]

 I have read several places to leave the voltage divider alone and put a variable resistor on Q2

change Q1 base from 100K to 10K is also what EW suggested..I really dont know, I have put trimpots everywhere and cant get nothing ..its either me or bad trannies I keep buying ..I know the ones I got that crackle and hiss for over 20 bucks surly cant be right. but then again, I go on ebay and see every tom, dick and harry building pedals left and right and I fail more than not..probably just me. for example, I see freppes arcadiator everywhere, I mean everywhere, and I cant get one to work ...so who knows

[Electric Warrior]

I have read several places to leave the voltage divider alone and put a variable resistor on Q2

change Q1 base from 100K to 10K is also what EW suggested..

Because someone had changed it to 100k in the first place. 10k is the stock value for the OC75 version. Your voltages were much better with all stock values. It's a pretty good starting point.

Not sure what's up with your transistors. Smallbear wouldn't have sold you noisy ones I'm sure. Maybe you keep breaking them?


Q1's base resistor and Q2's collector resistor are the ones you have to mess with to adapt the circuit to higher or lower leakage. The rest is transistor selection. If you must have an external bias control, put it on Q2's collector.

[LightSoundGeometry]

I have read several places to leave the voltage divider alone and put a variable resistor on Q2

change Q1 base from 100K to 10K is also what EW suggested..

Because someone had changed it to 100k in the first place. 10k is the stock value for the OC75 version. Your voltages were much better with all stock values. It's a pretty good starting point.

Not sure what's up with your transistors. Smallbear wouldn't have sold you noisy ones I'm sure. Maybe you keep breaking them?


Q1's base resistor and Q2's collector resistor are the ones you have to mess with to adapt the circuit to higher or lower leakage. The rest is transistor selection. If you must have an external bias control, put it on Q2's collector.

oh I know, I am just frustrated is all. I probably did fry them out somehow.  its just the nature of the beast. I know its me . I will figure it all out.