ROG Peppermill noise problem. help needed

[jamiefbolton]

Hey guys, thanks for stopping by. Here is the deal. I've built two ROG Peppermill into one enclosure and each independent of the other. But, I'm having the same problem in the same spot on both. I broke out the audio probe and everything is clean up until the Drain of the BS170 (yeah I know, that only three components into the circuit  ). Gate and Source are good too. I'm guessing that since each circuit is having the same problem in the same spot, the power could be the source of the noise. I'm using a walmart 9v adapter. Could this be the problem? I've used them successfully in the past.

I've built stuff in the past, so I'm not a complete idiot  but you guys are probably better than me, so what is a good direction to look? Power?

http://runoffgroove.com/peppermill.html

[jamiefbolton]

certainly its not two bad BS170s?

[frequencycentral]

Try running it from a 9v battery. If the problem goes away then the 9v adapter is the issue. Also would be a good idea to add a 100uF (or similar) elecro cap from +9v to ground at the DC socket or close to.

[Kearns892]

Not to sound condescending, but have you double checked the BS170 pinout? What layout are you using?

[jamiefbolton]

I double checked to pinout and it seems to be right. I'm using the layout from ROG that is supplied on the website. I'll add in a 100+ cap and see what that does. I don't have a battery hookup in the pedal, but maybe I can add one to see if it helps.

Thanks guys. I'll report back when I get a chance to try your suggestions.


jamie

[jamiefbolton]

i think it was the power supply. i hooked up a battery and things are much much better. but now i have a second question. how can i amp up the gain just a bit? i want the second channel just a bit more driven than it currently is.

thanks

[frequencycentral]

I think adding a 10uF cap to ground from the BS170's source would increase the gain. Or you could try replacing the BS170's drain resistor with a FET like this: http://www.diystompboxes.com/smfforum/index.php?topic=83692.0

[jamiefbolton]

i'll try the 10+ first and see what happens. thanks.

[B Tremblay]

You could reduce the source resistor of Q1.  470 or 510 to start.

[jamiefbolton]

ok on the second channel i'm not getting the proper voltages to the BS170. i'm still over 8v on the drain. it should be 5.6v. and i'm getting no output on channel 2. channel 1 is fine.

i've used the audio probe and i get signal up until the drain of BS170. i've looked and compared the two layouts and everything seems to be the same. and i've replaced the BS170 with no luck.

is there something i could be overlooking?

[jamiefbolton]

yeah i've been working on it. still no change. should i raise the value of the 4.7k resistor fro 9v to BS170 drain?

[jamiefbolton]

still no luck. i added a 100k to the 4.7k from 9v to drain: no change
i even changed the 1M in connection with the 4.7k. no change. cleaned and resoldered the BS170 and the trim pot. no change. i'm at a loss now.

[jamiefbolton]

the trim pot works fine. i've got 4.5 at the J201. but i get nothing but 8.6 at the BS170.

i really don't know why. this build is the same as the other. why or why? 

[Kearns892]

Wait, is the peppermill functional now and you are just trying to tweak it or is there still an issue?

[jamiefbolton]

its two pedals in one box. one build works fine, the other is identical (well, supposed to be) and is not working.