ROG 18 pedal, Working Now, Need help biasing

Started by debutvm, June 19, 2006, 05:47:16 PM

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debutvm

This is my first pedal after the begginer. I have it completed and working now. I now have the truebypass up and running and I can get sound out of the pedal. First off the I can only get the pedal to do anything when I turn the trimpots and find sweet spots in them. I can only move the trimpots in very small incremints or I will have no sound at all.  Is this normal? I need to bias the transitor but dont know how to. I have been putting the common lead of my multimeter on the negative batt side and probing the transitor pins with my red lead. No matter which position I turn the trim pots at I get 9.5 v on all of my D pins..This being I believe that I am doing something wrong and need someones help. I have been doing searches on the board but havnt been able to find something in retard terms that I can understand. Also the pedal sounds very much like a fuzz, with little treble which I dont believe to be correct. Here is the link to the project.

http://www.runoffgroove.com/eighteen.html

Anyones advice would be great becomes im definately stuck. Thanks


markm

Alot of the time I just adjust the trim pots so that I get signal going through the circuit and then,
fine tune them by "ear" to what sounds the best to me without gating.
It's simple but, it works.

BGillis

I had a similar problem with trim pots... Mine are NTE 100k and they have three pins. If you check the resistance with your DIMM you might find as I did that you need to check it from either one of the end pins to the middle pin to see a change. I then changed my wiring so the middle pin of the trim pot went to the Drain on the transistor and was able to adjust the voltage from there. I don't know much about this stuff but it worked for me.

Hope this helps,
Brian

debutvm

I think i got it. Thanks guys. All seems well with the pedal. I do believe im going to need to add some treble though, but right now im playing through a behringer 210 so that would defintely explain the nasal bass and no treble..I sold all of my other amps to get a Carvin V3 wich is now on backorder. I believe i will hold off the mods until i get that puppy to work with. I will post pics/sound clips when i recieve my new head and play with the pedal a bit..