hey there i am somewhat new to building guitar effects. So far I have built a simple fuzz face and a jfet preamp.
I am trying to build the rocket but i cant get a signal. Well actually if a turn the amp and pre all the way up ican get a low level noisy signal but this completely unintentional. I think ia may have a problem eith my transistors. They are gneralpurpose transistors from radio shack with an hfe listed as 200 the voltages on each lead are as follows
q1 C-8.5 B-4.35 E-1.24
q2 C-7.3 B-.18 E- .01
d3 C-7.6 B-7.1 E-.2
I dont know what to make of it and looking at the faq on geofex was helpful but i cannot determine what to do next. I have triple checked all my component values and resoldered the entire board All i can say at this point is help
I believe Q's 2 and 3 should be biased like a FF, Q3 should be about at 1/2 supply voltage [~4.5v of 9v] 4.5v.
Try adjusting the trimpots and see if that helps.
I'm sure you checked Transistor pinouts...I've missed them up before then found out I didn't find the problem the first, nor 4th time.
Welcome jeremy. :D
Try measuring the collector of Q3 while you adjust the bias pot. You want to end up with something like 1/2 of Vcc on the collector there; in this case, roughly 4.5V. That should drastically change the values for Q2 also.
If you still don't have sound after adjusting the bias, repost the voltages you see and I'm sure a fix can be found.
Best of luck!
-Peter
alas alack i tried mr snowbergs suggestion but to no avail. Turning the bias pot only vairies the collector voltage of q3 7.72 and 7.46 volts. By the way you guys are quick.
Hi Jeremy, Being a Hewb to pedal building myself, here's a few mistake's I have made, maybe they will help you, maybe they won't, I had some transistor's reading the same way on one of my build's and what I found was the Transistor's that I bought as a replacement for the build had a different pinout on the leg's, make sure you know which leg your hooking to each part of the circuit, I had to swap out the base and the emitter leg's, then I was able to bias the tranny's, I've also had a few cold solder joint's also that caused funny reading's, take your time and walk your self back through the circuit, that's how I find some of my mistakes,
Hope you get it working,
JD
yearggghhhhhhhh
i cant believ it i tried reversing the pinout and it worked. The pinout diagram on the back of the freaking box was wrong it had the pins backwards. This is infuriating. Well thanks to all those who offered help. It was much appreciated
Wrong pinout. A classic mistake we all learn from :wink: