Troubleshooting my Runoffgroove Omega build

Started by MetalUpYerEye, May 07, 2011, 03:38:38 PM

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MetalUpYerEye

Hey guys... I decided to build an Omega from runoffgroove to slam the front end of my new Blackstar HT5.  ;D

I had everything less the transistors so I built the whole thing and then ordered the trannys. Its kind of my way of making sure I actually put the parts I buy to good use. Anyway, I socketed the transistors when I did the build about a week ago so that when the parts came in I could plug them right in and go. No dice. I plugged the transistors in and i'm getting no sound out of it. When I turn the "master" (volume) up I can hear a slight amount of white noise increase and decrease with the turn of the knob. I have quadruple checked my transistor pinouts and as a last resort I took both transistors out and turned them around, trying all different possible orientations. I know the way I have them in there is correct though.

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

The only part substitution here is a 240pf cap in place of the 220pf. I used 2n5457 for the jfet (q1) and bs170 for the mosfet (q2). The drain of the 2n5457 is biased at 4.75v but I have tried rolling the trimpot up and down with no luck. It should work anywhere between 3 and 7 volts anyway. The layout used is a mirror image of the runoffgroove one. Its my first time using a perf layout from a website so I didn't realize I was looking at the wrong side of the board when I did it, but all the connections should still be right, even if the components are arranged in a mirrored configuration of the original layout. I went through and checked all my solder connections with my continuity function and everything seems to be in order. Here are the voltages for my transistors.

Q1 - 2n5457
D- 4.75v
S- 0.87v
G- 0v

Q2 - BS170
D- 8.3v
G- 5.84v
S- 4.02v

My battery was reading in at right around 8.35 volts when I took these measurements, so it was a bit low. A fresh 9v produced the same results although these measurements are still from the 8.35 battery. Any help would be really awesome!

Thanks guys!

B Tremblay

The voltage readings look good, so I'm guessing that there is a wiring error.  Can you provide a photo of the board?
B Tremblay
runoffgroove.com

MetalUpYerEye

Here's some pics of the board. Like I said the layout is a mirror image of the one at runoffgroove. When I started putting the board together I looked at the layout picture and imagined the components on the opposite side of the board, rather than being on the side facing me which is what I think its supposed to be.

http://i40.photobucket.com/albums/e215/metalupyereye/100_0983.jpg
http://i40.photobucket.com/albums/e215/metalupyereye/100_0984.jpg

Davelectro

Is lug 1 connected to ground for both potentiometers?

B Tremblay

I compared the photos with the perf layout and it seems to match.  Have you tried an audio probe?
B Tremblay
runoffgroove.com

MetalUpYerEye

#5
Quote from: Davelectro on May 07, 2011, 05:05:36 PM
Is lug 1 connected to ground for both potentiometers?

Lug 1 of the 'master' control (volume) is connected to ground. The range control has lugs 1 and 2 connected together and wired onto the 22k resistor, with lug 3 connected to ground. Should I change it so that lugs 2 and 3 are connected to the 22k and lug 1 is connected to ground?

I haven't tried an audio probe yet... After the beginners project, 2 Dr. Boogie's, Colorsound inductorless wah, EA tremolo, Tiny Trem, various 386 amps and a few other projects i've never been this far into troubleshooting that I need one... I guess its time to chop up a cable.  ::)

B Tremblay

Since the voltage readings look good and you have not found a wiring error, you need to determine why there is no output and the audio probe will help with that.
B Tremblay
runoffgroove.com

Davelectro

Well, actually lug 1 should be connected to ground. Lug 3 to both Lug 2 and 22K. But i don't think the problem is there.

MetalUpYerEye

I got it sorted out. I had a stereo jack on the output side which wasn't a big deal, but I happened to swap it for a mono jack and move one of my ground wires before I tried the audio probe. That must have fixed whatever bad connection I had because I traced the signal all the way through the circuit to the output jack with the audio probe and everything is working great now.

Thanks for all your help guys!

And man my HT5 was great before this thing but this pedal really makes it breathe fire!  :icon_twisted:

B Tremblay

Excellent, I'm glad you got it sorted out.
B Tremblay
runoffgroove.com