BYOC Octafuzz Not Working

[jhamnett]

Hi guys.  I know that BYOC has their own forum, but the tech support I'm getting there hasn't been able to help my problem, so I figured I'd posting here.

This is my first build after doing some mods.  I'm hoping to finish within the next week.  My octafuzz pedal has been having a huge volume drop and the intensity knob doesn't work while in use.  Bypass is fine.  I got 0V out of C7 (see board and schematic: http://www.buildyourownclone.com/board/viewtopic.php?t=6048).  By now, I know there's gotta be something grounding the circuit past C7 or a bad trace/solder joint.  Please take a look at my build's pictures: http://good-times.webshots.com/album/560306559QwnBUl.

Also, I broke one of the 1N314A diodes when undoing the octave lift mod.  I have replaced it with a 1N914.  What effect will this change have?

Any help is much appreciated.

[petemoore]

Also, I broke one of the 1N314A diodes when undoing the octave lift mod.  I have replaced it with a 1N914.  What effect will this change have?
  "Assymetric Octave" or 'less octave/still Fuzz [probably]the diodes should be sorta matched at least, I'd try 2x same type, low threshold diodes, I think 1n914's could be used to different sounding octave effect than GE's.
  Doesnt' sound like the 'problem' [you can get yer diode in there sooner or later]...
  I just debugged a couple BYOC's, a FF and a Tri-Boost, bascially when everything is as it should be it works...I missed a jumper, had a diode backwards, the diode backwards made input V supply like .79v, so I figured somethings 'clamping' yupp, the jumper was found by rooting through the PDF instructions to find where the jumper is mentioned...basically I found the problems by just 'DMM-ing' my way through on Mighty Mouse]...The Tri-Boost had signal getting to the Drain, but no boost, so I looked through and found the jumper mentioned, I'd used the 'thumbuzz' method from output toward input.
  I'd say voltages but I wouldn't make much of some of the transistor readings, wierd' stages may have 'non-linear' [wierd type bias points.
  Audio probing or 'thumbuzzing' through the circuit to find where signal is being lost is what I'd try on the octave.

[jhamnett]

I've always felt there should be a jumper in the circuit, but I just searched the PDF and there's no mention of it.  Like I said, something's happening after the 33uf cap with the transformer, diodes, C8, R12, and volume pot that is grounding when it's not supposed to.  It's frustrating, especially since I'm on the verge of finishing a Distortion+ in the time it's taken me to figure out this problem.  I'm going to rewire the pot and see where that takes me.

Also, will probably use 2 1N914s right now until I get my germanium diodes from PPP.

[jhamnett]

I'm now getting the same problem with a Distortion+ I just built.  When the effect is on, there is a HUGE volume drop.  It's very significant.  Is there a common newb mistake that leads to large volume drops?

With the Distortion+ I'm getting the volume drop with it off too, I'm going to check my wiring, especially the stompswitch.  At least the LED works...

[scotsman]

First thing I noticed is that your footswitch is missing the jumper from lug 9 to lug 4. 
2nd thing is more of a question - did the pedal work before you did the mod?  Or did you build it with the mod first?  Many wise men have stated that you should always build it "stock" first - get it working then add on your mods..

[jhamnett]

Scotsman -- excellent catch with the jumper on the footswitch.  That is something I knew before taking the photos and neglected to indicate, my bad.

Second, I build it initially with the mod.  I have since taken the mod out.  While doing that, I broke both of my germanium diodes, so they are now replaced temporarily with 1N914s.  Just did some rewiring and reflowing of the joints, haven't tested but I will tomorrow.

[ambulancevoice]

i dont think silicon diodes work in octave circuits
only germs do
from what ive seen heard
you probably get a replacement germ diode from BYOC

did you orientate the transformer correctly?
and also, i noticied you soldered the transistors
did you solder then as quickly as possible? or did you use a crocodile clip or a clip on heat sink?
cause transistors are damaged by excessive heat, so if you didnt use some sort of heat sink, or held the iron to long, it would have fried the trannies

[jhamnett]

I'm pretty sure the transformer is in the right way, I'll check again.

I hope I didn't burn out the transistors.  I was getting voltage readings out of them the last time I poked around with my DMM.

[MartyMart]

Silicon will work but the pair of 914's need to be matched to get a decent octave note.
Use you DMM to measure the forward voltage of some 914's to get a matched pair at say ... 0.65v for example

MM

[scotsman]

Why is C7 missing (33µf) in your pictures?

[jhamnett]

I pulled it because I thought it was busted, 0V out negative terminal.  I got a new one and tested again, same thing.  I've concluded there is a mistake after that capacitor, but I haven't been able to figure that out yet  .

[scotsman]

Build yourself and audio probe!  It wont take you long to find the problem with that.

[jhamnett]

Working on the audio probe, just need a 0.1uF cap and some electrical tape.

I took voltage readings last night for the transistors and they look OK:

Q1
C - 2.61
B - 2.54
E - 3.8

Q2
C - 8.23
B - 2.61
E - 2.12

Q3
C - 4.46
B - 2.11
E - 1.48

Still getting 0V coming out the negative lead of C7 and through the rest of the circuit.  Something between that and the output jack is not well connected.  I'm resoldering and reflowing, hopefully I'll find it (btw, not the diodes -- just put in two 1N34As today and I know they're in there good).

[jhamnett]

I took out the audio transformer and then got voltage out of C7.  I connected a wire with alligator clips to the transformer input.  Got fluctuating voltage out of one side, nothing out the primary side.  Bad transformer or bad PCB trace?

[jhamnett]

BUMP

[jhamnett]

Annnndddd... bump

[kahel]

You may want to do this bumping back at the BYOC forum... we're there. But yes, a bad transformer looks like the most likely culprit now. Replace it, report back, you know where. ;-)

K

[jhamnett]

K - Just trying to use all my resources .  I'll replace and report afterwards -- I know where.