Dr Boogey squeal

[budjb]

Guilty on 2 of those counts.

How would you suggest isolating the input jack from the enclosure?

My pot ordering is (from left to right): Gain, Presence, Treble, Mid, Bass, Volume.

[frokost]

See the schematic. Both the presence and treble pots are at the end of the circuit. Putting them so close to the gain pot may feed the signal back in the circuit and cause oscillation. I suggest you lay them out as drawn in the layout, i.e. gain, bass, mids, treble, presence and volume and see if that helps.

[budjb]

I'm sorry, I had the order switched in my head and swapped Gain and Volume.  It is actually laid out the same as the layout on GM's site:
http://gaussmarkov.net/layouts/drboo/drboo-perf.png

[frokost]

If you power it with a battery and with no other pedals, what happens?

And I'll have to throw in this extremely stupid question, since this was a hard one: Are you sure it's not just feedback from the amp? 

Can you describe the squeal? High pitch? Low pitch? Sounds like Bruce Lee?

[budjb]

I haven't tried it with just a battery.  I've been using the Boss power adapter.  I could buy some 9 volts and give it a shot.

And yeah, I'm sure it's not the amp   Playing through a boss metal zone, I can turn it way up without any of this happening.  I do, of course, get some nice feedback from the strings of the guitar, but this is stopped by holding the strings so they can't vibrate.  With this Dr Boogey turned up, it's not the guitar and it's quite ear piercing   It's high pitched.

[budjb]

These images are straight from a 10MP camera and aren't resized.

Keep in mind this is my first build, so don't laugh 

http://www.budjb.com/boogey/IMG_3246.JPG
http://www.budjb.com/boogey/IMG_3247.JPG
http://www.budjb.com/boogey/IMG_3248.JPG
http://www.budjb.com/boogey/IMG_3249.JPG
http://www.budjb.com/boogey/IMG_3250.JPG
http://www.budjb.com/boogey/IMG_3251.JPG
http://www.budjb.com/boogey/IMG_3252.JPG
http://www.budjb.com/boogey/IMG_3253.JPG
http://www.budjb.com/boogey/IMG_3255.JPG

[frokost]

Doesn't look too bad.. However, I see several possible cold solder joints, about 10, in fact. Try to remelt every joint, make sure they're good. Also, clean the flux - that stuff sometimes leads to strange problems.

[budjb]

I removed the entire thing from the box and reheated any joints that looked like they needed it.  Still no go.  I have yet to scrub the board to get the flux residue off.  Is acetone recommended for this?

I'm just about resigned to calling the build a failure.  It sounds just ok starving Q1 and Q2, but it doesn't have the bite I was after.

[bside2234]

Check between the input pad and R18. Is there a solder bridge? The soldering on C6's leg towards the edge of the board looks bad.
Check between C13 and R15 for a solder bridge. Also the solder on the other leg of R15 doesn't look good.
Do you have a wire going from Lug 1 of the volume pot to ground? If you were following GM's wiring there isn't a wire where he grounds the volume pot.

[John Lyons]

Did you try replacing the Fets, swapping out for others?
I know you said you tried an MPF102 at the first fet
but sometimes you get a hot one and it will be noisy.

Try some others if you have them.

Several of the solder Joints looked compromised
as others have said. You fixed those so that's
probably not the issue now. Looks pretty good for a first
build better than mine were!

[budjb]

I will recheck for solder bridges tonight.

The ground from lug 1 of the volume pot I sent straight to the ground lug of the output jack.  The board was real tight around the space the wire would have gone.  I figured this would be ok - could this be a possible cause?

The only extra fet I have is the MPF102.  I could swap out each one individually and see what happens.  I've done that already with Q1, Q2, and Q5 to no avail.

Also going to make another pass looking for bad solder joints tonight.  I really need a magnifying glass for this stuff.  It's so much easier to see the problems with the macro shot from the camera than with the naked eye.

I've also had some pretty bad luck with my shielded cable.  Half of them broke off at the board.  Guess I wasn't careful enough when I stripped the center conductor.

[budjb]

I moved that ground to the pad on the board as per the schematic, and it actually made a difference.  I also went through and made another pass at checking for any solder points needing reheating, and redid a few of my cables.  Also scrubbed the board with rubbing alcohol and really cleaned it up.  Using the MPF102 in Q1, I was able to get some very nice distortion out of the pedal without the squeal.  It isn't gone completely - I can turn it up way past what I'll ever have it at and it squeals like a pig, but it's now usable.

I tried moving around while playing to see what effect that had on the situation.  Turns out that this happens when I stand closer to the amp.  Moving away helps.  I guess you can consider this feedback but I've never had this happen with my metal zone.

[John Lyons]

Ok! Getting better, that's what I like to hear!
I would recommend getting some more fets
and trying to swap out for different ones.

Get a magnifying glass and go over those
connections again and be sure to add a little
fresh solder. The joints need more flux when you
reheat them or they get "dry" and fail sooner.
"Wetting" them with some fresh solder will
fix this up. Just a little is fine.

John

[budjb]

So my amp may have been part of the problem.  I adjusted all my EQ settings to 12 oclock on the amp, and this pedal really comes to life.  It was orgasmic, to say the least.  And now, the EQ on the pedal itself really shines.

Lesson learned, and a successful first build