Author Topic: Boomerang Wah Questions  (Read 2882 times)

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stumper1

Boomerang Wah Questions
« on: September 22, 2007, 06:30:19 PM »
I finally got back to my Boomerang Wah that I never got working.  I originally did my own layout using Paul's schematic.  I had issues I couldn't figure out so....etched another board using Paul's layout (Thanks!).  While removing parts from my old board and checking/testing them before putting them in the new board - I discovered that I had a bad (though brand new) inductor.  Replaced the inductor and it fired right up :).  Sounds great  - but I have 1 issue.

In the toe down position - the pot sounds noisy/scratchy.  It's only in the very last bit of rotation (about 2 1/2 teeth worth if that makes any sense).  I'm using a *ulltone 100k pot.  Tried a 200k wah pot and a 25kB alpha.  All three had the same issue.  Replaced all 3 electos on the board - no change.

I can adjust the pot to the point where it doesn't go that far - but I don't think I should have to.

Any ideas?

Thanks 8)
Deric®

Arfman

Re: Boomerang Wah Questions
« Reply #1 on: September 22, 2007, 06:34:49 PM »
I finally got back to my Boomerang Wah that I never got working.  I originally did my own layout using Paul's schematic.  I had issues I couldn't figure out so....etched another board using Paul's layout (Thanks!).  While removing parts from my old board and checking/testing them before putting them in the new board - I discovered that I had a bad (though brand new) inductor.  Replaced the inductor and it fired right up :).  Sounds great  - but I have 1 issue.

In the toe down position - the pot sounds noisy/scratchy.  It's only in the very last bit of rotation (about 2 1/2 teeth worth if that makes any sense).  I'm using a *ulltone 100k pot.  Tried a 200k wah pot and a 25kB alpha.  All three had the same issue.  Replaced all 3 electos on the board - no change.

I can adjust the pot to the point where it doesn't go that far - but I don't think I should have to.

Any ideas?

Thanks 8)

I just modified a guys wah pedal. I got the info from Geo Technology of the Wah pedal, specifically the LDR mod mentioned that was by Craig Anderton. I didn't get it working with a LDR, it worked but there was a perceptible delay from hi to low as the LDR went dark, but I ended up going to RadioShack and getting an Infrared LED/Phototransistor pair (same package)...I had to rebias the LED part of it but it worked great! No scratch whatsoever...

One issue though is that LED draws 100ma so it's a battery killer...you'll want to use a power supply...

stumper1

Re: Boomerang Wah Questions
« Reply #2 on: September 22, 2007, 09:04:27 PM »
Arfman,

Thanks for the tip - I'll look into it.  The thing that has me wondering is that I tried 3 different pots - all brand new - and they do the same thing.

Deric®

Paul Marossy

Re: Boomerang Wah Questions
« Reply #3 on: September 23, 2007, 10:06:42 AM »
Quote
The thing that has me wondering is that I tried 3 different pots - all brand new - and they do the same thing.

Yeah, I am wondering about that, too.  :icon_confused:

B Tremblay

Re: Boomerang Wah Questions
« Reply #4 on: September 23, 2007, 11:07:18 AM »
Which schematic did you use?  IIRC, Paul had two at his site.  I know that I started with one and it wasn't quite to my liking, so I modified it and came up with this:

http://www.diystompboxes.com/smfforum/index.php?topic=52412.msg396085#msg396085
B Tremblay
runoffgroove.com

stumper1

Re: Boomerang Wah Questions
« Reply #5 on: September 23, 2007, 12:35:35 PM »
Thanks for the replies.

I used the BG-1 schematic that is currently on Paul's web-site.  I used the values on the schematic - not the values on the PCB layout on the same page (68k input resisitor and 820k feedback resisitor on Q2).

I want to figure out the pot issue before I start tweaking other values.  I'm going to "listen" to the pots I used in another circuit as well as double check my wiring.

So far - it sound great. ;)
Deric®

stumper1

Re: Boomerang Wah Questions
« Reply #6 on: September 23, 2007, 03:21:02 PM »
Well.....no luck.  I tested the pots - all three of them - and they were fine.  I reversed the pot wiring out of curiosity and the "scratchy" sound moved to the other end (heel down).
 ???

Swapped out Q2 (BC109) for a new one - no change.  Double checked all my wiring.

Played with it for a while - sounds VERY good - and adjusted the pot to where I like it best.  When it's adjusted where I like it, it doesn't get to the "scratchy" part.
Deric®

jaytee

Re: Boomerang Wah Questions
« Reply #7 on: September 23, 2007, 05:38:57 PM »
DC on the pot/leaky cap?

skiraly017

Re: Boomerang Wah Questions
« Reply #8 on: September 23, 2007, 05:46:25 PM »
What kind of wah casing are you using?

I bought an original Boomerang 2 and the pot was no good. I swapped it out but when I was in the toe-down position about ready to turn it off, I get a loud scratch/pop. I thought the pot was bad so I replaced it with the same results. After the third replaced pot I realized that the tab/bracket that the pot mounted to was not cast evenly and when I tightened down the nut for the pot, it work torque the pot and cause the wiper to jump in that section of the travel.

If you take the pot out of the bracket and rotate it manually, do you still get the same problem?
"Why do things that happen to stupid people keep happening to me?" - Homer Simpson

stumper1

Re: Boomerang Wah Questions
« Reply #9 on: September 23, 2007, 06:27:26 PM »
Checked for DC on the pot.  Swapped the caps just in case and same thing.

It "scratches" whether the pot is mounted or not.  The 2 other pots I tried were never mounted in the casing.  Also, it moves to the other end of the rotation when I reverse the wires on the pot. ???
Deric®

Shepherd

Re: Boomerang Wah Questions
« Reply #10 on: September 23, 2007, 06:56:43 PM »
I had similar experiences with the boomerang.  I'm aware of the crackle/scratch sound you're referring to.  A practice amp can disguise it sometimes, but it's still there.  I tried a bunch of pots and they're fine with slow sweeping, but the fast sweep results in scratchiness. 

stobiepole

Re: Boomerang Wah Questions
« Reply #11 on: September 23, 2007, 07:27:29 PM »
I'm getting the same thing myself, but with a Bow-Wow Yoy-yoy clone. Scratchy noise at one end of the pot...There was a missing cap on the layout and some other discrepancies I haven't played with, but no solution yet.

I've also built a Boomerang, but it's scratch-free. I used a 25k pot.

I was just about to suggest swapping the caps, but that's been mentioned already. Tried tants (less leaky)? Film caps?

I'm going to try different inductors next (the bow wow uses two, unfortunately).

Chris

Paul Marossy

Re: Boomerang Wah Questions
« Reply #12 on: September 23, 2007, 08:11:16 PM »
On my original BG-2, I sometimes get that scratchy sound at toe down right before switching off the wah to volume pedal mode. After hearing other people's comments in this thread, I'm beginning to think that maybe it's just a quirk with this particular circuit.  :icon_confused:

I still love my Boomerangs, they give a nice fat tone when using the neck pickup on my guitars. I use the neck pickup 98% of the time, and it gets a nice mid-range growl that way.  :o
« Last Edit: September 23, 2007, 08:13:36 PM by Paul Marossy »

stumper1

Re: Boomerang Wah Questions
« Reply #13 on: September 23, 2007, 08:17:31 PM »
Hmmm....me too.  A freind is giving me his real Boomerang tommorow - no idea if it's a 1 or 2.  He said his dad (who bought it new) quit using it because the pot was scratchy. :o 

Paul, what size caps are you using?  I had 1u, 1u and 4.7u but changed them all to 10u when I was looking for the problem.  Is it worth switching back?
Deric®

Paul Marossy

Re: Boomerang Wah Questions
« Reply #14 on: September 23, 2007, 09:09:10 PM »
I used all the stock values in my Boomerang clone.

stumper1

Re: Boomerang Wah Questions
« Reply #15 on: September 24, 2007, 05:12:18 PM »
So my buddy brought me his BG-2.  Opened it up and found the pot had been replaced.  It has a 50k Alpha w/a 50k resistor across it.  Turns out, shortly after his dad bought it he had the pot replaced because it was "scratchy" in the toe down position.  Never plugged it in for about a year after he got it "fixed".  When he finally did - it was "scratchy" in the same spot so he never used it agian. Hmmmm.

Other than the pot, the pedal is near mint.  Still has the funky bag it came in. 8)

Sounds great.  Pretty much dead on with my clone - even the "scratch". 

Big THANKS to Paul Marossy for the layout, schematic and inspiration.  And thanks to everyone else who chimed in with suggestions! :)
Deric®

Paul Marossy

Re: Boomerang Wah Questions
« Reply #16 on: September 24, 2007, 05:31:26 PM »
Cool, glad you are happy with it.  :icon_cool: