Maestro Wah not working

Started by fixxe, May 12, 2013, 06:47:40 PM

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fixxe

Hey, I built a maestro boomerang clone and unfortunately it is not working. The bypass is working.
But I'm not sure where the mistake is. So I drew my built and maybe someone can tell my if there's something wrong.

The filter cap and the transistor orientation I'm not too sure about either...  :icon_confused:  Do the little tab of the transistor and its socket need to be aligned?
Also there are following mods: a resistor across CW and CCW to bring the pot to about 25K and a trimmer at the bottom right set to 47K.

I'd be a very happy man if someone could help me!  :)

Here's a link to the schematic:
http://www.montagar.com/~patj/mboomer.gif





Link to drawing:
http://s14.directupload.net/images/130513/xwjc7uqv.jpg




fixxe

I must add that I switched the connections of CW and SL to the board once, which didnt help my cause either. The way they are connected now, are probably very wrong.   ;D

pinkjimiphoton

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

filter cap + goes to power jack +... as shown, it's wrong, it should be in parallel with the +/- of the jack, not in series with the + voltage as shown.

simply put + and - of the cap to the + and - of the power jack... remember, center of the power jack is most likely NEGATIVE, not positive.

transistors aren't marked on this drawing so it's hard to tell what's what. generally the tab goes to the emitter, but this isn't always true.

we need voltages... click the link, and squash that bug!!

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joegagan

i assume you have a vero cut under the 68k input R that isn't shown. ( same Q applies to the 1.0 and .01 caps) you seem to be showing a 47k to ground off the E of Q2 that should be 8.2k.

your 1.0/ 6.0 cap orientation looks correct.

don't understand your socket Q. do your homework and assure your transistor pinout is correct.

that old schematic shows a 4.7k off of B of Q1 to inductor, in reality the real BG1 maestros have 1.5k like the BG2s had. 4.7k will work, but 1.5k sounds more like a real BG1.

when simming boomerangs in spice, the 33k R across the outer lugs of a 100k pot cause a weird curve in the freq response. this has also been my experience ( audible) in many boomers sent to me that had that trick installed. this is 33k to ground all times, the bias of the transistors is affected.
use a 50k pot for best results. ( vintage boomer pots typically read 15- 20% higher than 25k , so when an actual 25k pot is used a loss of treble results.)

hope you find your problem, keep us posted.
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fixxe



YES!!!!!!!!  :D

Thank you guys, it's working now!
Though I'm ashamed to say why, haha. For one, I connected my power to the wrong positiv (the other pin) of the power jack. And then I forgot to cut the traces under the parts that are parallel to the vero-strips   :-X   (what a mistake...)
I will try the suggested parts as soon as I'm ordering new parts and will definitely try that out.

One more question: Do I need to connect the negativ of the power jack with the ground of the board like here?:
http://www.beavisaudio.com/techpages/PedalPower/

Oh and my question regarding the tranistor sockets: My sockets have a little tab like the transistors. But when I install them the right way, those tabs don't line up. But I guess that doesn't matter, does it?

Thanks again everyone!  :)

Gus

Joe where did that 33K idea come from?