Tractor Beam not phasing

[jimilee]

I'm officially stumped, I have sound the internal volume works, voltages look good, can't hear phasing. Any help is appreciated.




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[danfrank]

Hi,
Voltages look good. Are you sure the FETs are in the proper way? It's like every FET has a different pinout.
On mine, it only phases when the internal trimmer (bias) is at one extreme end, I think CCW, IIRC. This setting has a lot to do with the cutoff voltages of the particular FETs used. I would have liked it better if this setting was more in the middle so it can be "dialed in".
I can't remember what the best cutoff voltage is for the FET set but if it's too low (< 1volt), the pedal won't work very well. I think ideal cutoff voltage is over 1.5 volts but under 3 volts. Considering the bias rail is 4.7 volts, that puts the cutoff of the FETs right around the middle of the bias rail.
Hope this helps

[jimilee]

Hey thanks are in right according to the pinouts and diagram. So no joy there.

Thank you!
-Jimilee


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[gordo]

Throw down a couple of pics, it'll be good to get some additional eyes on it.  Probably something you're looking right at but can't see.  Isn't that almost always the case :-)

Plus...you gotta get this one working.  I think the TB is my fave phaser.

[jimilee]

Throw down a couple of pics, it'll be good to get some additional eyes on it.  Probably something you're looking right at but can't see.  Isn't that almost always the case :-)

Plus...you gotta get this one working.  I think the TB is my fave phaser.

Cool man, I took some today of the top, the bottom is covered in pots.



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[jimilee]

Throw down a couple of pics, it'll be good to get some additional eyes on it.  Probably something you're looking right at but can't see.  Isn't that almost always the case :-)

Plus...you gotta get this one working.  I think the TB is my fave phaser.

Do you know the wet signal path? This schematic doesn't make sense to me.


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[gordo]

I think all your 47n caps are 4n7.

[jimilee]

I think all your 47n caps are 4n7.

Holy cow, that's a new one! Thanks for the eyes .


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[gordo]

Glad I could help. Downside is that desoldering VFE boards is a PITA.

[jimilee]

Glad I could help. Downside is that desoldering VFE boards is a PITA.

Yep, but they're so thick, the pads don't tend to come off. I can't believe I did that.


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