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Tractor Beam not phasing

Started by jimilee, May 16, 2020, 02:03:55 AM

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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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Pedal building is like the opposite of sex.  All the fun stuff happens before you get in the box.

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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Pedal building is like the opposite of sex.  All the fun stuff happens before you get in the box.

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.
Gordy Power
How loud is too loud?  What?

jimilee

Quote from: gordo on May 16, 2020, 05:20:12 PM
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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Pedal building is like the opposite of sex.  All the fun stuff happens before you get in the box.

jimilee

Quote from: gordo on May 16, 2020, 05:20:12 PM
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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Pedal building is like the opposite of sex.  All the fun stuff happens before you get in the box.

gordo

I think all your 47n caps are 4n7.
Gordy Power
How loud is too loud?  What?

jimilee

Quote from: gordo on May 16, 2020, 11:12:56 PM
I think all your 47n caps are 4n7.
Holy cow, that's a new one! Thanks for the eyes .


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Pedal building is like the opposite of sex.  All the fun stuff happens before you get in the box.

gordo

Glad I could help. Downside is that desoldering VFE boards is a PITA.
Gordy Power
How loud is too loud?  What?

jimilee

Quote from: gordo on May 16, 2020, 11:27:59 PM
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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Pedal building is like the opposite of sex.  All the fun stuff happens before you get in the box.