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I’ve had this PCB for a while. Recently I’ve been interested in Leslie sounds from pedals like UniVibe. So I put this one together. The only variation from the parts list was the use of a 200K trimpot instead of the specified 250K pot and I used J201 transistors. They were installed opposite to the graphic on the PCB so the pinout is correct.
I have tone but no vibe. I have carefully adjusted the trimpot but there is no effect.
I have included a couple of pictures of my build. I have re-flowed ‘most’ of the solder joints.
I’m stuck. Any suggestions??
Regards,
Alex
Your fets need to be a matched quad set, if they are
It’s a 500K trimmer code 504 you’ve got but it should still work use the trimmer to set the fet gate pins to just over 2v that’s the phasing sweet spot for 5952s because yours are J201s start there and adjust the trimmer in very tiny increments
J201s are not ideal for phasers they will work if matched but will probably give a much more subtle effect
Thanks very much. I’ll swap out the j201s and the trimmer and will let you know how I made out.
Alex
You don’t need to swap the trimmer higher than required resistance is fine it may just take a little longer setting the gate voltage
You only need to set gate voltage on one fet they’re all connected so if you set 1 you set them all
The most crucial thing is the fets are a matched quad set they’re being used as variable resistors
I’d try it with the J201s first you never know your luck they might just work if not you should be able to get a matched set of 2N5457s still
Where are you located
Hi Billy,
I’m SO sorry for not responding! Life got in the way there for a while! I do really appreciate the help and suggestions.
Since I last posted, I have replaced the J201s with matched 5457s and the trim pot to a 300K trimmer.
The result is the same. Unchanged sound engaged or bypassed. By the way I did the 2/4 stage mod as well.
To answer your last question, I’m located in Ontario Canada.
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