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Active Pickup circuit problem
Active Pickup circuit problem
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Old 14th January 2018, 04:47 PM   #11
GeorgK is offline GeorgK  Austria
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Join Date: Jan 2005
Location: Vienna
They forgot to draw the FET?!?
But I guess there is only one 10k source resistor?
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Old 5th February 2018, 05:11 AM   #12
argonrepublic is offline argonrepublic  Canada
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Join Date: Apr 2005
Location: Simcoe Ont
I wasn't able to located the source of noise yet. I did replace the 4558 opamps.
I have removed the preamp circuit from the guitar to isolated the pickups from the diagnosis. The noise is still present only when 9v is applied and volume control is at least 60 % clockwise. The noise sounds like a dark white noise with crackling and here is a picture on the scope.
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Old 2nd March 2018, 03:42 PM   #13
argonrepublic is offline argonrepublic  Canada
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Join Date: Apr 2005
Location: Simcoe Ont
Is there a common alternative to this Jfet K30A? I live in a relatively remote location with little access to electronic components. I am hoping I can dig something out of a drawer or rob one from spare boards. I really need my guitar today.
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Old 17th March 2018, 04:44 AM   #14
argonrepublic is offline argonrepublic  Canada
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Join Date: Apr 2005
Location: Simcoe Ont
Back to this again. I replaced a couple of components and ran it in series externally. It seemed to work until I connected it back inside the guitar. Here is another picture of the schematic without my drawing of the F30A that exists on the PCB but not in the schematics. In the original schematic, there is a capacitor in brackets between R1 and C1. It is absent from the PCB in my guitar. What would it be for and what would be a typical value? Thg
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