Bias JFET?

robfallon

New member
Built a Son of Ben 2 years ago. Biased it by ear. The thing sounds great! It's been on and off my board... of late back on. Now curiousity has the best of me and I'm wondering if this great pedal will sound even better if I actually bias the thing to spec. Problem is I don't really know what Im doing. Ive seen a few threads clearly laying it out. I just can't get my DMM to do anything. Ive run it through basic troubleshooting and It seems to be in working order.

DMM is set to 2K. When I turn it on, screen goes immediately to 1.

I remove Q1 from socket.
Probes on D100-K and bottom of R2. Adjust the pot, Nothing happens Screen stays at 1.

Do I have a short somewhere? It's completely possible as it was my first ever build. If there is a short, would it still sound good? Guess that is subjective. Is my DMM a POS?

Thanks in advance. IMG_0222.jpg IMG_0220.jpg
 
Switch your DMM to 20K. It's indicating that it is overranging on the 2K scale. Adjust TRIM1 so you get a 12K reading. Done.

We're measuring TRIM1 & R5 in series. R5 = 10K. We want TRIM1= 2K. 10K + 2K = 12K.
That makes sense... My DMM must be a POS. 2K, 20K, 200K nothing changes but the decimal place... no reading. If I go to 2M I get a reading.. 1.235 nothing changes when I adjust the TRIM.
 
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