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Re: Arion SCH-1 chorus

11/17/2002 2:46 PM
Boy Howdy Re: Arion SCH-1 chorus
The trimpot acts more like a switch than a pot. If it's set at 12:00 now, when I turn it to 10:00 the effect goes away. I have to return it to 12:00 to get the effect back. I was able to get it to distort by setting the trimmer to a certain position. In short, it seems to mimic the (defective) behavior that the unit is exhibiting on its own.  
I didn't have enough time with it yesterday, but the last time I played through it I was not able to get it to cease functioning. I could not say for certain whether or not the sound quality diminished at all. It usually takes, I'm guessing, around ten minutes for the sound quality to start to diminish.  
In the process of installing the new cap, the circuit board trace lifted from the board. What to do? ...Other than panic. ...I'm pretty good at panic-ing.
11/18/2002 2:33 AM
Boy Howdy

Well, the darn thing just seems determined to work now. I don't know what's up with it. It's been on continuously, pretty much all day. I've been learning a bunch of songs, so I've played through it about four hours today and have left it running when I wasn't playing through it.  
I'm at a loss to 'splain it.
11/18/2002 5:15 AM
Mark Hammer
What explains it is that the trimpot adjusts input bias voltage. Your description of how it cuts out the effect and brings it in nails that trimpot as having that function.  
My own best guess is that you had it originally set to just the cusp of passing signal, and that perhaps it would occasionally drift to the wrong side (you DO have to step on the pedal once in a while, right?).  
This confirms for me what I've claimed on these very pages many times over: one of the biggest source of headaches and failures with BBD-based devices is the input bias voltage. Though trimpots provide precision in setting it, they also provide failure when the trimpot drifts over the years.
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