DS1 new problem...squeals(hi-pitched whistle)

[sonofmickel]

The Distortion knob issue was fixed by poor factory solder. I tested the pedal into the clean side of a JCM800 clone, seemed to work fine.
Then I plugged the DS1 into the Hi gain input on the JCM800, the DS1 makes the amp squeal at any volume(not at zero). I tried an OCD and other pedals that worked fine into the hi input. The squeal followed the DS1 to a Quilter 101 solid state amp head(that ruled out the JCM800). On the Quilter the pedal squealed only on the "Lead" channel(adds a gain stage), the OCD worked fine.

9v Battery or isolated power supply results were the same.

So the SD1 is squealing into medium/hi gain amp inputs.

[GibsonGM]

Hi Mickel, Welcome!  Got some pics of your build?  Would like to see the wiring going from your jacks to stomp switch and so on.  Often, these wires can act like little antennae that pick up signal from inside the circuit, and send it back to the input (positive feedback), which leads to oscillation (squealing).     Sometimes it's unavoidable at very high gain settings, but there are often things that can be done to minimize it....

[sonofmickel]

Thanks for the reply GibsonGM
The pedal is an actual stock Boss Sd1, it was just given to me by a neighbor(he bought it new a few years ago and it didn't work originally, so he didn't use it...or return it?).
I'll take it apart and get some pics.

[antonis]

I should check C7 cap (100 - 250 pF, depended on particular DS-1 edittion..)
The one connected between (Dist pot wiper + 100k resistor) & IC out..

[ElectricDruid]

+1. Antonis' suggestion is good.

Another possibility might be a bad ground connection somewhere. If something isn't grounded when it should be, you could get noise going in that shouldn't be there.

[sonofmickel]

Pedal is fixed.

Bad Gain pot from new(middle lug was intermittent).