I think I'm a bit unsure on if you meant cable or jack socket in the test you mentioned, did you mean on the tip of jack cable when its plugged in the jack socket? is there any link you can show me? But I did try alot of different things based around that but didn't get any beeping. I'll probably look more into that tomorrow, as its getting late here.
Is this the sort of test I should do? - https://www.youtube.com/watch?v=nxhSotfKZEE
I looked up the receipt for the jacks they were on ebay, it was labelled switchcraft stereo but theres no link available for it.
I did a little test on the jack lugs which might be useful info, and heres a closer look at them - https://www.dropbox.com/s/c7fhdr3ubiy988g/20170111_214621.jpg?dl=0https://www.dropbox.com/s/itsflm0nppo3a50/20170111_214705.jpg?dl=0
I shifted both the wires (red on the right, black in the middle - according to picture 1) I shifted them both left. So now the red would be in the middle and the black on the left.
I got signal, but oscillation still. I unconnected the input jack and the oscillation stopped again like before. I also tried black wire on the left lug and red on the right, but got nothing coming through.
This is all with the original silicon FF circuit like schematic on the first post.
Edit: I watched the youtube link I posted and did the same sort of test. Turns out one of the jacks beeped when I touched the ground lug and a lug which wasn't ground, it wasn't the input lug, but the one that isn't connected in the pics. (Sorry I'm confused with what lugs are labelled what at the minute haha)
The other jack didn't do that, so I'm going to assume that they're not meant to be connected?
I have another jack spare so I'll get testing it tomorrow