Below I have attached pictures of the front and back of my stripboard, I have extensively checked already for solder bridges and ensured that I have cut the copper strips in the right places.
Also have used my multimeter to check that the power I am getting in is ~12v (it actually is reading like 13.5 but I’d assume that’s not much of an issue, especially as Eddy states that it can be run off a 15v power supply anyway.)
So yes, it would be amazing if you have any ideas or can spot where I have gone wrong. I’m still shocked that everyone is so nice and generous with their knowledge.
First, not all transistors produce noise. It’s being used in a mode it’s not designed for and it’s not guaranteed it’ll do the same thing as the next transistor (especially ones from different batches). I would not solder up a noise circuit without first building enough of it on a solderless breadboard to verify the transistor works.
I have breadboarded that circuit and none of the BC547 I had worked, but several 2N3904 did.
If you don’t have a scope, you can try an audio probe to trace the signal. At the transistor emitter (or maybe better at the other side of C1) I’d expect the noise to be faint but audible. At the TL074 pin 1 it should be clear and of course at pin 7. If it’s absent in any of those places that’ll narrow down where the problem is. Of course if you have a scope it’ll be easier to check with that.
Incredible, thanks all. Will look at building this probe and tracing around the stripboard a bit.
Most likely will have to sub in a 2N3904 by the sounds of it. I imagine that I could essentially perform a straight swap, still cutting off the Collector leg and connecting the Base and Emitter legs in the same places?
Again, thank you so much for all your help and advice!!
A BC547 might still work, maybe just not that BC547. And any given 2N3904 might not work, too. As I said, I’d breadboard the circuit first or at least the top section of it to see if it works.
A straight swap, but bear in mind the BC547 and 2N3904 have different pinouts.
Right right, I’m following you now. I’m thinking of soldering some wires onto this board then and breadboarding to find a transistor that will make noise I guess!
If you have a guitar of some sort, you could also use it as a sound source, to test if the opamp circuit works. The first stage of this circuit is mostly a very large amplifier so you should be able to hear something.
I’d done all the steps, trying different transistors, double checking the power in onto the stripboard, plugging my guitar into the project to try and get sound out that way, the lot.
Frustratingly, but also funnily, the issue was that I’d not connected the -12 power to the opamps
So the power rails at the top had all the right readings but not any of the components from there. Even worse, I had picked up on the fact that there didn’t appear to be any use for -12v, but I just thought that was strange, completely forgetting that TL072s and TL074s require -12 in order to function. So yes, you’d think that after almost 6 months and 11 projects in, I would be able to pick up on this, but I guess 1 row difference on the stripboard is less noticeable.
Anyway, thanks all for your help as always! I wonder if you’re glad when my name pops up on the forum, you probably think to yourself that it’s an easy fix or just something obvious that needs pointing out
