My sought after glory is no longer in the post! I have a neat little stack of 10 black PCBs back from Seeed Studio. At first glance they look alright. Ah, my first child… erm, my first 10 children.
I should point out that since ordering I’ve heard a couple of bad things about Seeed. So I’m going to try out Dirty PCBs next time. On my PCB some of the print screen is a little off, but that doesn’t bother me too much, and I don’t know if that’s down to Seeed botching it or something about KiCAD. Anyway let’s get on with it.
The first thing I did was make sure I got the hole sizes right for the components. The switch, pots and trimpot all seem to fit. Sweet! Past the first hurdle, but I’m still expecting something to have gone wrong, maybe it’s my British disposition.
The first and most important thing is that the PCB works, the next is that it looks good.So what did I miss on the PCB? Well! Now I have it back, there’s a couple of things I might tweak.
First off R3 should really be in line with his buddies R10 etc. I noticed this before the soldering iron was hot.
After populating the PCB with the resistors, diodes, sockets and caps (in that order, because you start with the components with the lowest profiles), no problems there. I had a problem with generating a BOM (bill of materials – a list of components and values) with KiCAD, I tried to solve it by using a download from Saxon, but that didn’t work for me, so I wrote the list out by hand. I double checked the list after a couple of last minute changes to the circuit (nothing worthy of note). There were a couple of values that needed changing. Always double check before you solder anything.
When I finished with the components I flipped the board over to put the pots and switch in. There was a bit of flux on so I thought I’d clean it. When you get little drops of flux on your PCB, you can get rid of them easily with your fingernail or something like this a cotton bud chopped in half!
You always get a bit of flux round the joints so I thought I’d spray a bit of PCB cleaner on and used the firm paper end of the cotton bud to get it off (the fluffy ends just get stuck to the ends of the snipped component legs). It just made the whole situation much worse. I tried a couple of times, but it just ended up covering the whole PCB, so now it’s all a bit claggy. It’s a good job this one is just a trial. It looks awful, see below.
Anyway, after learning my lesson, I proceeded to plonk the pots and switch in. That’s where I noticed a couple more issues. They go in fine, but one thing I hadn’t thought of was that the knobs that I’d planned on using are fairly wide. I really should have thought about this and measured them when I was doing the PCB layout. They’re so close they turn like gears. haha!
Desperate as I was, I tried flipping the two middle pots, which would mean that the tone would work backwards (which I could probably live with), and the blend between the two signals (to be known as ‘bloat’) would be the other way round (couldn’t care less). The only problem was when I tried it…
… I realised that those two knobs would be too close to the footswitches. Back to the drawing board eh.
This was far from a disaster though, and has given me plenty to think about, which coincidentally is the point of this blog. Hopefully you don’t make the same mistakes. you look pretty smart though, so I’m guessing you never would’ve.
So what’s next? Firstly, I need to check that it’s going to work, so I’ll do the offboard wiring, get the enclosure drilled and give it a shot. After that it’s back to KiCAD before I send off for a proper batch.
So on the list for KiCAD is moving that resistor, then I might see about keeping those middle two knobs flipped by rotating their footprint on the PCB (so they work the other way round) and moving them further up the board. I might also see if that gives me space to neaten things up a bit, and get it looking prettier. I have also considered putting the mids switch vertical rather than horizontal. Anyway, that’s for another day and blog post probably.