Not necessarily a "build", but a somewhat repair job and I also added a small mod.
The following pictures are from a no name 5W Guitar Training Amp
that's been sitting on my shelf for quite a while now (it's not mine, it's one of a couple of devices/instruments that were given into my care and hasn't been picked up since). The main issue why I never used it: the potentiometers were worn out. I did not even dare look at it without the amp exploding in scratchy noise. Using it without hearing protection was not a good idea. So it remained on the shelf, and started to waste space. Prior to that, the owner hasn't used it in ages either (neither did he care much). After nearly 5 years of collecting dust at my place, I had enough - and I needed a distraction anyway.
So I completely put this thing apart (wouldn't have gotten to the circuit board otherwise) and then not only exchanged the potentiometers (had to widen the holes a bit as well, though it turned out I could have gotten 1:1 replacements - but one of the employees at Conrad, Germany had a different opinion!), redid some solder joints and some of the wiring (mainly the one to the speaker driver), but also added a slight mod where I can now disconnect the hardwired speaker to connect a different one or an attenuator/a loadbox instead.
This thing is still scratchy and jumpy, the input gain and volume correlation makes no sense, I can't raise the tone to higher than 5 (12o'clock) else this thing starts to squeal. But at least it's not completely wasting space anymore.
I also realized that I didn't need the dip switch, since the 1/4" TS jack that was sold to me had a NC function (normally closed), which I saw way too late. But since it was only a couple of cents, I ignored that and added the switch anyway (looks more "technical"). Had so many of them lying around that would have never been used otherwise. Looks like, communication at the hardware store is key. Some people do pay attention to detail and ask questions, some just give a flying F and give you what they think is a suitable replacement. I think I got the latter this time around - which is always annoying of course (unnecessary extra work).
Anyway - pictures.
After widening the holes and adding two more for a switch and a 1/4" TS jack
Finished soldering job:
(this is where I also realized, that this amp has been opened way before my time - the PSU was cut of, and badly "soldered back together", the circuit board also had very bad soldering spots)
This was after I put everything together again:
Not beautiful, neither perfect. Read: I didn't fix all issues - only changed the potentiometers, else I wouldn't have been able to even "listen" what's going on with this device. I do have a suspicion that either the transistor or one of the capacitors is still broken/worn out. Though I'll probably never open this thing up anymore - just not worth it. But if I'm not in the mood to fire up the PC (DI, software - all bells and whistles) and just want to train some chords, or want to create some insane noises with an "external distortion device" (which this thing really isn't - it's not even crunchy in tone!) - then this thing is usable again.
Occupied a couple hours of my time (in both a good and bad way - think 6 hours incl. breaks - hated drilling the holes with a cordless drill driver), I could brush up my skills. Really lightened my mood, and I could easily repair something without pulling my hairs out.
At least one project out of of many planned DIY ones that got finished - even if it took me years. Success!
On to the next one...