I have been accumulating bits and parts for several months now in an attempt to begin my own modular setup and I thought I would share my journey here - as well as perhaps get some much needed help!
My interest began when my job at an escape room closed due to COVID. One piece of my severance package was this fully functioning little beauty:
I also as I mentioned in other threads I had a couple of PC PSU’s lying around that I didnt have a home for. I figured this was as good a jumping off point as any for me to take a stab at DIY synthesis.
This lead to the creation of this setup:
An ATX style connection has two +12 connections one -12 and a plethora of grounds - which I simply attached to the stripboard, splitting off the -12 onto two separate rails.
After a bit of research I found out that PC power supplies will not turn on unless you short pin 16. I wired a switch for this. Sadly my high hopes were dashed as the setup did not work - or so I believe. Exactly why it did not is still a question. I think the problem was not this setup, but instead what I was trying to plug into it. They powered on fine with my test rig here - but as soon as I hooked up my VCO (which we will get to shortly), both power supplies would behave in exactly the same way and turn off instantly. I just assumed it was because they were not happy about providing the necessary -12v since they seemed to be capable in all other respects. In the aftermath of this failure I took the older of the two PSU’s apart with the intention of using the plug socket and heatsinks. Its not a great loss as the fan was dead on it and it was the older of the two.
This brings me to my current problem(s). I have been trying to make the simple VCO and have been having some issues.
Being the type of person I am, I attempted the more complicated build with the square wave and PWM modules first. This was what was originally making the PSU’s turn off.
At first I attributed my failure at attempting something too ambitious, so I started over on the simple design without the extra bits.
I ended up with exactly the same problem. When I hook everything up, I get no buzz and the TL072 get SUPER hot.
This is the test rig I have set up:
(thanks to @Bitnik for this suggestion since I am currently waiting on my FC supply to arrive). It seems to provide +/-9.3v.
Now comes the part where I ask for help! I was really wishing I wouldn’t have to, but I have the feeling I am missing something fundamental and (hopefully) easy to overlook. I took the IC’s out and ran through all of the pins with my voltmeter if this helps at all:
Any help is appreciated because I have a few other related projects waiting in the wings. I have been pluging away at this for a while now and could really use a win XD