I started a new project on GitHub, an open-source waveshaper/bithcrusher pedal. It’s now reached it’s first complete version, you should check it out:
A broken CDrom is a perfect candidate for a simple and cheap etchant agitator. What’s an etchant agitator? It’s a device that makes the etchant (Ferric chloride, for example) move around the container when etching PCBs. Why? It greatly speeds up etching, by washing away the top layer of corroded copper, exposing clean copper to be etched.
I’ve seen many CD tray etchant agitators online, but all of them are too expensive and/or too complicated. Using integrated H-bridges and microcontrollers or decade counters for such a simple design is totaly overkill to me. Here’s one example, showing operation:
(operation at 3:57)
I had some 4096s (Schmitt trigger NAND gate) lying around (and they’re better than 555s when it comes to symmetrical duty cycle squarewaves), and I decided to design the cheapest, simplest, lowest-component-count CD tray etchant agitator. While some might wonder why I didn’t go with a 555, I’d have to use an inverter anyway, and 555s suck at symmetric-duty-cycle operation.
The circuit consists of a squarewave oscillator made with a single 4096 gate, a (logical) inverter made with another 4096 gate (needed by H-bridge) and a simple, common transistor H-bridge with some protection. Hookup is really simple, as you can see. The circuit can be easily modified to use a quad NOR gate or an inverter, as long as they have Schmitt trigger inputs.
You can replace R1 with a 100k linear pot (wired as a variable resistor) in series with a 20k resistor, for 170ms to 1s period adjustment.
The price should be under 2€.
Here’s the PDF, including a schematic, layout and PCB:
This is a wiring I’ve made by combining various Tele wirings from the internet. The goal was to have individual tone controls and a series mode, without destroying the classic Tele look. The series mode had to be easily accessible to be practical, which led me to choose a push-push pot which switches the guitar into series mode regardless of the position of the 3-way switch. Tele is a guitar that benefits the most from individual tone pots.
The tone controls are Gibson-like, hence the need for no-load mod, to prevent disproportional tone-sucking in the middle position. The upper pot influences the neck pickup, the lower influences the bridge pickup, and both are active in the middle position.
There is a great feature that came to be completely unintentionally: when wired in series, the bridge tone control affects only the bridge pickup, while the neck pup affects both. This results with ‘bridge tone’ pot being a sort of humbucker color knob, having several distinct sounds through its range – from p90ish to fat, middy humbucker. It actually works in an inverse fashion – it’s treblier counter clockwise. I hope I’ll have some time soon to demo this unique feature!
I’ve used this wiring extensively on my handmade tele by Nikola for the last 3 years. Here’s how it looks installed:
Here’s the link to the PDF: