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Welcome to Stefan Vorkoetter’s web site! I’m a private pilot and model aviation hobbyist, slide rule, calculator, fountain pen, and watch collector, electronics hobbyist, Hammond organ enthusiast, and software developer living on a Fjord horse farm in Ontario, Canada. This page is a gateway to the ever growing collection of articles I like to write describing my projects and hobbies. If your interests coincide at all with mine, I’m sure you’ll find something useful here.

June 28, 2017

A Compact Home-Made Raspberry Pi Tablet  NEW 

A homemade compact Raspberry Pi based tablet.

After recently discovering the Raspberry Pi and its matching 7-inch touchscreen, the first thing that popped into my head was that I could build a tablet. Mine certainly isn’t the first Pi-based tablet, as Googling “Raspberry Pi Tablet” will reveal, but I believe it to be the smallest and lightest so far. This was a make-it-up-as-I-go project, and this article is as much about the journey as the end result.


Electronics Reviews

Electronics Reviews

In-depth tests, reviews, and discussion of batteries, chargers, computers, and gadgets I use.

Electronic Projects and Techniques

Electronic Projects

DIY projects and advice for hobbyists, experimenters, musicians, and aviators.

Electric R/C Airplanes

Electric R/C Airplanes

Over 50 articles demystifying the design, construction, theory, and practice of electric R/C planes.

General Aviation

General Aviation

Aircraft, pilot gear, aerial photography, flight reports, and all things aviation!

Building an Evans VP-1 “Volksplane”

Building a Volksplane

Follow my progress in words and pictures as I build an Evans single seat VW powered Volksplane.

Hammond Tonewheel Organs

Hammond Organs

Understanding, maintaining, and modifying the Hammond tone-wheel and vacuum tube organ.

Vintage Calculators

Vintage Calculators

Repair, programming, and use of HP programmable calculators from the 1970s to today.

Slide Rules

Slide Rules

My collection of slip-sticks and whiz-wheels, the calculating tool of choice for 350 years.

Fountain Pens and Mechanical Watches

Pens and Watches

Vintage and modern fountain pens, inks, paper, and mechanical wrist watches.

Miscellaneous Articles

Miscellanous Articles

Articles and papers on other topics that just don't fit neatly into any of the categories above.

The finished amplifier, ready for reinstallation in the organ.

I’ve owned my Hammond organ for eight years now, and although working quite well, there was still an unresolved issue of a rumbling or rushing sound, whether or not anything was being played at the time. Such sounds in old equipment are often caused by degrading carbon resistors. Rather than attempt to isolate and replace the problematic resistors, I decided to rebuild from the ground up.


This is how engineering calculations were done for 350 years, ending in the mid 1970s.

I’ve been collecting slide rules since 2007, and until now, have kept my collection in a large shoebox in a drawer. I have been wanting to build a proper display case for them for a few years now, and finally got this project underway over the 2015 Christmas holiday. The glass is in a removable frame, making it easy to access the slide rules to use or show to friends.


The Vortix Wake-O-Matic, a retro styled analog musical sunrise alarm clock.

For the past twenty years, I’ve been waking up to an LED alarm clock, but the large glowing red digits disturb my sleep. As both an electronic hobbyist and amateur watchmaker, I decided to build my own new alarm clock, with luminous analog dial, gradual wake-up beginning with soft lights simulating a sunrise, and a random music generator instead of an annoying beeper or irritating radio chatter.


The eight tone generators of the Chord EGG 2015

The Stereo Chord EGG was a novel little circuit introduced in kit form by PAiA in 1976 as an interesting application of a then-new top octave generator chip. This kit hasn’t been produced in decades, and commands a premium when one does turn up. Because I recently had an application for this random “music” generator, I decided to redesign it from scratch, reusing as much of the existing design as possible, but staying away from proprietary parts.


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