Mark J. Koch
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markjkoch.bsky.social
Mark J. Koch
@markjkoch.bsky.social
240 followers 310 following 98 posts
Retired Digital Alchemist. Cyber Monk. Technologist. Containment Specialist at -redacted-. Sun Microsystems Labs Alumni. Former SFX specialist at Blue Man Group. Hobbies: Game Design in Java/JavaFX, Analog Synth, PCB design, Robots, Gardening, Cooking.
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markjkoch.bsky.social
A nice way to end the week! Got my #synth module working. Based on an open source design by Hagiwo. #RasPi #Pico2 based and using Arduino libraries, generates waves from tables or math. I added OLED and UI code. I think the PCB components need work as the output looks a little funky. #asmr-synth
October 4, 2025 at 1:20 AM
markjkoch.bsky.social
#synth rack progress! One regulator wouldn't start up, so it took a deeper read into the data sheet to realize I'd missed some components needed for voltages above 5V (a zener and cap). #Zener ended up being a stack of Zeners to achieve desired value. Not my prettiest fix. #pcb #kicad #electronics
My quad output power supply for my Eurorack alternative idea. Many engineers don't know it but you can make a typical buck regulator put out negative voltage if you swap the ground and Vout lines. The Vout is grounded and the common lines inside the circuit will output a negative potential of the desired output voltage. Feels unintuitive when designing, but works well. Also, this design uses the HUSB power negotiation chip to allow the board to be powered with a USB-PD capable laptop supply. Using the HUSB chip, those supplies can negotiate a range of output voltages like 5, 9, 12, 18 and 20V at 3 or more amperes. I'm using 20V in this design to then generate the +15, -15 and 5V needed for analog synthesizer circuits. This bodge is the missing Zener. I needed a zener of around 11.5V but only had some 3.2V laying around. So I hooked four SOT023 type in series to get close to the value I wanted. Kicking myself for not studying the data sheet more at design time. It's right there. The data sheet for this buck regulator shows that for output voltages above 12V, a zener is needed to bring the boost voltage into proper range. Once I did this, the whole thing just worked.
September 27, 2025 at 10:17 PM
markjkoch.bsky.social
I don’t have a #Mouser parts purchasing problem! I can stop any time I want. #kicad #pcb #engineering
September 24, 2025 at 3:05 AM
markjkoch.bsky.social
Upon finding this stainless steel bowl at #ikea that looks suspiciously like a half scale #R2D2 head…. Challenge accepted!
September 20, 2025 at 7:26 PM
markjkoch.bsky.social
My #JLCPCB bounty included my prototype #PCB s for a new type of rack #synth that I am thinking about. Think #eurorack but dragged into the new millennium. Backplane has two #I2C busses, slot detection, and 32 negotiated patch signals. Slightly larger such that old ER modules can nest inside.
ASMR Synth Rack backplane, ten slot, featuring PCI-type edge connectors. Not actually PCI. Mine has four voltages, 18-24V, +15, -15 and 5V. There's two I2C busses, slot detection and 32 undefined "patch" lines. The inserted synth cards can negotiate the use of the patch lines for analog audio/control voltage and digital uses. Back plane can be up to 16 slots. Currently working on a 100% 3D printable chassis design. It will be 100% open source. ASMR two slot backplane for bench development purposes. Prototype ASMR hardware as received from the PCB fabrication service. Bottom is 10 slot backplane. Bottom right is a two slot back plane. Center is three experimental boards: top is a breadboard experimenters board, middle is a power supply (USB-PD in, +/-15V and 5V out) and bottom is an implementation of Hagiwo's amazing MOD2 synth module ( I added a one inch OLED display). Right are two face plates for the rack system: The breadboard PCB faceplate and the power supply faceplate. Example of how the ASMR cards plug into the backplane. A rack chassis will be made soon to bring it all together.
September 16, 2025 at 8:11 PM
markjkoch.bsky.social
Yay! The main #PCB for my MOS #KIM-1 replica arrived today from #JLCPCB! The sub-boards seem to fit. Bringup will take awhile since there's a gross chip-pin-numbering error on one of the smaller boards and I'll have to re-fab it. But I'll be able to partially assemble it and test a few things.
My KIM-1 replica, affectionately named "KIM-1000". An all surface mount version based on the original 1970's schematic. I attempted to add a Cyberpunk-ish style to the edges. My KIM-1 replica, affectionately named "KIM-1000". An all surface mount version based on the original 1970's schematic. I attempted to add a Cyberpunk-ish style to the edges.
September 16, 2025 at 7:51 PM
markjkoch.bsky.social
When your latest #PCB uses a #PCI connector (super dirt cheap) and you want the customer to know that they should not even be tempted to plug it into a PC. I used the connector but the pinout and voltages are nowhere near those of PC Cards. At least the warning will be entertaining. #KiCAD
A Printed Circuit Board with what looks like a PCI connector edge. There is a warning imprinted onto the board that states, "Absolutely NOT PCI! Do NOT attempt to use in a computer. SMOKE, FIRE or SMELLS MAY OCCUR."
September 8, 2025 at 4:38 AM
markjkoch.bsky.social
It's alive! Keypad/Display #PCB module for my #kim-1 replica is working! Mostly based on the original 1970s #schematic, using modern parts. I wrote a PCB test fixture using Arduino and #rp2040 #raspberrypipico module from #adafruit. My first time using a rp2040 was mostly painless. #65C02
August 28, 2025 at 9:20 PM
markjkoch.bsky.social
This is a public service announcement for you to support your local PBS station! #PBS #RickSteves
World Traveller, Rick Steves, as a pickle! Support your local PBS station to keep getting more Rick.
August 15, 2025 at 4:04 PM
markjkoch.bsky.social
OK. Why not? SPOILER ALERT! ... Labeled as "Suggestive" to blur image for those who don't want to see it before it's a real thing.
KiVAD render of the MOS KIM-1000. A modern take on the KIM-1 CPU board from the 1970's. I really wanted one of the original KIM-1 boards as a kid but, being a kid, no money. However, when I reached college, my degree included theory and hands on with our very own Z-80 systems that we got to build using raw components and wire wrap! Worked the same as the KIM-1 and we even had to write our own operating program. The following semester we got to expand our Z-80s with the peripheral of our choice. I built a full robot that I'd already been working on since I was 14-ish. I programmed it to work like the "Big Track" toy. I handed all my original documentation, schematics and code to the professor to get my grade (should have made some photocopies at least). Never did get any of that back. This was a couple years before things like floppy disks and ease of and access to printers.
August 10, 2025 at 3:17 AM
markjkoch.bsky.social
My @oshpark.bsky.social PCBs arrived. They are part of my #kicad project to create a #KIM-1 #65c02 computer replica, with a twist. I started with the original schematic but broke it into SMT modules. Each module is a castellated #PCB "stamp" for a larger main board that I'm finishing up.
August 9, 2025 at 9:14 PM
markjkoch.bsky.social
Fixed it!

github.com/CircuitMonke...

Get a breakout PCB. Just upload to @oshpark.bsky.social
github.com/CircuitMonke...
Break out PCB for a 1/8inch type TRS audio jack. KiCAD library symbol and footprint available via the Circuit Monkey KiCAD libraries. A corrected version of the F**d Up and wonky KiCAD default library for this part.
July 17, 2025 at 9:24 PM
markjkoch.bsky.social
Ughhh! That 2 degree twist on the audio jack. Thanks #kicad! And thus I kick off the official open source version of my custom "tuned" KiCAD library. I can't be that harsh since #EagleCAD included libraries were full of this kind of anomalous shenanigans that gave me trust issues. #PCB
PCB showing the mounted TRS audio jack with a slight 2 degree turn. It turns out that the KiCAD supplied library footprint has multiple inaccurate dimensions.
June 24, 2025 at 10:30 PM
markjkoch.bsky.social
Wrapping up my week by getting some good results from my current project. I got a #Adafruit Qualia #ESP32 dev board which is made for interfacing to the newer IPS LCD displays. It has a touch screen as well! Had to crash learn some #CircuitPython and was able to code a working GUI Widget set.
May 9, 2025 at 5:49 PM
markjkoch.bsky.social
How it feels at the moment....
Fry from Futurama riding a "Scootie-Puff Jr." on his way to save the day.
May 1, 2025 at 5:06 PM
markjkoch.bsky.social
#Amazon sellers never cease to entertain. The idea of Tungsten Carbide blades by "Star Ribs" took me to a whole new place in my demented brain...
May 1, 2025 at 2:40 AM
markjkoch.bsky.social
While my last post involved some nostalgic smut I'd come across in my junk pile, I spent the evening sorting another old relic in my lab space. My 40 year old kit of #electronics parts from college! Everything was jumbled into tackle boxes and I sorted them out. Almost everything is still usable!
From random piles of resistors, capacitors, jumper wires, chips and other electronics prototyping components, I sorted the contents of two tackle boxes into this pile of things that have nice homes in my current sorting system. Now, when I need something specific, I can look in one place instead of many. I'll find some new use for the tackle boxes. The sorted parts were previously jumbled up in these trays with no particular order to them. I left the larger tool items in there for now to show a smidge of the chaos I'd come across.
April 25, 2025 at 4:13 AM
markjkoch.bsky.social
If you're a fan of, or researching #erotica from the early days of the #internet, then you owe it to yourself to track down this edition of Forum magazine which had multiple articles on the emerging use of online #BBS for the #horny folks. #Penthouse Forum December 1988, Vol. 18, Num. 4. #retro
December 1988 edition of Penthouse Forum, a Reader's Digest for horny people. A small sized magazine that was usually chock full of erotic stories and discussions, this particular edition covered the emerging use of "The Newest & Wildest Sex Underground", computers, internet and BBS to share ideas involving subjects of a sexual nature. There's even one article in here that covers the meaning of many online jargon words like "Compusex", "Emoticon", "On Line", "Lurker", "Handle", etc. Of all the old crap I'm throwing out, I'm keeping this one.
April 25, 2025 at 12:51 AM
markjkoch.bsky.social
Took a break from #gamedev the last few weeks to get a hardware idea out of my head. These electronic flowers can be placed into a vase that has voltage wired into two layers that make contact with copper on the stems. #steam #electronics #techart #arduino Thank you to @oshpark.bsky.social
April 21, 2025 at 8:48 PM
markjkoch.bsky.social
#screenshotsaturday time. Worked all week on this one, models in Fusion. One of the final scenes I need to create for the game. High Tech zone takes some finesse to get into, but once there, you can pick up some side money and a new friend in the form of a ROM construct. #gamedev #daz3d #fusion360
High Tech zone is riddled with the monolithic skyscrapers of large corporations. Many of the lobbies have cyberspace jacks for you to borrow escalated access to the site zones you need to reach. Make some side money in exchange for a brief medical procedure. Stop by Sense Net to rescue your new friend out of cold storage, if you have the locker code.
March 30, 2025 at 4:51 AM
markjkoch.bsky.social
Maybe I should start doing album covers for synth bands?
Fictional album cover for a well known synth artist.
March 22, 2025 at 12:10 AM
markjkoch.bsky.social
This week's WIP. My interpretation of the #Neuromancer bust which is also a terminal for communicating with the Neuromancer AI. The player eventually makes their way to the Villa Straylight on the Freeside space station to chat with it. Made in Fusion and shaded in Daz3D. #gamedev #cyberpunk #daz3d
Brought the top part of a Daz3D figure into Fusion and started cutting and popping tech shapes into it and onto it using the parametric tools. Used false colors to designate and tag the shader surfaces in Fusion. Assign textured shaders to each surface.
March 21, 2025 at 8:01 PM
markjkoch.bsky.social
And while you're here, might as well get the kids tagged. They got any Pokemon tattoos?
You're on a space station. Might as well get a fancy Yakuza style tattoo on your hind side.
March 16, 2025 at 10:15 PM
markjkoch.bsky.social
#screenshotsaturday bled over into Sunday as my renders took a good hour each. So here's some of the other space station renders. One of the banks has a manager office you need to get into but has a nice view. Maybe pick up some space snacks next door? #neuromancer #gamedev #cyberpunk
Bank manager is not here. I guess that means I can use the cyberspace jack for a while? This bank reminds me of a nice Swiss city.... This section of the space station has another bank and a place to pick up some snacks. All that space travel gives me the hungries.... Wandering down some more of the space stations tubes. Is that a convenience store? I need a 32oz. soda right now.
March 16, 2025 at 10:13 PM
markjkoch.bsky.social
If you ignore the polite signs to keep out, you can make your way to the Villa Straylight and see if any one is home. Don't be a porch pirate!
Would you walk alone down this hallway? Stanley Kubrick is rolling over in his grave. Did I nail it Stan? No soliciting means knock louder right? Can Wintermute come out to play? I have ice cream.
March 16, 2025 at 6:47 AM