SynthesizerKeith

Synthesizer repair technician. Synthesizers and success.

[SynthesizerKeith @SynthKeith]

Follow me on a wild journey: restoring an EMS VCS3 and DK1 keyboard. In this massive 4-part video thread, I'll tear down the VCS3, make lots of cool noise, and end in a funky track. Follow along for the revival! #Synthesizer #VintageSynth #SynthRepair #VCS3

[SynthesizerKeith @SynthKeith]

@blind_via Synth tech here. Please don't stop posting audio related info. Your tech tips are gold!

[SynthesizerKeith @SynthKeith]

I just added individual outputs on this vintage Roland TR-77 drum machine for bass, snare, and hi-hats. Check out that daughter-board near the jacks. It sounds like a branch new machine, crisp and clear, and you can add effects on individual voices now. #SynthTech #SynthRepair

[SynthesizerKeith @SynthKeith]

@MakeAugusta Earl Nightingale is one of my mentors. "You become what you think about." It's true, and it works.

[SynthesizerKeith @SynthKeith]

This is the perfect circuit for my ARP Odyssey Synthesizer, MIDI retrofit board. The Odyssey's ADSR envelope needs both a long gate (the rising edge), and a trigger (the short pulse) to function correctly.

[ElectronicsNotes by Ian Poole @ElecNotes]

Back to Basics: Creating Short Pulses with Simple Transistor Circuits

Sometimes the best solution to a design challenge isn't a complex IC or a microcontroller—it’s a handful of discrete components and a fundamental understanding of circuit behaviour.

If you’ve ever needed to trigger a logic circuit or generate a timing pulse from the edge of a square wave, a Transistor Pulse Generator is a tool every engineer should have in their back pocket.

In my latest summary, I explore how to design these using simple Bipolar Junction Transistors (BJTs).

How it works:
The key combination is a CR (Capacitor-Resistor) network acting as a differentiator. When a rising edge hits the network, the capacitor passes a brief "spike" as it charges.

By pairing this with a transistor, we can:

✅ Clean up the pulse into a sharp, usable square wave.

✅ Remove unwanted negative-going spikes.

✅ Invert or maintain the polarity of the input signal.

Two configurations to consider:
1. The One-Transistor Design: Ideal for simplicity, providing a negative-going pulse from a positive-going input.
2. The Two-Transistor Non-Inverting Design: Uses two capacitively coupled NPN switches to create a positive pulse from a rising edge—a common requirement for TTL logic.

A Quick Tip for the Workbench:
When designing the two-transistor version, be mindful of your rail voltage! If it exceeds ~7V, the negative voltage spike at the base-emitter junction could cause a breakdown. Keeping it around 5V (standard logic level) is the "sweet spot" for reliability.

Discrete designs like these remind us that even in an age of SOCs, there is still immense value in straightforward, cost-effective analog building blocks.

Want more information? Check the link in the comments.

#ElectronicsEngineering #CircuitDesign #EmbeddedSystems #AnalogElectronics #ElectricalEngineering #EngineeringTips

[SynthesizerKeith @SynthKeith]

@blind_via The tips help me out quite a lot, because PCB layout isn't my main gig. It's good just to be immersed in the jargon.

[SynthesizerKeith @SynthKeith]

@blind_via This is a golden tip for me. Just starting a dense PCB layout. Thanks.

[SynthesizerKeith @SynthKeith]

@cqcqcqdx This started everything for me. EVERYTHING!

[maker.io @MakerIO]

Maker Tutorial - Op-Amp Wonders: Circuit Secrets Revealed!

More here: https://t.co/rYEg47to8C

#electronics #tutorial

[SynthesizerKeith @SynthKeith]

I just brought this Nord Electro 3 back to life by cleaning the key contacts. Dead keys on your vintage synthesizer? It's usually dirt, corrosion, and time. #SynthTech #SynthRepair

[SynthesizerKeith @SynthKeith]

My full Yamaha DX7 synth repair video is live. New front overlay, new tact switches, battery swap, keyboard cleaning, wiring fix-up, the works. Lots of details for synthesizer nerds.

[SynthesizerKeith @SynthKeith]

Is the DSR-2000 the most under rated of the Yamaha FM synthesizers? Here is some proof. #SynthRepair #SynthTech #Yamaha #DSR2000 #FM #Synthesizer

[SynthesizerKeith @SynthKeith]

@MakeAugusta I used one of these at the Ontario Science Centre in the early 1980s. It was running a Lunar Lander program. I still remember that cool keyboard. And yes, it was amazing!

[SynthesizerKeith @SynthKeith]

It's not every day that Mark Mothersbaugh and Josh Hager (Josh2) from @DEVO pose with your business card. The show last night in Toronto was outstanding! #DEVO #SynthTech #SynthRepair

[SynthesizerKeith @SynthKeith]

I'm in the middle of repairing this fantastic Roland System 100 Modular Synthesizer. I just got both (yes, there are two) sequencers going, and decided to channel some Giorgio Moroder. More to come on this repair... #SynthRepair #SynthTech #Roland

[SynthesizerKeith @SynthKeith]

Tape echo has a charm that can't be duplicated. I repaired a noisy pre-amp circuit in this Korg Stage Echo SE-300, cleaned the tape path, demagnetized the heads, and replaced the tape loop. It even has a built-in spring reverb! #SynthRepair #SynthTech #TapeEcho #Korg

[SynthesizerKeith @SynthKeith]

I'm reparing this vintage Yamaha DX7 synthesizer. The front panel is trashed, so the first thing is to replace the overlay. Precision is a must! Stay tuned for the rest of the restoration. #SynthRepair #SynthTech #DX7

[SynthesizerKeith @SynthKeith]

I just added a sync-in jack to this Electro-Harmonix DRM16 drum machine. I'm syncing it to my Kawai R-100, and then through MIDI to my MPC Live. Super funky! There is some audio trickery happening here. See if you can spot it! #SynthRepair #SynthTech #DrumMachine

[SynthesizerKeith @SynthKeith]

Fixed this LinnDrum's toms issue! The toms had a loud click. Traced it to faulty EPROMs. Burned a fresh pair, and now they sound clean and punchy. I keep vintage gear working! #LinnDrum #SynthRepair #SynthTech #DrumMachine