Category Archives: Retro Modding

Upgrading those little LED reading lamps

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Those rechargeable reading lamps are really nice, a pity they don’t last longer. But you can make them. It’s super simple – just add a second rechargeable battery.

These lamps are being sold by a couple of different Chinese manufacturers. Some have only one type of LED, some have two – for different lighting colours – and they all have a touch-sensitive top as power switch, charge via USB-C port, and are 40cm high. 

And they seem to have one other thing in common: they have room for a second battery. At least the three different types I opened did.

It doesn’t get any easier: Order battery, solder connector, insert…

Some of them even have a second battery charger terminal, like the one I modified in the video. Others don’t; there you can just add the second battery in parallel or, if you are less adventurous concerning the charging circuitry, remove the first battery.

The battery type used is a standard single18650 Li-Ion cell; rechargeable, with 3.7V voltage. The lamps usually hold one of those, offering 2400mAh of charge, but there are also affordable types that last longer, like this Samsung INR18650 with soldering pads (no affiliate link, order them wherever you like.) Just ordered a couple, as I am also planning to upgrade my new Digitakt.

Battery holder with second battery next to it, connector and cable soldered to it

So this is about as simple as it gets: open lamp, unpack battery, solder connector to the battery without overheating it – this is where the solder pads come in handy – remove first battery, plug in connector, test lamp, plug in second connector, test again, reassemble lamp, make wife happy.

…and I hadn’t realized that you can dim them!

It is a bit embarrassing but it took a hint from my daughter for me to realize that these lamps also have a dimmer function. If you keep your finger on the touch-sensitive switch, the brightness will decrease, then increase.

Stereoping Hardware Controller for Crumar Bit

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Stephan (aka umusic6) did some nice work:

Thanks to his efforts, there is now a Bit Edition of Stereoping’s Synth Controller, for Crumar Bit-01/One/99 with the Tauntek firmware. You can read up on the firmware, or order it, here.

(No, this is not an affiliate link, I have no share in this. But I think it’s a great project.)

Midifying Jenny, Step 1: Replacing the old keyboard chip with a Teensy

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This is the first post in a series of small projects for retrofitting my JEN SX-1000 monosynth with a simple and cheap MIDI interface controller. Read about the basic idea here. Today, I am designing and building the micro-controller brain of the Jenny retrofit – if you are capable of basic soldering, it should not take you more than two hours and a couple of very common electronic parts.

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Jenny getting her very own phaser…

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…and my sweet Lord, does it make her shine!

Nothing fancy here. After inserting the booster/overdrive in between VCO and filter section, I took another of those lovely Musikding.de kits for a phaser, built it, drilled some holes into Jenny’s housing and fitted it.

I have been using Jenny as a bass synth recently, and I am quite impressed by the quantities of life and fun this old machine is adding to the mix. She doesn’t do that much in terms of tonal range, but what she does, she does well.

Drilling holes in Jenny’s front

I rediscovered an old trick when drilling metal: use a bit of alcohol, not on the person drilling, but on the surface you want to drill. And don’t go too fast.

V2.0: A Teensy-based MIDI Controller

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Building my own wheels for the Launchpad Pro – once again, with style.

Two weeks ago, I started a little sunday afternoon project, sucessfully building my first own MIDI controller – a pitch bend/mod wheel/midi merge device to serve as a companion to my new Launchpad Pro. Using an Arduino, a prototyping board by SparkFun, and community-made code, I succeeded with surprisingly little effort – the most time-consuming part was finding and fixing the errors I had clumsily soldered into my pathetic excuse for a MIDI interface. But it worked!

Launchpad Companion Controller in actionAs they say, the worst thing that can happen is that you succeed. The quick and easy success made me hungry for more – I started a MIDIfication project for my JEN SX-1000 monophonic synth, based on a Teensy, another microcontroller board that can be used within the Arduino development eco-system but is much better suited to MIDI/USB applications.

V2.0: A Teensy-based MIDI controller

This is actually a side project to that. I looked at my self-made controller and noticed that it is usable but not very playable – I wanted real wheels for the Launchpad, not sliders. So I decided to redo a V2.0 of the controller, based on the Teensy.

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MIDIfying Jenny – A Call To Arms

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Isn’t it about time my beloved Jenny got her own MIDI interface?

JEN SX-1000 front with ATMEGA chip

To be sure, microcontroller-based interfaces for the JEN SX-1000 do exist. Apart from the commercial CV/Gate solutions by Kenton, there is Neil Johnson’s keyboard interface design. But even if you can get hold of the PCB – a supplier in the JEN SX-1000 group on Facebook had a batch made – the design has an intimidating parts list, and takes some serious time to build.

Is it possible to do it simpler? Emboldened by my success building a small Arduino-based MIDI controller, I decided to start a midification effort that is

  • easy to do (requiring only basic soldering skills, if any)
  • easy to get (by using components that you can buy on Amazon if you have to),
  • easy to develop (using standard solutions from the Arduino community),
  • easy to schedule (because the project is divided up into little steps, each of which is a small afternoon sub-project with instant gratification),
  • easy to participate (by contributing own ideas and code for parts of the project).

I will describe the basic layout of the MIDI upgrade kit project here. Each step, i.e. each sub-project, will then be treated in a new post, depending how fast I (or the community) get them done.

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“We apologize for the inconvenience.”

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Ford Prefect and Arthur Dent - still from the BBC series

You may know these two gentlemen. If not, grab your VHS player, rent out the BBC’s “Hitchhiker’s Guide” series, watch. Hurry!


If you have tried to send a message, or use the shop, you may have noticed that it did not work in the last two days – or, you didn’t notice, and are still waiting for an answer. A conflict between the Contact Form 7 plugin, which I have rediscovered, and the WP Cerber security plugin made some readjustments necessary. It should all be fine again now.

On the plus side, I had the opportunity to overhaul my shop pages, so if you are interested in an update for the Akai AX-80 or Kawai SX-240, it is easier to find and order. Concerning the Matrix-6, there is news: A very old bug in the firmware has finally been found and eliminated; it made it impossible to set negative DETUNE (parameter 12) values. Oddly enough, nobody except Gregor from Stereoping ever seems to have noticed, so there is no harm in continuing to use the firmware V2.14.

There is a new version V2.15 though – Bob fixed the bug – so if you feel that you need negative detune values, you may order that. Or you may take the opportunity to buy one of the V2.14 firmware PROMs extra cheap – while stocks last.

A love letter to Jenny: Tremolo and Key Tracking Mod

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This JEN SX-1000 belongs to Stéphane in France, who wrote to tell me of the three mods he did. I have never seen two of them before – a Tremolo control, and variable filter tracking. Which would make Gordon Reid very, very happy.

So here is Stéphane’s letter:

“Hello, here are some modifications for the Jen synthetone SX1000. Nothing is disconnected. Components are added.”

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A new glide pot for Jenny

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A bit of TLC for my oldest synthesizer: Jenny is getting a new potentiometer. As the synth’s pots were rather cheap, open types that gather dust, and are 40 years old now, they have become all scratchy and jumpy. As I have mentioned before, I am not the greatest fan of Kontakt spray and similar solvents/cleaners, so I bought replacements. But I never found the time to actually replace them.

JEN SX-1000's

This knob is a good place to start: The “glide” potentiometer is in charge of portamento, and it is one of the first things that might make Jenny fail (see Neil Johnson’s site). A faulty glide pot means that the synth will only ever play the same note regardless of which key you press. So I did replace that pot, which is pretty straightforward – you’ll find some pictures in this gallery. (It is a 2.2M linear type BTW.)

Overview of potentiometer values

This is an overview of the potentiometer values, some of them are linear, some logarithmic, a few antilog. The most obvious candidates for replacement, apart from the glide pot, would be Frequency (100k) and Resonance (100k) for the filter, and Tune (10k).

Whitening Jenny’s smile: Bleaching old synth keys

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Jenny – my old 70s monosynth – is a beauty, and I love her knobby face. Her smile, though, has yellowed over the decades. So to make Jenny even more attractive, I decided to try and bleach the keys with hydrogen peroxide.

TL;DR: Effect has been minimal, so it’s probably not worth it. But it was fun. If you try it, make the Retrobright bleaching gel, don’t use a hydrogen peroxide bath. And have a good UV source.

Old keys with a slightly newer key on top of them

Jenny’s keyboard compared to a key from a mid-80s Roland JX8P synth

In School, I used to hate chemistry. Did I mention that I used to hate chemistry? Okay, I did (when successfully reviving Jenny’s keyboard contact springs by cooking them)

So here’s what I did.

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