Midified CR78 and TR606 sound demos

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Here are two sound demos of a TR606 and a CR78 I midified.

Note the full velocity sensitivity capability of the 606 and the pseudo-velocity sensitivity of the CR78.

TR606:

CR78:

Some more infos about the CR78 mod:

Depending on the midi velocity sent to the device, the master volume is adjusted. That is of course not the same as full velocity sensitivity, but gives you a surprisingly great amount of flexibility. Think of the 808 for example which has one accent track – this is similar, but you can adjust the accent on the fly.

Repairing a Novation Supernova with an overvoltage damage

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This Novation Supernova just came in.

probably due to overvoltage on one of the outputs two of the outputs failed.

Which is actually really lucky, take a look at the damage!

This is the bottom side of the PCB, the trace coming from the connector vaporized and you can see how much heat must have been there: A large area of the solder resist is gone too. If you look closely you can see, that the trace actually fused with the surrounding ground plane. I believe this is what saved the Supernova, because it protected the rest of the circuitry from the high voltage.

Novation Supernova (2)

This is the other side. I already desoldered the connectors. As you can see there was a lot of heat here, too, the trace acted like a fuse and melted and the 47Ohms resistor exploded. Wow!

Novation Supernova (1)

These are scorch marks on the metal enclosure which was about 1cm away from the PCB.

Novation Supernova (3)

Apart from that only some more resistors and an op-amp failed. Amazing when you consider what must have happened here!

I replaced the broken SMD components, redid the broken traces and the two outputs are working again 🙂

Novation Supernova (8)

In the picture above you can see the replaced opamp and some replaced resistors. Unfortunately I didn’t notice a broken 740 ohms resistor before I ordered the parts. I used wired one instead, doesn’t look as nice, but works as well.

 

 

A new power supply for a Yamaha DX21

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Look at this horrible “repair” job someone did to the power supply of this Yamaha DX21 (which broke again of course)

The main electrolytic capacitor has been replaced with just some other one, definitely not a low-ESR type, connected with quite long and thin leads and then glued into place somewhere in the case. The switching transistor is glued into place too and the traces leading to it are almost, but just not quite broken.Yamaha DX21 (3)

An additional power LED had been added, but instead of connecting it to the 5V rail, it is connected directly to 230V via an capacitive “led power supply”.

Yamaha DX21 (2)

Last but not least there is some strange sticky stuff all over the place, might be electrolyte from the capacitor, or some kind of glue that was used for something. It is hard to tell, it is an awful mess in there. Yamaha DX21 (1)

In cases like this instead of trying to fix the existing power supply it is better and cheaper to replace it with a new one.

Yamaha DX21 (4)

 

 

Sequential Tom power supply

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This Sequential Tom needed a new power supply. It states to need 15V AC, but after a little bit of reverse engineering it turned out to actually need 2×7.5V AC. It is quite unlikely to find a wall adapter with 2×7.5V AC, so I had to build an own power supply. It is just a (fused) transformer in a case, and a plug attached to a cable that fits into the back of the Tom. Done 🙂

sequential tom (2)

4x Midi CV Interface rev.2

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While waiting for my Polysix mod PCB, I am working on rev. 2 of my midi to cv interface. Rev 1 was working well, but I realized I wanted some more features.

midi2cv4

The new one will have:

  • 4 x CV out, 12 bit precision each
  • 4x Gate
  • Glide / portamento control for CV outs
  • For each CV you can switch glide mode between (on/auto/off)
  • For CV 3/4 you can choose individually whether they output midi notes or midi velocity from CV 1/2
  • Each CV can be controlled by midi notes and midi controller
  • FM in
  • Midi learn
  • Leds for gate and CV out
  • Doesn’t use smd parts an can be built by everyone

This basically enables you to have 4x polyphony with a modular synthesizer !…..and much more 🙂

 

Polysix Mod PCB coming soon

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I am currently working on a PCB / kit for my Korg  Polysix mod. It will be available soon and feature both mods: portamento and spread detune.

This is a design for a front panel – Polysix style:

p6moddesign

It could look like this:

p6moddesign2

And here is a rendering of the PCB:

p6 spread detune pcb

Currently a prototype board is being produced, for some last checks before a larger order of boards.

If you are interested, have any suggestions or questions, let me know in the comments 🙂