Not quite functional!

Made two yusynth VCOs the other day.. None works... But the real problem is that at the schematics it mentions using a 1% silver mica capacitor. I have used plain ceramic and multilayer. Voltages are OK. The comparator and OP Amps get nice voltages. No electrolytic capacitors are the other way around. So it has to be this. While I wait for the silver micas, I might put together a yusynth moog filter clone.
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AVR Synth RE-re-packaged

Went today to the electronics shop to get some cheap stuff for the yusynth and saw this box for 6 euros. From what you can see, I got it. It is relatively small with a panel area of 15x9cm.

So I went on to repackage my avrSynth16 I had build sometime ago.

There was a failed attempt to house the synth inside a FIRA drawer from IKEA but the design had some flaws (And it was way to big to have it around).

The first step was to make a 15x9cm layout in inkscape and make objects that were the size of the underside of the components I would use. So I could layout the knobs and switches knowing that they'll fit. Purple were the knobs, cyan were the switches.

I made the holes with my newly aquired tools that I mentioned in earlier posts (the step drill that is) and had the panel ready for sticking the graphics.

Since the step drill went up to 12mm diameter, the midi socket hole that needed 15mm diameter, got a little help from my old (t)rusty reamer. (I always had that tool! It belonged to my father from what I vaguely remember)

The simple design is always the best. Made in inkscape. (Super drawing program, open source!)

The time of the knob transplant was stressful. A few wires came loose. (The design is not so clean from what you can see)

So it was obvious that it would end like this.. A big spaghetti bundle.

The hardest job was to fit the boards inside the box. It took a lot of careful squeezing and pulling/pushing wires inside the box. This was done while the synth was playing from a sequencer. It kinda reminded me of some brain surgeries you see on TV where the patient is placed on the bed with an open head, and the doctors have electrodes touching his brains to see what is the problem. When the synth stopped responding I stopped pushing!!

You can see that the panel has a slight bulge at the center..

And now the publicity shots!

Yusynth modular

New parallel project starts: The yusynth modular.

this is based on this which is a rather easy DIY set of modules.

The boards are etched, some even drilled, the panels are made (that means that someone else will make them for me, I just drawed (eg designed) them) and the components have arrived (very cheap postage fees to where I live and all components required for this project available..).

Will get some photos of the panels once made.

For now, there is always Braska, lurking in the shadows of DIY.

Basic modules are made: 2 VCOs, 2 LFOs, an ADSR, a VCA, 2 Filters for starters (and the psu that has already been made)

Now I will have to make a case for it.. :(

Making panel holes

Making holes for panel pots and switches has always been a major pain in the butt for me.
I tried lots of times to make different sized holes with standard metal drills on tin sheets but the holes always came out at the wrong places or, due to the fact that I don't have a drill stand, triangle shaped because of my inability to keep the panels from sliding up and down the drill. They also came out with lots of scrap attached to them (I cannot find the right word but I mean the metal goo that remains at the opposite side of the drill entrance).

Today, I received in the mail a... STEP DRILL!

Didn't know it's existence till recently but using it has been a revelation!!!

Also I got three tools to make the holes tapered (the smaller two are pictured).

If you are careful with the step drill you get instant holes at the desired diameter (the numbers on the drill are mm). And since there is a taper leading to the next, larger diameter on the drill, you get instant metal-goo cleaning and flattening. No more scrap at the holes...

The following is a 5mm hole. No other tools used!

Below is a 5mm hole but treated with the taper tool afterwards. You can house nicely a 3 or 4mm screw with tapered head.

And the big one.. 10mm for audio jacks and some cheap pots. Instant gratification.

Same rules apply though. If you want to be as exact as possible, first start with a small drill (eg 2mm) to mark the center so as the step drill has somewhere to land.

I would really like to know how other people make their panels and especialy the square shaped holes. This has always been a mystery to me :)


Fixing the MC-909 rotary encoder

And of course taking a peek at its guts to shoot some porn in the process:

This is the MC-909.. It is my favourite synth because it allows a hands-on approach to sound synthesis. Even if it is targetet to the DJ market (which I am not!), it is capable of very interesting textures (and it has a nice sampler even if it lacks the velocity and key multilayering of the high-end samplers)

I got it second hand from ebay and since day one, the rotary encoder had a slight problem. I had to turn it slow to register correct values. If I rotated it quickly it would jump 5-6 values behind every 5-6 values (so it didn't go anywhere).

I decided that I would fix it and gutted the machine.. pictures follow:

The faulty encoder can be seen in the following picture:

The pads are velocity sensitive and this is how it works: there are two contact areas
and the rubber pads have the graphite layer that correspond to these two areas in different heights. So when you hit the pad, the MC measures the time it took to close both switches which corresponds to the velocity of your hand.

This is the encoder. Close ups:

The part can be found at mouser as 688-EC12E2420802 (alps 12mm rotary encoder) and it costs only 2 bucks. It is very simple to replace it, you must have a solder pump though to cleanly remove it.

Things to remember:

*) when you unscrew the machine, make a note (NOT mental) to the whereabouts of each screw..
*) the order of removing the components is the following: 1. the PSU, 2. the IO board, 3. the sound engine, 4. the "DJ" slider (the big one), 5. the mains outlet and 6. the main board.

some connections (eg the one marked with x) need not be disconnected. You can put the IO board aside for a while.

Good luck if you have the same problem.

Good choice if you have an MC-909 instead of an MC-808 :)

Now my MC-909 is like new.