Misa's Yocto blog

in February 2014 I ordered a "Yocto", a pretty close clone of the old drum machine classic Roland TR-808. But you already knew that -- otherwise you probably wouldn't be here.... Yocto is a kit, which means you need to build it yourself. Many accidents can happen, but you learn a lot. I'd like to share some of the things I learned along the way... Yocto is made by e-licktronic.com

[tr-bob]

Hey Misa, thanks for your blog! Can you tell me wich cable are used on the pictures(does the white and red are usefull?) where you explain how to the BD instrument during the building process ? Thanks your blog is great I consider buy a yocto kit but i've build an LXR and a shruthi only and the yocto seems harder, on the build and on the debbugging...

I'm sorry, but I don't understand the question about the cables, could you be more specific?

The explanation for testing instruments is here:

http://tr-bob.tumblr.com/post/82331595450/using-an-arduino-and-a-bunch-of-crocodile-cables

Don't worry too much about the build and the debugging. I think Yocto is not that difficult -- but you need patience and should know how to use the soldering iron. It *does* take about 40 hours to build (took me about 1 hour to sort and 1 hour to solder for each section -- I was very meticulous because I knew it would be a nightmare to debug otherwise...)

The reason I focus on the debugging and fault finding here is, because those are the areas you need help in, not because mistakes are so common...;)

[tr-bob]

Hello, thank you for sharing this knowledge. Would you consider building it for someone else ?thank you for feedback

I would consider, since it was a fun build. But I'm pressed for time, there are probably others who could do it for you though. If you send me your e-mail we can see if maybe it is possible..

[miaoumusic]

LEGO Roland TR-808 by subclub on Flickr.

[tr-bob]

Anyone want to build a Yocto out of Lego?

[tr-bob]

Debugging and troubleshooting

Ok. Let's assume something went wrong. how do you go about debugging?

There are a few steps that are you should take before posting to the forum. This is taken from a DIY thread on muffwiggler.com:

"- 1st i try to think about it: WHAT does not work. - if nothing does work it might be power related, - if certain functions don't work i take a look at the schematics and check all related parts/values/wiring/solder joints.. i call this greenlining: take out the schematics and use a green pen for marking all connections/values you checked - any color will work, though ;-P - this might involve some analysis, since sometimes you have more than one error in a function block, or several errors across the module make it hard to localize the error."  (by fonik)

The general advice is: check for continuity first, BEFORE connecting power:

"A very valuable preliminary step that I learned from AndrewF is to use a meter across the power rails/pins (+ and -, + and 0, - and 0) to check for shorts on the board. If you get 0R reading, then there is a short somewhere. If you get some other (usually fairly high) value, then you should be good. This has saved me a TON of time looking for shorts manually. There could still be bridges or other defects, but it at least rules out the major ones." (j3rk)

and I have to absoluetey agree with him:

"After a while you get to a point where things just work right first time, most of the time. Don't worry, if it started happening to me, it can happen to you! However, rule one for me is: don't panic. It's fixable. Quite often the first order of business is to just put it down and go get a decent night of sleep. Chances are the first thing you look at in the morning will be the big stupid thing you forgot or did wrong. Usually wiring problems, although I can pretty much say that I've had every single error happen to me by now. My favorite was the mankato - I was painstaking about getting every little detail right, and then it didn't work at all. The next morning I saw that I had wired the output backwards - ground to tip, tip to ground, completely fubared. An easy mistake to make, easier to fix. My most common mistake is missing a pin when soldering in IC sockets - did that on my latest thing even." (sduck)

pre55ure suggests:

"1. check to make sure all components are correct and soldered properly 2. look for solder bridges/bad connections 3. check ic sockets for proper power 4. replace ic's 5. ???"

while andrewF adds:

"re: #4 replace ic's barring some power supply disaster, it is very rarely the chips. tho it is tempting to swap them out, better to exhaust all other possibilities 1st. Chips are not really that fragile, most can take a fair bit of punishment before shitting themselves."

Then Ray of MFOS has a great read on the subject:

http://www.musicfromouterspace.com/analogsynth_new/ELECTRONICS/troubleshooting.html

[tr-bob]

If you break one of the transistors (like I did...) don't despair. Just search for the part name in your favorite electronic retailer's online shop and order them. E-licktronic posted the links to a bunch of shops that carry the 2SC945 here:

www.e-licktronic.com/forum/viewtopic.php?f=16&t=218#p1195

http://radio-media-system.com/2SC945 http://www.mixelec.fr/article-87616-transistors-npn-traversants-2sc945.html http://www.cibi-normandie.fr/depannage-cibi/126-2sc945-p-nec-lot-de-5-pieces.html http://www.gotronic.fr/art-transistor-2sc945-1903.htm http://www.taydaelectronics.com/2sc945-c945-bipolar-transistors-npn-50v-0-15a.html http://www.siliconray.com/components/discrete-component/transistors/2sc945-to-92-npn-transistor.html http://www.elettronicashop.it/2sc945-c945-transistor-si-n-50v-0.1a-250mc-70C65.phtm http://www.silverdog.co.uk/shop/index.php?route=product/product&product_id=58 http://www.smallbearelec.com/servlet/Detail?no=1494

reichelt.de (I got my replacements from them. They have a comprehensive catalog, but a 10 EUR minimum order policy.)

[tr-bob]

At one point I realized that I had inadvertedly put in the wrong capacitors in the first step ("Power"). I assumed that everything in that bag was the same values... don't assume. Look at the components and measure everything you can... a few hours more during building will save you a lot of hours finding the wrong parts.

so I made this list and checked off the different caps to find the 0.47nF/50V ones...

I actually managed to put in 6 of the wrong ones....

[tr-bob]

using an Arduino and a bunch of crocodile cables, you can test the yocto even before you finished the seqencer.

Use this bit of code for the triggering:

http://www.e-licktronic.com/forum/viewtopic.php?f=16&t=179#p701

you will have an example in the patch points in the print out above.

this works for all instruments. attach the appropriate cables to the three components (resistors) that have "BD" (for the bassdrum), "TRIG" and "BD_OUT" written next to them on the circuit diagram.

Use the appropriate abbreviations for the other instruments and you can test them all.

[tr-bob]

Time for the faceplate. E-Licktronic make a (very wise) point stating that you only have one try for the faceplate sticker, saying that the glue is very strong. So how to align it with the top of the case?

I'm sure there are other options but I went a very low-tech way:

- take the long screws need for the enclosure

- stick them through the holes in the sticker

- lay the sticker down on the printed side and remove the protective film from the glue

- use the screws as guides and slowly "drop" the top of the case down onto the sticker.

this worked rather well for me. hope this helps.

[tr-bob]

It was in this state when I first tried out the Yocto (I added the other pots (tempo, instrument select and pattern) first). I was actually quite suprised to hear that there were only three issues:

- the high tom was triggered on every 16th beat

- the handclap did not play at all

- the cowbell sounded more like the horn of a car honking, not an 808

1&2 were fried transistors (that set me back about 1 week...), 3 required downloading "Scope", a (free demo) oscilloscope software for the Mac, that helped me to tune the Oscillators correctly.

[tr-bob]

The finished PCBs. sorry for the bad picture. I was in a rush to get things done, by now (4th week into the build)

[tr-bob]

Master section.

[tr-bob]

Hihats -- another very crowded section. but then, it's sort of like two instruments, too..

[tr-bob]

The Cymbal section. Not the two trimpots. These are (among other things) used to tune the oscillators of the cowbell, even though they are part of the Cymbal section.

[tr-bob]

the cowbell section. Take note that in some of the sections, components belong to the instrument that are not inside the dotted line. If you look at the circuit diagrams, you'll see that the handclap uses an opamp that is actually located in the rimshot section (U19).

Make sure you understand how to tune the cowbell. (it may require replacing some resistors. E-Licktronic actually provides some replacement values in the kit. This is due to the fact that the components are 5% tolerance rated. these 5% can add up to a different resistance than we want, thus it's impossible to get the correct timing in the two trimpots of the cowbell section.

[tr-bob]

The handclap section really is quite crowded. This was when I downloaded the EAGLE software (for PCB layouting -- free demo that lets you see, but not edit circuits) that lets you search for locations of components on the PCB. It saved a lot of time.

Nontheless I made another mistake here: I fried a transistor while building it. Q28 died (but I didn't notice until much later).

Vincent later walked me through a few steps of testing and he suggested that I replace Q28 and Q29 - that solved my problem immediately:

http://www.e-licktronic.com/forum/viewtopic.php?f=16&t=212

If you need to test a transistor, you can use the diode setting on your multimeter and follow these instructions:

http://www.stickycarpet.com/pinx/test.html

(the page is... a bit old-school. But the info there did the trick for me...

[tr-bob]

The rimshot section.

[tr-bob]

Someone wrote in a forum that his friend was bored by the built because it was so repetitive. Maybe it is, but I found the way of building instrument by instrument much safer.

You sort the components for each instrument and build them one by one. On the forum at e-licktronic.com, Vincent posted an arduino program that lets you trigger individual instruments of the Yocto before you finished the sequencer -- something that wouldn't be possible otherwise.