Sometime ago i bought Roland’s first ever synthesizer, for about a quarter of what it goes for these days-it was in dire condition, mind you. The control panel rusty and battered, the silkscreen on a couple of spots barely readable.
I always believed mint condition items belong to museums, not being fit for use, abuse and misuse.. i feel the same way about vinyl records-people who wrap them in polypropylene covers from day one and treat them as if they’re going to break anyday soon.. good grief
I must say that although i truly love the instrument- i also fit the Kenton cv/gate control board a year ago, i rarely ever used it.
The other day i took it out for a spin and the tuning was way off, it was drifting. It wouldnt even span an octave-it was that bad.
Time to recap, i thought, and pulled out the Elnas, the Nichicons and the soldering iron-i figured i’d give a refresh to the power filtering section, part of what the service notes call the “Pulse Sheet Assembly”..
Just a note: although the unit was in working condition, albeit out of tune, most of the 1uF caps on this board, were off their nominal capacitance-the 2.2 uF cap measuring a whooping 8.5 uF! Of the big 1000 uF caps, two were measuring 1200something uF, whereas the other two were still closer to the 1000 mark-and they all showed low ESR (40+ year old caps!). The three tantalum capacitors on this board were still working great, their value as per specs.
I fired the synth after recapping this board-the sound was a bit more definite, but the tuning was still off.
I decided to check the VCO board, pictured above. But, alas, no electrolytics there to substitute. I checked very carefully the board-and there it was, staring at me:
The diode+resistor combination to the upper far right of the board: the diode was broken in two!
The schematic calls for diode, 1S2473.. i checked a few diodes I had, and landed on a 1N4148 as a fitting substitute!
And.. yes now it IS tuned! The snipped diode was the issue!
Assorted pics of the wiring at the back of the oscillator board
Assorted pics of the actual boards.. might be useful to someone.
That good old recappin’ blues:
Since one of the boards was GLUED to its standoff, i had to solder some caps on top of the older ones.. now one of the caps had leads so short i thought it might be useful to remind myself where does each lead went (see pic w scribble).
And the odd freaky transistors that didnt have its legs cut off (and indeed they were perilously almost touching)
The FR8L can produce 13 drum sounds-and very crispy too, thats why i decided to modify it..
Circuitbenders.co.uk’s trigger module: wires aplenty, but this will allow me to trigger each drum sound from a midi to trigger highly liquid board, that has been assembled back in the day to control my fr3-a build/mod and brilliantly carried out by circuitbenders.co.uk (you can see it HERE and HERE TOO).
The trigger board for the fr8l can be ordered HERE but remember, stock is limited.
Please note a male/female hex spacer (m3 22mm) is needed to screw the trigger board to the existing hex nut.
I decided to put the trigger input jacks in an external box-lots of fun soldering all the tiny jacks!
Due to the nature of the machine it is best to reduce background noise as low as possible-and an external power supply may be a better power sourcethan the provided transformer since the filtering in the power supply section is basically nil.
I had to make a quick mod here so if you may, bear with the crudeness of these connections-i was also low on cables so pardon the lacking colour scheme..
Remove the transformer (WARNING: Dangerous voltages around this area)
First of all take a nice picture or two of where the transformer cables were originally.
The plastic thing where the red orange and black wires go is a diode bridge-check the schematic from the FR8L service manual, it has to be removed along with the transformer. We’ll reuse thosw wires so just cut them and leave them hanging for now.
Then when everything has been unscrewed and cables cut, make a bridge connection between the two pins of the on off switch at the tagboard end (pink cable).
Red and orange cables soldered to the positive side, grey cable connecting all black leftover cables to the negative side.
To attenuate noise from using a switching psu i put a choke in series with the positive pole, and a 2200uF 50v capacitor in parallel between + and – like this:
Remember the resistor between + at the psu and the orange cables (you can barely see it in the picture because i used some spare shrink tubing to prevent shorts).
The RE303 project is an amazing one-man effort to diy the Roland TB-303 Bassline to the extreme- starting with a cloned PCB of the original, and with a lively forum of rare parts being offered, recommended, sold and traded to make a 1:1 copy of the 303 (well, at least the circuitry).
Given the rarity and price tag associated with the original item, it should be of interest to anyone who’s a fan of Roland’s illustrious past.
I plunged into this project because i love acid house and its main voice, the TB303. I associate its sounds to the words “pearl”, “drop”, and the adjectives “wet” and “chirping”.
As anyone reading my blog already knows, i own a couple of x0xb0xes but neither of them had that “pearly” sound.
Cue the beginning of Phuture’s “Acid Trax”. The bassline rises from what seems to be white noise, a shash of the volume pot being slowly turned up.. the real TB303 must do magic stuff like that.
This is considered hardcore diy but really, it is hardcore part sourcing- you can choose how close to an original, you want it to be. I used a mixture of carbon and metal film resistors, whereas the original only sported the carbon variety.. most people go for the all-carbon build, just to give you an idea of the scene.
Ok, i bought the Space Cadet kit from dinsync.info and it arrived from Sweden in a low profile box, the pcbs wrapped in egyptian hyeroglyphics printed paper, very trippy. Also included are a couple of rare transistors, the pots, a Sumida coil, the bare rare basics.
-first of all i ventured out to buy knobs, buttons: syntaur.com, ebay
-rare transistors: the forum, more ebay action after a fake parts scare brewing through the forum with parts being measured, pictured and compared.
On the RE303 forum, there is a link to a Mouser cart with all the non rare stuff, but since my local retailer has got quite a good selection of vintage stock (1980’s), i decided to shop local and save on Mouser’s over inflated shipping and handling costs.
-Enclosure: on the forum it is offered in metal sheet, with fully customable graphics, or the “official metal case” with dinsync.info and RE303 logos, the mandatory plastic puzzle like cad template is also present..
This guide adds just a few tips to the already thorough building manual-stuff that has been replied on the forum or that i found out myself (not a lot).
If it’s not there, it should be here!
To build this i used a 35w cheapo soldering iron, just keep the point clean at all times, non rohs-approved solder, a cheap chinese diy oscilloscope (i bought it prebuilt, or as the ebay buy it now listing said, pre-“welded”), my Atlas Peak transistor tester, a simple DMM. I measured all the parts before soldering them to the board. I socketed all the IC spots.
Using the official enclosure?
to the switches pcb first of all- make sure you dont cut the ground line!
First of all you must install all the wire jumper. Tedious as HELL and you are going to lose your sight. There are two-three size jumpers. Quick tips using a typical cheapo ikea toolbox pincer for the most common sized jumpers:
Power supply section notes: use a nice and heavy switching (aka regulated) power supply/ ac dc transformer, centre negative. That way you wont burn yourself if you happen to touch the power transistor (it happened to me!).
Before you do anything, take a picture of the unpopulated pcb and print it. This will serve you as a guide to track down the position of so and so components, orientation of diodes and electrolytic caps, etc anything that once built, will not be easily readable-and you are going to need it once the built is over and you are going to need calibrating or (hopefully not) troubleshooting.
Build the power section after fitting the preliminary parts and all those jumpers (they are a lot and if you have an issue locating some of them, either look for some hi res pics @ the forum or, just leave it and you will find them as you go).
Some people like to put coloured tubing to the jumpers to add a nice lively effect to the build, i chose not to but it really is a nice idea. The trending colour is yellow as of April, 2017. 😊
Follow the official guide closely to measure and make sure the voltages are correct.. if you are having issues getting the magic 5.333v at TP5, you will have to “play” with R174, aka sticking a 4k7 resistor in parallel with it to lower its resistance. I soldered the 4k7 at the other side of the pcb. That gave me more play to dial the required voltage using the trimmer.
Build the VCO..
I have a 500R PTC tempco, as per original, but it did not fit the pcb with the components populated-i soldered it at the back of the pcb, shrink-tubed.
Make sure you have a few different brands’ 4066BE in case your final build sounds wobbly on slides and accented notes.
Here’s where that elusive D25 goes..
The pads in this section are very close.. if you check the schematic, you wouldnt worry too much about it, some of them are connected! For these you will need a tighter tolerance, 0,1% resistors.
(Please note the original had carefully chosen 0,5% tolerance resistors in this spot).
Do not forget to mark the parts going into those sockets and the IC orientation..
I used, 1N914 diodes instead of 1N4148 there-dont ask me why I did, but they should be pretty much the same.
That 303 ‘squarish’ wave through my cheapo unmodded chinese oscilloscope..
To check the waveforms, use the outmost pin of the waveform switch (ground) and the middle pin (positive).
Build the filter.
If should need a reference of how the transistors are oriented in this section, there you go:
Please note how i socketed the trannies of the filter section, it might be interesting to swap them later with different ones (as it happened, the 303 had a few revisions and the filter section uses transistors as diodes, so you may actually hear a subtle variation of its sound caused by the different transistors used).
This is also where the trimmer TM3 is (you will come back to this later when it comes to tuning the 303 properly).
To check the resonance, use this pin (aka TP6) of the pot-the furthest to the right. When you solder this specific pot, make sure it is aligned with the others.. look at how the pots sit from the side before soldering its six terminals. The rightmost pin is TP6, one of the testing points of the 303. Where is TP6? There. Remember.
Build the envelope section
Space Cadet kit, ENV pot measures 1M ohms.
Build the VCA
Remember that the negative pole of the tantalum capacitor is marked on the pcb.
Remember Q31 is not marked on the silkscreen.
Please note the ‘1’ mark, on top of R125, that signals the appropriate BA662A (aka ic15) pin 1 alignment.
Make sure you solder the two trigger jacks before you fit cap C37 to give you an idea of the cap measure you should use if you are not following the mouser cart..
Remember: at any time, these cv and trig are OUTbound signals.
Once you have all the i/o jacks fitted, you will get your mind blown by listening to the sound of you RE303 for the first time upon testing your work so far accomplished.
If you cannot find where they are, R181 is the one needing a bit of tubing, R182 is the to the left of the DIN socket pads.
Solder the selector and time pots with the pins aligned to the pads holes-they must not surface the back of the pcb! Try to solder them as even as possible.
If you are using the Sonic Potions CPU (like i did), just remember to leave out the ics as per the CPU’s installation manual.
The CPU will have to be fitted to the proper sockets: check this pic.
Rare part: the DIN sync jack.. I found it locally, from my retailer!
I had to remove the two innermost pins (it’s a double switch) to fit the pcb pads.. here’s what it does: when you plug a din sync drum machine, the internal sequencer timing is turned off and the TB303 is synced to the master DIN.
Two pins must be clipped off..But it fits perfectly!
I like the idea that my RE303 is powered by Philips.. 🙂
Please remember, if you are using the RE-303 official case, you will have to solder the midi dins directly to the SP ic.. just rock the molex male back and forth until it breaks and.. Bob’s your uncle.
Please note how i had to bend the transistors-i subbed the original miniaturized transistors with 2sc1310 (310) for the 2SC2603 but the SA115 could not be substituted-i tried to but experienced crazy behaviour on the keyboard..some switches were not working, etc
The silkscreen shows only the emitter mark of the transistors in this section.
I used shrink tubing cut to measure instead of the 6mm high led holders.
Due to the space constraint dictated by the height of the CPU sockets, I soldered the HD2 wires to the top of the switches PCB.
The wires linking the two pcbs have been wrapped with paper scotch tape in a flat cables fashion.
Later i removed these and switched to very functional flat ribbon cable from TE Connectivity (part number FSN-23A-20 for 20 pins, i then cut them to the needed pin count).
Ages ago i bought my first Mode Machines x0xb0x from Touched by Sound in Germany. They were the first fully assembled x0xb0xes on sale here in Europe and hence they have been reviewed a few months later on Sound on Sound. They came with those horrible looking MC303 knobs, but the idea of having a fully operational, Bassline clone with onboard sequencer was embarassingly exciting. In 2017 all this has changed, since the advent of the RE303!
From the description given to me by TBS and the sticker on mine, they indicated that they were Made in Germany.
One year later Mode Machines came up with the x0xb0x mk2, this time “guaranteed” to have been made in Germany.
Would this second statement imply, mine was actually made somewhere else other than Germany, EU?!
Today i decided to pop my Mode Machines x0xb0x open and have a look inside.
The machine itself, sounds good but it loses more of the lower frequencies than it should as you turn the cutoff and resonance up, but it sits nicely in a mix because of this and it is quite squelchy.
Now on with the gutshots:
Dirt on the pcb, almost like corrosive traces of handling, etc
Components scattered on the board and soldered, clearly assembled as quickly as possible.
Grey looking solder joints. I dont know if rohs approved solder is supposed to look like this but it’s not shiny, they look almost like cold solder joints.
Rubycon electrolytic caps.. part of the standard kit i suppose..
More traces of handling.. dirt..
All in all, the only other example i can think of of a pcb that bears the same, corroding handling marks, grey solder joints and cowboy assembling like this, is my chinese made, battered components sporting, bog standard, cheap as hell, barely working, terrible looking digital oscilloscope. They even smell bad, the same way.
My personal feeling: my Mode Machines x0xb0x was really either made in China or made in Germany by hurried chinese workers in a very dark and unpleasant cabin.
BUT: it sports original 536 transistors, that give it a very impressive TB303 character!
Sometime later, i got my hands on a NY made, x0xb0x from x0xs0urce: a whole different story.
Rounder sound, red leds instead of purple ones, and check these gutshots..careful assembling and soldering, etc. a work of love-mind you it costed twice the price of the mode machines..
Welcoming greenie caps as per the original tb303..
But ouch! This has 945 transistors (Roland mass production’s transistor of choice in those days)- it doesnt sound as wild as the Mode Machines!!
I do not think it is a difficult nor long build – i spent a couple of hours on every day off from work on it, for about a month.
The excitement of being able to own an 808 drove me, and gave me the needed focus and patience boost.
When building the Yocto, it is very important to measure every component before soldering it.
I decided to buy the resistors needed each time I was going to start a new section. This relieved me from measuring hundreds of resistors in one tiring session, putting them in order all at once, etc.
I bought a paper note book on which I would position the components, writing down their value and taping them, as I prepared for each part of the build. This helped me double check them before and while soldering them to the boards.
I decided to socket all the IC’s and the noise section transistor.
The germanium diodes provided in the half kit are rare, treat them with care. I cut the curvy terminals to have a straight lead as per this picture.
Check the pictures I am posting here to note certain ic’s position.
I made the mistake of putting all the pots at the end, do not do it, it is a mess. Just follow the build guide-do it as recommended, at the end of each section.
Remove the encoders’ tabs before you solder them in!
Please note that you do not have to cut the lead cables at the end of the build (i did it!), what Vincent meant in the last paragraph of the build guide is, you can make them shorter.
I had some issues with the flat cables, aka they broke, so i socketed them too. It is advisable to have a suitable enclosure ready before you get to link the two pcbs with flat cable, otherwise having the boards moving around will cause them to break. I would recommend you to buy this brand and sku: TE Connectivity-fsn-3a-10-3″ ribbon cable. They are the best. I socketed the connection point as per picture here, and i just slid the ribbon cable in the sockets-it works great.
Usually the boards sit a bit shallow in the enclosures, do not use led covers and cut LED leads so that mounted, they rise about the height of the sequencer’s coloured buttons.
Use 5mm spacers to lift the board up and have it sit properly, the keys will stick out properly through the holes.. i would suggest you buy a set of various spacers and screws etc that can be found on Am*zon, they come in their little handy boxes and experimenting with those will allow you to mount your precious yocto properly inside the enclosure.
More on that further down..
(see pic at the top of the post)
A few more tips to build the yocto, not a mod guide by any means, more like a ‘watch out for’ list, for instance where to look if you would like to change the value of some resistors to change the tuning of the instruments.. and other useful things to know as you go along.
A lot of these ideas are to be found in the yocto forum, but here is whatever I found essential to complete the build without headaches.
For a more in depth mods’ list, google dsl-man yocto.
Side note: please take note of these mods that allowed me to fine tune my build-i am not implying that these will be needed for your build, but keep these in mind:
Hats noise filter: for R58 use a 1K trimmer, multiturn
Cymbal noise filter: R56, use a 1K trimmer, multiturn
Cymbal decay: R93, use a 470K trimmer
Clave filter: R322, use a 20K trimmer
Clave decay: R313, use a 470K trimmer
SD noise filter: R202, use a 50K trimmer
TM1 and TM2 better adjustment range (Cowbell): at R44 put a 100K (or 56K if needed, see below the cymbal section) resistor, R45 put a 68K.
I put them on a veroboard or two, see at the bottom of the guide..
Also make sure you have many SC828 transistors to choose from for the noise generator!
THE NOISE SECTION
As opposed to the building guide, a more effective functionality of the noise generator can be achieved with this mod, as per the official Roland service manual (page 15):
R 129 use a jumper instead of the resistor listed
R 131 100k
R 127 10uF electrolytic: see this pic for correct orientation (positive side left)
R 130 22pF in parallel with resistor 130 (it means on top of the resistor, using the same soldering points – check the pic, i soldered it on the other side of the board)
I socketed Q35 as it is a very substantial part of the noise generator. Remember that for the noise section to work properly, 2SC828 transistor’s hfe must measure more or equal to 300.
NOS and new production 2SC828 values are all over the place, but ultimately you will realize most of them have a hfe thats lower than needed. Buy different sets from different sellers and take your time to measure them. Get your PEAK transistor tester out and measure them.
It can be time consuming, that’s the reason why Roland had them selected by the producer.. when stock finished, 808 production ceased-sometimes a 2SC945 was used as noise transistor. 2SC828‘s noise is grainy, as opposed to other transistors. There’s this mystique surrounding the selected transistors used by Roland, the same procedure has been used for the TR606 and CR8000 noise transistor-they were selected and are easy to spot if you would see a gutshot of said machines because the transistors have a white painted top. But remember: they are nothing special-they are just transistors whose hfe fall into range with the noise circuit. Dig into them and you will find one or two that will have the right specs.
Hfe lower than 300 will result in duller sounding, shorter decay, drier snare.
C 27 1n2 for 1ms pulse, needed for an effective accent
R 165 tuning resistor
R 234 47k (positioned in the Low Tom section)
R 188 check its position carefully
R 195 tuning resistor 1
R 196 tuning resistor 2
R 202 noise filter resistor
R 231 to lower pitch, use a 4k7 resistor (or increase value to lower pitch)
R 257 tuning resistor
R 284 tuning resistor
R 312 tuning resistor
R 315 tuning resistor
R 334 and
R 373 are part of the Hand Clap circuit, although they are to be found here
R 342 and
C 137 may have a solder bridge, it is ok
Do not rush to solder the BA6110 ic, it is better to socket it and add it at a later time, please check the picture here to have it positioned correctly.
R 63 decay resistor 1
R 65 decay resistor 2
The sound of this trademark instrument will be tuned once you get to the cymbal section, also please note the resistor values as pointed further up on the post.
Look at this section before trying to find the position of the components. It is L shaped.
R 56 noise filter variable resistor 1
R 58 noise filter variable resistor 2 (this is in common with the HiHat)
C 6 and
C 42 and
C 44 and
C 46 I did not have any 22nF caps in my stash so I used, 27nF instead.
This is the only section where it is mandatory to have a scope at hand-to tune the cowbell sound, using the two trimpots TM1 and TM2.
I used a Hantek 6022BE computer based USB scope.
Use one channel-probe on R44* resistor like this:
And ground crocodile on the above pot post like this:
Above: rotating slowly the trimpot, the values you want to see are 1.86mS, 526-540Hz and below, this wave:
If your trimpot cant get within range, change R44*. I had to lower its value to 100K first, but 56K finally got me in the range!
Time to probe TM2, like in the picture here, always grounding the nearest pot post too:
And the values you want to see, rotating carefully the variable resistor are: 1.25 mS, 800Hz:
And thats’s your cowbell sorted!
INPUT OUTPUT BOARD
Please note the position of IC4 on the i/o board..
IC4 is a optocoupler, 6N138 and it controls incoming midi signals, so if your yocto 808 has got any issue with midi like it will not sincronize to midi in, change this IC, maybe it would be better to go for a beige original:
Before you put the keys in, make sure your enclosure will let them stick out properly (as stated before, they sit a bit shallow), and use spacers the right height to suit your eclosure.. As described here..
Before you put it in the enclosure
Prep the enclosure by screwing the spacers in the front panel- i used 5mm spacers but 10mm spacers’ screws (aka the ones that came with the mouser order) that go in for like 3/4 of the spacer’s lenght. Screw the top panel side all the way in through the spacer.
Please note there are two sides to the spacer, one is hollow and the other flat. You want to have the hollow part as receptacle to screw the pcb side in (aka at the back of the front panel) as much as you can (it is not much, a few mm’s but that will suffice to have the pcb steady in place). This means, flat side of the spacer on top.
Look at the picture:
Nuts of the two encoders will have to be placed on top of the front panel not below.
My Yocto fired properly first off.
I made all the trimmer’s adjustment upon finishing it.
I am very satisfied by the result. Vincent has been very helpful too, and the YOCTO forum is an invaluable resource.
Thanks Pawluk for the sturdy enclosure!
Also, if you feel inclined, i would suggest you add a little daughterboard to fine tune the noise generator, to allow for correct voicing of the snare, hats and cymbal (check out the relevant resistors above and swap them with trimmers)..
I arranged them on a small veroboard and i am very happy with the results!
Lately (2019-2020) an unofficial custom firmware boasting amazing features as found on the original 808, such as instrument TAP writing, prompting users to update the ATMEGA ic.
For people who are modern pc challenged like me, i made a quick guide that you can find at this link: