Welcome to D' Naab 136 's Roland TB-303 Bassline (and other synths) repair and mod page

Yes, I know: this page is a mess. But I prefer working on the electronics instead of this page. Only basic info and some pictures are available here.

Contact me?
steel.report [AT] bigfoot.com (replace the [AT] with you know what)

Now available: Juno-106 full vca/vcf (80017A clone) replacement
For more info: click here

Information: How to do memory expansion for the 303 & 606
Some people are complaining that too much people keep the mods for 303's and 606's a secret. Here is my response:

Now available: TS-303 Acid Screamer
clickie for biggie
Distortion effect, built like a tank, based on the infamous TS-808 but with a much improved design resulting in a dramatically reduced noise level, double the distortion and with the possibility to go from zero to max distortion seamlessly, but with respect to the sound of the original. Also new input and output stage, although especially built for the levels coming from the 303, capable of handling any input level and driving every amp. (Even better in driving multi-mega Ohm impedances of tube amps than the original because the output stage can sink current).
Here is how it sounds (1.5Meg MP3)
Price: 110

Now available: Korg MS-20 upgrade:
If you are the owner of a first edition MS-20 (with the korg35 hybrid IC filter) you probably have noticed it produces a lot of noise. I can modify the VCF's and VCA so it produces much less noise without altering the sound characteristics. So how do you know if you have a first edition MS-20? By listening: The first edition filter 'screams' much more and is much noisier. Not sure: remove the left side panel and look inside if there is no extra board on top of the main board you have a first edition. See pictures:
Original MS-20 without filter board
New MS-20 with filter board
Price for the upgrade: 75

Now available: TB-303 computer interface:

Well, it took a while longer than expected but finaly the computer interface is available.
-Save/Load patterns on your pc: No more writing down your patterns
-Edit patterns on your pc: No more problems with double keypresses, going through the whole pattern to edit one note,...
-Edit patterns while they are playing: No need to stop and restart your 303
-Move patterns from one location to another one: want to use patterns from different banks in one track: no need to write them down and reprogram them. Just swap them from location. This can be done while playing.
-Take over the internal sequencer: play things your 303 can't
-Completely protected against wrong connections/electro static discharges/over voltage
-Software compatible from dos upto windows millenium is in full devellopment. Saving/Loading memory is ready and the pattern editor too. Track mode is in devellopment. When ready it will serve as blueprint for an opensource project for the software compatible with higher operating systems.

How does it work?
The interface is basically a signal router that can redirect the signals between the memory chips and 303's internal cpu and the signals between the cpu and the analog section of the 303 to and from an external connector. This is all done in a pure hardware fashion (no programmable devices like gals/microcontrollers/cpu's whatsoever) in a way that there is zero extra delay on these signals so that the behaviour of your 303 is not affected in any way. You may ask yourself the question why no programmable devices? This was the first design prerequisite I made when I started this project for the following reasons:
1: They generate delays and thus affect the behaviour of the 303
2: programmable devices don't last: the cells that store the program decay over time and that is unacceptable because I want my interfaces to outlast the 303's in which they were built in.

How is it installed?
-The transformer (T1) that is used as oscillator coil to generate the cpu's clock signal is desoldered and replaced to the underside of the main board.
-The memory chips are removed from the 303's main board and soldered on the interface.
-From the place where the memory chips used to be 20 wires are soldered that come from the interface
-2 tracks between the cpu and the chipselect decoder (IC2) are cut and 4 wires from the interface are soldered on the open ends.
-a wire from the interface is soldered to the base of Q4
-8 wire bridges are removed , 16 wires from the interface are soldered.
-1 resistor is removed , 2 wires from the interface are soldered.
-2 extra supply wires are soldered to ground and backup.
-A rectangular space is cut from the 303's case and 2 3mm holes are drilled where the connector comes.

Is it available as a kit so that you can install it yourself?
No. It is simply too difficult to do and if something is done wrong you may kill the 303's cpu and this part is irreplaceable and destroying that is thus unacceptable. The only way to get it is to have it installed by me

Is it safe?
It is very safe: Protected against everything (wrong signals, bad connection , over and undervoltage , electrostatic discharge) and in the unlikely event that you do manage to destroy the protection cirquits the interface is so designed that the 303's cirquits remain unaffected.

how much?
185 euro's

A big thx to:
Mr. Gasmask from binary bassline records who is always crazy enough to provide me with numerous 303's on which I can perform my perverted modification lusts.

pictures click=big
Side view of the interface (DB-25 connector that connects to the printerport of a pc)
Connected for the first time after assembly was completed
Connected for the first time after assembly was complete
Inside view of the 303 with the interface installed.
Side view of the inteface PCB between the main and switch board

below are some pics of prototype in test phase (clickie for biggie)
Stand alone test, not connected to the tb-303: Communication between a pc and the memory chips is tested.
Partialy connected test:Communication between a pc and the analogue section is tested and checked if the computer interface is accepted by the 303 on the sequencing part.
Fully connected test: Everything is tested: cpu<->mem , mem<->pc , cpu<->analogue , analogue<->pc. 100% functional

Some mods, repairs and prices
Replacement of the tactile switches: 52
Potentiometer replacement: (1+N)*12 where N is the number of pots that have to be replaced except for the resonance pot which counts for 2 (it requires adaptation before the knobs fit on it). This price is only valid for pots that I have in stock
Led replacement (orange, yellow, green, true - green): 15
Led replacement (deep blue): 45
Led replacement (white, turquoise and other crazy colors): contact me and I'll see what I can do
Lithium Battery: 30
Computer interface: 185
For other things like CV-Gate-Filter in, FM-mod, oddball stuff like morphing between waveforms, saw tooth curve adjustment (from linear talud response to f(x^n) with n adjustable and f(log(x)) or f=(exp(x)) ) contact me. All this will be available in a full package in the far future but if you want something done contact me.
Your TB-303 does not do what it is supposed to do? Tell me what is wrong with it and I will probably be able to tell you what is wrong with it.
Midi: More info soon

Some info for people who want to send me their 303 for repairs or mods
I am located in Belgium, Europe so you can check how much it will cost you to send me your 303. Make sure you send it registered and preferably insured!
If I have to send back to you it will cost you:
Europe: 7.49 shipping + 4.34 registration + optional 18 insurance (for a value of 1000)
Rest of the world: 11.49 shipping + 4.34 registration + optional 18 insurance (for a value of 1000)

Now available: White led mod for your tb-303
Very nice but very expensive! About 80

I'm currently looking for a 303 with a dead CPU because I'm planning to make a substitute for it and I do not want to remove a good CPU from a 303 because it could get damaged by the heat of my soldering iron. So if you own a 303 with a dead CPU do not hesitate to contact me.
If you need your 303 to be repaired or modified in any way contact me on this email address: steel.report [AT] bigfoot.com (replace the [AT] with you know what) with your questions and I will reply a.s.a.p.. Include as many details as possible like what is wrong, what needs to be modified, where you are located (I'm located in Belgium, Europe) for shipment and so on...
Also note that I do repairs and mod's on various other electronic devices (synths, amps ,mixers,...) and also make custom devices on demand (any kind of electronic device, computer hardware, speakers,...)

The pictures click on the images for larger ones

Worst case scenario: you drop it, it falls on the volume or tempo knob: Broken PCB
Broken PCB
Fixed using 0.05mm gauge coil wire view 1
Fixed using 0.05mm gauge coil wire view 2
Fixed using 0.05mm gauge coil wire view 3

And I thought the above one was bad. Imagine this: You have the most perfect condition tb-303 you've ever seen (not a scratch on it) A friend of yours who claims to know something about electronics says he will modify it for you, ages later you get it back with about everything messed up inside that can be messed up (including broken PCB) and some knobs, battery gutter, battery lid and all screws missing. Good thing this guy met me so I could save this one that has been dormant for about 10 years now. Plus a few basic mods and blue leds. Property of Stanny Fransen aka G-Force
Mister Blue click here for hi-res
Mister Blue again click here for hi-res
Mister Blue and some friends click here for hi-res

Mr. Yellow and Mr. Green. Property of Dr. Fernando

Below some pictures on how to do a button replacement and led mod. Some people pointed out that they do a 'cleaner' job on the dust-guard than me because they use a pre-perforated piece of plastic and so it doesn't look as wrinkled as my piece of plastic bag. Well, I do this on purpose because of the following reason: If you use pre-perforated plastic there will always be some gaps between the plastic and the leds and buttons and dust can go through. I however make only tiny cuts in the plastic and these will stretch just enough so the leds and buttons can go through and then the plastic firmly wraps around them so it forms an air-tight sealing and no dust at all will be able to enter.


Removing of the switches and leds

Installation of the new switches and leds.

Inserting a piece of plastic to keep dust out of the switches

Replacing the buttons