Here are some modifications and maintenance tips. Please also see the notes on spare parts in Q9 of the FAQ at the main Devil Fish page.
Household dust, especially flakes of skin, get into the switch and contaminate the contacts, causing them to become unreliable. This can make the TB-303 completely impossible to program.
These instructions tell you how to obtain new switches, and install them with a dust guard to prolong their life in the inevitable presence of dust. These instructions are directly relevant to the TR-606 as well. The TR-808 uses a slightly different version of the switch – the SKHCAB. It is possible to make a plastic dust-guard for the TR-808 - it is just a strip of plastic between the buttons and the switches. This probably only partially protects the switches from dust, but it is worth doing. The thin plastic I specify below adds slightly to the resting height of the buttons, but that is OK.
Even if only a few of your switches are bouncing, I recommend
replacing
the lot and installing a dust guard. I in 2004 only one person with a
Devil Fish from 1993 or 1994 has
contacted me about bouncing switches, and one person with a Devil Fish
from 1996 has also had his switches replaced. Both were heavily
used machines. So it seems that the dust guard greatly prolongs
the life of the switches, but does not ensure that they last forever in
well used machines.
You can obtain them from Farnell Electronics www.farnell.com. The SKHCAA is order code 733-271 and the SKHCAB (for the TR-808 and JP-8) is 733-283.
Mouser also has SKHCAB - for the TR-808: www.mouser.com/search/refine.aspx?Ntt=688-SKHCAB.
You will need 24 SKHCAA switches to replace those in the TB-303,
but
they are relatively cheap, especially when purchased by the hundred.
These
switches are not labelled SKHCAA, but have black buttons and bodies and
a 130
gram operating force. A similar shaped switch (SKHCAC) has a dark grey
button
and a 260 gram force. You can use these if you like - they are harder
to
press, but not too hard.
De-soldering the old switches is pretty straightforward. Take them
off
with their buttons still attached. I use a Weller vacuum de-soldering
station.
A second alternative is a standard soldering iron and a push-in,
press-to-release
solder sucker. The only problem with these is that the sucker may jump
forward
and damage tracks. A third alternative is to use solder-wick to soak up
the
excess solder.
Wash the buttons and the knobs with a toothbrush (an electric
toothbrush
is better, as it is for teeth!), in water with detergent. Rinse
thoroughly,
shake out water from the holes and allow to dry in warm air.
I make the dust guard from plastic sheet cut from a 3M overhead transparency protector. These consist of two sheets of clear plastic sheet 200 mm x 300 mm, bonded together, with two white cardboard fold-out strips. They are readily available from office supply shops and are labelled "3M Flip Frame (tm) Transparency Protector".
Cut a section of plastic sheet film 285 mm x 50 mm. Now you need to punch 6 to 6.5 mm (1/4") holes in it - one for each switch stem and one for each LED. I have my own template for doing them en-masse, but you will need to lay the plastic over the switches and LEDs and mark with a pen where the hole centres should be. The stems of the newly installed switches should make excellent references for your pen marks.
I align the rear of the sheet about 8mm beyond the top row of LEDs. Then use a hole punch from the office supply shop to punch the holes. (I use an acrylic template with 1mm holes to drill pilot holes in twenty or so sheets of plastic at a time. Then I staple four or so together and use a specially modified and very sharp 1/4" hand-operated hole punch. The punch has a filed down, pointed, piece of 1mm drill inserted in a hole I drilled in the centre of the punch. This helps me locate it correctly. The punch must be very sharp. I find it easier to use it quickly with four to six layers or plastic - if I only punch one, the plastic is so thin and flexible that it does not cut cleanly.
There also need to be four small holes for the Run/Stop and Tap
buttons.
I do these with a small leather hole punch.
Install all the buttons and carefully check that the dust guard plastic is not restricting their movement. By cutting the dust guard judiciously with a knife, any tensions can be alleviated.
Cut the dust guard to make way for the two screws which will hold the front panel PCB and battery guide to the top half of the case.
Check the alignment of the brown and orange wires on the left of the front panel. These should be pressed into the gap between C202 and S4. Test the operation of all switches and LEDs. Beware of broken wires or fractured solder joints in the cables leading to the front panel. Bend the white ribbon wires so they are not pressing against the top half of the case. (I routinely resolder both ends of the white ribbon wires between the main and front panel PCBs - these joints often fracture if this is not done.)
LEDs can sometimes fail to light because they have been hit physically in the past, weakening their solder joints - so waggle them to test this and re-solder them as required. Once I had a TB-303 with a LED which was internally corroded due to some liquid being poured on it in the past. The LED worked fine, but it had a resistance in the reverse direction which upset the switch scanning, causing a curious effect: random activation of button functions within a set of switches when any one of the switches is pressed.
See the notes below on general maintenance before closing the
machine
up and giving it a final test.
The ALPS website should have more up-to-date distributor
information: http://www.alps.com
If pure water gets into the machine, due to rain or some other source, just let it dry. If there is lots of water, pull it apart and mop it up with tissues before letting it dry in warm air. The 24 tact switches will not like being immersed in anything – but they may survive water. But how could they dry properly, since the actuator is closed against the retaining ring except when it is pressed?
If some other liquid - such as Bundy (Bundaberg Rum) and Coke -
gets
into a machine, open it up and wash it away with warm water, using a
toothbrush
and maybe just a little detergent. Then let it dry in warm
air.
Best replace the tact switches!
Update 28 April 2002: A USA-based person (with links to China and Asia) who requested I not put his name on this Web site has newly manufactured pots for the TB-303. He is known by his eBay auctions as ChipForBrains. He has requested that I make this address known for all people who want to order these parts: chipforbrains at technologytransplant dot com (Edit this to a proper email address - this obscuring is to help avoid spam address collection.) . His site is http://www.technologytransplant.com . Maybe "sales" at this address will work too - he has changed his email address in the past to avoid spam. (By the way, he now sells a complete replacement TB-303 switch board (via eBay, it seems): http://www.technologytransplant.us/repairdocs/TB-303/SwitchPCB/TB-303SequencerSwitchBoard.html . See his auctions here: http://cgi6.ebay.com/ws/eBayISAPI.dll?ViewSellersOtherItems&userid=chipforbrains&completed=0&sort=3&since=-1 )
In March 2006, the sets of 6 pots I received are good replacements, with a few caveats:
These pots are not made by ALPS, which is unsurprising, since I don't think ALPS has made them since the mid 1980s. The only problem is that the Resonance pots have a spline on their shaft which is significantly wider than the others, and many of the original TB-303 knobs to not fit it. However some do. There's no rhyme or reason about this - of 30 knobs in 5 machines, I found 15 which fitted. Those which did not fit would not fit at all. Those which did fit were close, but easy to slide on. See notes below on the 5mm longer shaft pots for modifying knobs to fit these wider shafts. I have been told that it is practical to remove the shaft and wiper from the Alps pot and install it in the new replacement pot. I am not sure if this report concerned single pots or the dual Resonance pot. This may be a good approach if the technician is up for pulling apart and reassembling pots.
- The mounting lugs are cadmium (I assume) plated. They need to be filed back to steel, at least on the outside, because it is impossible to solder to the plating.
- The replacement Resonance pot is labelled "50KB", which is what it should be (a dual 50k linear) but the taper (the relationship between rotation and resistance) is not linear. It is "logarithmic" at both the anti-clockwise and clockwise ends, while ordinary log pots ("A") are logarithmic at the anti-clockwise end. This means that most of the active musical range of the knob is compressed into a narrower rotational range of about 10 to 2 o'clock. The pots still have a complete range of resonance values - its just that they are compressed into the middle or the rotational range. I refer to this in the Devil Fish Release Notes: release.html#pots .
- The shaft of the Resonance pot is too large, as noted below. While it is possible to force some of the knobs onto it (TB-303 small knobs have two slightly different hole diameters and spline geometries), this is not suitable for the Devil Fish, since it is necessary to pull all the knobs (apart from Tempo) off with adhesive tape or some other means before dismantling the machine.
A complete set of 6 small "top" pots for the TB-303:
- 50K Linear - Tuning and Accent.
- Dual 50K (supposedly) Linear - Resonance.
- 50K Log - Cut Off and Env Mod.
- 1M Log - Decay.
It is impossible to say how long any new kind of pot will last. The ALPS pots, all things considered, have proven to be very reliable. There have been no obvious problems with the new pots from technologytranspant.com (except one replacement Resonance pot with an intermittent short between pins 5 and 6 due to wipers inside being bent and some pots from 2004 or so not having their contacts riveted properly).
The most common causes of failure of the original pots seem to be:
- The tracks being worn through by the outer rim of the internal rotating part pressing against it. In the new pots, and I think the ALPS ones, this outer rim was intended as a dust guard, and is not normally touching the tracks. However, if the shaft is pressed downwards or sideways, or perhaps if the central support point became worn, then this rim would rub against the tracks and ultimately wear through them.
- Problems with the riveted metal pin no-longer contacting the metallised carbon conductive resistance track. This is typically due to someone spraying oily substances in the machine. It can be corrected (with unknown reliability) by cleaning the whole area and pressing the rivet a little more closed, to maintain greater pressure between the two items. Probably, silver-loaded conductive epoxy resin would achieve the same result, but I am wary of how that would handle the heat of soldering - so perhaps it should be done once the pot is cleaned and re-soldered into the PCB.
No-one is producing TB-303 CPU chips, and it would be difficult to do since this kind of 4 bit CPU has not been made by NEC for many years. Someone suggested they could reverse engineer its behavior, program a modern CPU to perform the same functions, and then build that CPU onto a daughter-board so it could replace the CPU. If this is done, and if someone creates new PCBs, and finds various components such as the power supply transformer, the rotary switches, the waveform switch, the switched DIN socket and the marvellously reliable 6.5mm audio sockets, then it should be possible to make a TB-303 from all new parts. This stage of hot-rodding, to the point of being able to make a new machine without original parts, seems to be something which only happens to the most venerated items of hardware, such as a VW engine!
One project for creating a replacement CPU, with extra capabilities such as MIDI, is: http://ultra303.ultrafex.de/
The following was written before the abovementioned replacement pots became available. I am providing it here for reference, but suggest that it is much better to purchase those proper replacement pots. Replacing the TB-303's potentiometers - the small ones, not the tempo and volume
This is an updated version of what I wrote this for the Analogue Heaven mailing list on 19 January 2001. In that, I incorrectly stated that the Resonance pot was log. It is linear.See the notes at the end about reliability, and how Rob (see below) can apparently
repair worn out pots. He may also be able to get some pots manufactured by CTS: http://www.ctscorp.com/electro/ffpots.htm .TB-303 pots have not been obtainable from Roland for many years. They
are no longer produced by ALPS. (Maybe you can still get a tempo or
volume pot from ALPS or even Roland.)Finally, ALPS has a web site:
The best replacement I know of, is to get a Panasonic pot and adapt it.
The Panasonic site is labyrinthine . . . they are under "Passive and
Electromechanical Components"
http://www.panasonic.com/industrial_oem/electronic_components/electronic_components_home.htm
From there choose "Potentiometers and Encoders" and you can download a
.PDF file.The Panasonic and Digikey ( http://www.digikey.com ) part numbers are:
Dual 50K Log EVJ-Y10F03R54 P2G1503-ND
Dual 50K Lin EVJ-Y91F03B54 P2E9503-ND
The TB-303 pots are:
Tuning 50K Lin
Cut Off 50K Log
Resonance Dual 50K Lin
Env Mod 50K Log
Decay 1M Lin
Accent 50K Lin
Don't try the single versions of the Panasonic pots. The Dual has a wider base,
and so is closer to the mounting arrangement you want.The dual Panasonic pots have the same pinout as the original Alps
resonance pot, so you should be able to wire it up directly, though I
think the pins are slightly differently spaced.For the single pots, just use pins 3, 4 and 5 of the dual pot.
The Panasonic shafts are flatted rounds, not splines as in the Alps
pots. (I have scrutinized the Panasonic site, it it seems they don't do
spline shafts at all.) To use the TB-303 knob with the Panasonic pot,
you will need to very carefully file or gouge or whatever most of the
knob's splines so it will fit the shaft. I left 7 splines intact. You
will probably want to file the tip of the shaft down as well. A bit of
Blu-Tack will help hold the knob in place. (Alternatively, perhaps
filing the shaft into a square or triangle might make it fit the knob
snuggly.)The shaft is the right length.
The linear pot has a centre detent. (Digikey has no dual 50K pots in
this range without detent.) I got rid of this by opening the pot (bend
the four lugs at the rear) and filing away something. (My notes are not
exact, so I can't tell you what I did, but it would be obvious once you
open it up.)Also, I removed quite a bit of grease from the shaft bearing area to
make the pot easier to turn. I suggest this for all these Panasonic
pots - linear and log.If you get some log and linears of these dual pots, then this covers you
for all pots except the Decay pot - which is 1 Meg and so is outside the
range carried by Digikey.My best suggestion for the Decay pot is a smallish 9mm single 1 Meg Log
(Oops - I had written Lin!) . . . well, my suggestion was a 1 Meg Lin pot
by Alpha from Altronics in Western Australia: "R 1930" from
http://www.altronics.com.au (Beware this may hang Netscape - I
reported the problem.) but they don't have any log ones. If you can
get a 1 Meg Log one of these perhaps it can be adapted to use in a
TB-303, but this would make no sense if you can get pots mentioned
above.
This is the sort of work which should be done by a technician. If you
don't have a lot of soldering and electronic experience, then there is a
big risk that you will damage the machine. Since TB-303 are rare and
expensive beasts, I urge you to get the work done by someone who is
unlikely to make a mess of it.
The only decent replacements for the TB-303's small knobs I knew of are
from Rob at the following site. However, in August 2004, I could see nothing
there about knobs etc. - he seems to be concentrating on motor car engines.
These are in clear or opaque resin of any colour, with fillings such as multicoloured
metallic flakes (actually: "alien heads, smiley faces, silver glitter stars, glitter") and
even LEDs. Seriously trippy! He can also "chrome plate" the tops of them, and
make new knobs for any other machine - all he needs is a sample.In August 2002, I saw some of these knobs. The "chrome plating" looks like
aluminium and I am not convinced it would survive a lot of friction, but I did not try.
I fitted a set of translucent purple or mauve knobs to a purple AluCase Devil Fish
and they looked good. Rob supplies some reflective aluminised cardboard cut and
punched to go behind the knobs. These do not rotate - it was a single sheet to go
behind all the six small knobs. We did not fit it to this, but it is clear that the
reflective material would make the translucent knobs look quite a lot brighter.
Translucent knobs show the shaft and the hole in the knob for the shaft, so they
are quite a different thing from opaque knobs. Rob also sent some uncoloured,
light green and orange small TB-303 knobs, some "chrome plated" and they all
fitted the "Technologytransplant" Resonance pots, which, as mentioned above, have
a slightly larger spline diameter.
I think it would be good to make a modified knob which is 3 to 5mm higher, since
the TB-303 knobs are very low and hard to use.
Another alternative is Altronics grey hard rubbery knobs with
coloured plastic indicator lines. They are longer than the TB-303
pots, but they sit at the same height, so they extend further inside the
TB-303. If the TB-303 is a Devil Fish, then you should trim off the
bottom rim of plastic with a knife so it does not hit the rear panel
Devil Fish PCB. They are nice to grip! Its a pity they don't extend
any higher. You could probably pack them with something and make them a
mm or two higher, but then they may fall off.They are:
H 6020 Red H 6022 Blue H 6024 Grey
H 6026 Purple H 6028 Green H 6030 BlackThe Altronics site is http://www.altronics.com.au . Watch out, it may
crash Netscape - I have reported this problem.
These knobs don't look as good, I think, as the standard knobs but they
are much better to grip.The bases of these knobs are narrower than the TB-303s. One of the
benefits of the TB-303's knobs is that sideways forces are borne by the
knob against the top case, rather than bending the pot shaft. Such
bending whilst rotating can easily destroy the pot, because the standard
pots (and the new ones mentioned above) have a cylindrical rim of plastic
which takes such pressure and runs over the conductive tracks. This
can cut through the conductive tracks! (Rob, mentioned above, is able
to repair pots with such damage!)These new knobs do not fit like this, so please be careful not to move
the knob side-to-side because that will strain the pot and probably
cause premature failure.
NEVER SPRAY ANYTHING in POTS or SWITCHES unless you
really want to really foul up your equipment.Never glue knobs to pot shafts either! Use "Blu-Tack" or whatever the
The above is the absolute sum-total of my knowledge - so please don't
local species of "stick posters on wall with putty-like *stuff*" is
called in your locality.
ask for further instructions. Please do suggest better alternatives!
The same problem of broken solder joints occurs with the sync socket and may occur with the waveform switch.
A better approach is to use short lengths of thin insulated wire to link (with a fresh solder joint) that pin of the connector with the track it is supposed to connect to – at some distance from the solder joint between the track and the pin. This wire can go to the joint of another component, or to an area of the track with the solder resist scraped away. Make sure the wire link is 10 mm or so away from the pin so it is flexible enough to stand the pin moving without breaking itself, the track or the solder-joint to the track. I generally use 25 mm lengths of insulated Wire-Wrap wire to do this. This means that if future stresses cause another failure in the solder joint, then there will still be electrical connection via the wire from the solder on the pin itself to the track nearby.
The power socket sometimes needs replacing because it seems to
make
poor contact with the adaptor plug. These sockets are easy to get.
Sometimes
the trouble seems to be in the socket – where the centre pin is
"riveted"
to the lead to the PCB. Cleaning up and soldering over this joint area
works,
but may not last since flexing will fatigue the solder joint. Better to
install
a fresh socket.
Keep an eye out for loose nuts on the tempo and volume pots.
The negative spring connector can be a problem too – especially when it has been subject to corrosion from leaking batteries. Remove it from the machine, wash any corrosive materials and rust from it and file the end to expose fresh steel.
The wires to these connectors often fracture after several
assembly-reassembly
cycles, because the wire is impregnated with solder. Simply trim back
the
wires and re-solder them.
These instructions are given on the understanding that they will
be
carried out by someone with some electronic expertise. Don't do
them if
you are unsure of yourself and don't email me for support if you get
into
trouble. If you get into trouble doing these simple things then you
should
have recognised that you lacked even the most basic expertise.
To provide a lower limit to the range of frequencies, without
altering
the high limit, short out R47 - a 10K resistor just to the left of the
Env
Mod pot. Do this short with a small length of insulated wire on the
rear side
of the PCB.
To extend the range of the Env Mod pot to include zero envelope
modification,
then short out R61 (10K) which is located logically and physically to
the
anti-clockwise pin of the Env Mod pot.
This gives a worthwhile improvement in bass response. If you want
to
restore the original TB-303 sound, just do it externally with EQ.
Jarrod Trainque wrote:
> okay I'll rephrase for the original poster:
>
> How long can we expect to see tb303's around... given that not
> everyone takes ultimate care of their machines, one or two
303's
> probably crap out permanently each year... given that there is
a
> finite number of 303's in existence, how soon should we expect
to
see
> the effects of age?
There were supposedly 15,000 or so TB-303s made, of which most
were
sold.
I guess there are 10,000 or so in "circulation" now - of which
quite
a
few thousand are sitting in the closets of the singer-guitarists who
primarily bought them in 1982-84. They may have their
batteries
in
them, so the batteries will be rotting and probably making a mess of
the machine.
I have seen TB-303s which have been so heavily used in
techno/dance
that
the lettering, paint and plastic is worn away around the cut-off and
resonance knobs - but the machine is still working fine. The
pots
can
last an amazing time, but they can also fail without warning.
Pressing
on the knobs or sideways pressure will hasten their demise of the
pots,
since internally, some stress is taken by a circular piece of
plastic
which rides *on* the conductive track.
I have written to AH and on my site:
http://www.firstpr.com.au/rwi/dfish/303-mods.html
about replacing the pots.
The plastic cases can be pretty bad, but still functional.
The
ultimate
replacements are from Switzerland, personalised with your text,
colour
scheme and special requirements - with extreme beauty and precision,
from DJ, musician and CNC/CAD fiend Martin Rothlisberger:
At a pinch, you can use a TR-606 case - just swap over the metal
plate
around the tact switches.
The knobs and buttons are metal coated plastic and never wear
out.
The
small knobs can fall off, so I use a little "Blu-Tack" (for sticking
posters to walls) to keep them in place. ****Never**** glue
the
knobs
in place!!!!
The dangers to the machine include:
1 - Running it from an adaptor which puts out more than 9 volts
DC,
with the low load current - ~140 mA - of the
TB-303
/ Devil Fish.
A common problem is using a 12 volt adaptor
or
a "9 volt" adaptor
which is meant to put out 9 volts with a load of
500
mA. At a lower
current it will put out 10 or more volts.
Higher voltages burn out the regulator
transistor.
See my page
for how to replace it with a TIP30.
2 - The power adaptor socket can get ratty. This is easy
to
replace -
they are available everywhere, including Radio
Shack
/ Tandy.
3 - Leaving batteries inside the machine, where they leak.
This
can
make a mess of the battery contacts. The
spring
at the bottom is
difficult to replace - except, I guess, unless
you
rat one from
a TR-606 or some other device.
The greatest danger is that the battery
"acid"
(it may be alkali -
but whatever it is, it is corrosive) will affect
the
circuit
board and components. This can get
very
messy.
One nasty effect of a corrosive atmosphere is
the
corrosion of the
power and write-enable pins of the memory chips,
because
they
are at about 6 volts. They corrode from
the inside
and you may
have no continuity - but the memory sort of
works.
Beware! Only
one brand of memory chip is affected like this,
but
I can't
remember which. I have plenty of
spares
- but otherwise these
1k x 4 battery-backup static RAMs could be hard
to
get.
4 - Spraying anything, especially oily things, in the switches or
pots. This can be cleaned up when the
switches
are replaced. Oil
can make the pots fail - which is very serious.
Never spray anything in anything!
5 - Dropping something on the knobs and breaking the circuit board.
This can be repaired, but it is labour
intensive.
Always pack
the machine carefully so nothing can bang
against
it in transit.
6 - A CPU chip dying. This is pretty rare. There are
no
replacements.
It is a custom CPU chip which is unobtainable
and cannot
be copied
- unless someone wants to spend a few years on
programming
another
CPU to do the same job.
7 - The sync socket's solder joints breaking. This happens
all
the
time and is easy to fix.
8 - Likewise, the solder joints on the audio sockets.
Remarkably,
the audio sockets *never* fail in all my
experience.
They are
a marvel.
9 - The tempo and volume pots could fail and be hard to replace,
but
in general, they work fine.
The tact switches become intermittent due to dust - this makes
the
machine impossible to program. They can be replaced and I
always
install an internal flexible dust guard - which seems to make them
run
for a very long time.
There have been no failures of the magnificent little ALPS pots
in
the
Devil Fish controls.
The three position toggleswitches become less distinct in their
action
with a lot of use - but they still work. As far as I know,
they
have
only failed when something has dropped on them.
The 3.5 mm sockets in the Devil Fish are extremely robust, but
there
have been some perplexing intermittent failures of the CV-In socket
-
which causes it not to run properly from the internal
sequencer.
I have
tried to eliminate this problem. It can usually be fixed by
plugging
something in and out of the socket a few times.
See the end of the Devil Fish release notes for a few other minor
issues.
There will still be TB-303s running and being used after we are
all
dead
and gone - fewer than now, and most will be rather worn out - but
some
will appear from the closets of guitarists of the 1980s almost
untouched
for many decades to come. Those with AluCases may have their
cases
battered and faded with many years of work, but they will still be
robust and probably look all the more fantastic for their many
travels.
- Robin
Robin Whittle - First Principles and Real World Interfaces
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