Replacement components for repairing fx pedals

I repaired a few stompboxes for a friend and thought it worth writing down and linking to some of the replacement components, to hopefully speed up other people’s repairs as it took me hours to source the correct ones!

So if you need replacement faders / slide potentiometers for an Electro Harmonix Micro Synth then you want 100k Linear (B) with 30mm of travel. Small Bear sell them here and they also sell the little white toppers. I believe these pots are also the correct size for the POG 2. I actually used these Bourns ones from Mouser as I was buying a load of components from them – they are the exact same footprint as the Alpha ones that Small Bear sell but annoyingly the shaft is slightly shorter. It looks like this:

Slightly shorter Bourns slider pots from Mouser

The first and third sliders from the left are the slightly shorter Bourns ones…

Also if you need to replace the Q switch on your Jam Pedals Delay Llama Supreme or the Gate / Osc switch on your Death by Audio Supersonic Fuzz Gun then you want a miniature SPDT ON-ON toggle switch – this one from Rapid fit perfectly for me.

Need to replace the fuse in a T-Rex Fuel Tank Chameleon? You need a 250V t315 mA slow blow 20mm fuse. T-Rex sell them here, I got them cheaper from Maplin here. You need a 2mm or 5/64″ hex / allen key to open those up.

The DC sockets on Voodoo Labs power supplies are prone to breaking. I replaced some on a Pedal Power 2 Plus using 2.1mm right angled 2A sockets from RS Components and they fit perfectly.

The correct DC connector for Korg MS20-m and Volcas (and I believe most Korg products, as it’s a Japanese standard) is EIAJ type 3, centre positive.

That’s all for now but I’ll update this page as and when I do more repairs and find out anything useful worth sharing.

Repairing a Casiotone MT-400V and disabling the automatic power off (APO)

The Casiotone MT-400V is a cool old keyboard, most notable for being the only Casio with an analogue filter. I believe it is the same as the Casio CT-410V, but smaller. I fixed up an old one and thought it’d be worth sharing some of my findings to speed up repairs for others in the future.

Like most Casio keyboards it’s not exactly a professional instrument, but the sounds on it are great so I thought it was worth repairing. I’ve used it a lot on recording projects (you can hear it on the tracks The Love We Stole and When You Break on the Bear’s Den album Islands for example). However, it’s a bit annoying for live use because after five minutes of not pressing a key it automatically turns itself off. This can result in a nice loud bang through the PA if you’ve forgotten to mute it with a tuner or volume pedal. You can disable this quite easily by connecting two pins with a diode. If that’s what you’re after you can skip to the bottom of this page.

Inside the Casiotone MT-400V

Inside the Casiotone MT-400V – click to enlarge

If you take out a few screws and take the back off, this is what you’ll see. Two large green printed circuit boards. The one on the left is labelled M485-MA1M (D) and this contains the chip labelled NEC D930G. The pins on this chip control most of the functions, including disabling the APO. It’s an 80 pin chip, the bottom left corner has a dot on it and a number 1 printed on the board below. Pins 1-24 are along the bottom, 25-40 going up the right hand side, 41-64 going across from the top right corner to the top left corner and 65-80 going down from the top right corner back to the bottom left. I found it useful to draw a square with those eight numbers on when working on the keyboard so I could quickly check the number of the corner I was counting from when finding specific pins.

Click to enlarge

Across the top you can see two sets of wires which connect this PCB to the keyboard and to the front panel PCB. We need to connect certain pins on the main chip to activate certain functions, but because the pins are so tiny it’s much easier to connect these points to each other. These points are all connected to the pins we need.

The one on the left has 15 wires and has a number 15 on the first one on the left. So numbered from left to right, 15 down to 1, here is which pin on the chip each of those wires is connected to:

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
60 59 58 57 56 55 54 53 46 47 48 49 50 51 52

And the one on the right has 23 wires, I only found the pins I needed for the main functions, but the table below shows where those pins can be found on this one, again descending from left to right:

23 22 9 8 7 6 5 4 3 2 1
71 70 61 44 45

This table shows which pins to connect to which in order to achieve certain functions, some of which are ‘easter eggs’ that aren’t available unless you add modifications. It is adapted from the very useful TableHooters site. L followed by a number means the point on the left hand set of wires at the top of the large PCB, R followed by a number means the point on the right hand set of wires at the top of the large PCB:

 

51
50
49
48
47
46 
45
44
 
CPU pin
in L2
in L3
in L4
in L5
in L6
in L7
in R4
in R5
in / out
 
o
C1
o
C#1
o
D1
o
D#1
o
E1
o
F1
 
 
out L1
52
o
F#1
o
G1
o
G#1
o
A1
o
A#1
o
B1
 APO disable
C.
memory
mode
out L8
53
o
C2
o
C#2
o
D2
o
D#2
o
E2
o
F2
C.
casio
C.
fingered
out L9
54
o
F#2
o
G2
o
G#2
o
A2
o
A#2
o
B2
 C.
manual bass
 C.
arpeggio on
out L10
55
o
C3
o
C#3
o
D3
o
D#3
o
E3
o
F3
 
 
out L11
56
o
F#3
o
G3
o
G#3
o
A3
o
A#3
o
B3
 
key hold
out L12
57
o
C4
o
C#4
o
D4
o
D#4
o
E4
o
F4
 C.
memory
octave down
out L13
58
o
F#4
o
G4
o
G#4
o
A4
o
A#4
o
B4
transpose
on
transpose
set
out L14
59
o
C5
R.
synchro
R.
start/stop
R.
fill-in
O.
envelope 1
O.
envelope 2
O.
select
 R.
select
out L15
60
O.
pipe organ
O.
flute
O.
trumpet
O.
oboe
O.
violin
O.
bank switch
 
 
out R6
61
C.
bass 2
C.
bass 3
C.
chord 2
C.
chord 3
O.
sustain
O.
vibrato
O.
delayed
vibrato
O.
reverb.
out R8
71
R.
rock
R.
pops
R.
disco
R.
16 beat
R.
swing
 R.
latin swing
C.
arpeggio 2
C.
arpeggio 3
out R7
70

I’ve kept the TableHooters key –

“o”
 = keyboard key
underlined
 = function needs locking switch (i.e. stays active only so long the switch is closed)
R.
 = rhythm
C.
 = chord
O.
 = orchestra (main voice sound)
orange
background
 = easteregg (unconnected feature)

 

Some of the pins are inputs and some are outputs, so it’s important that you connect them using a diode. I used a 4148 diode. So to disable the APO we need to connect pin 53 to 45, which is out of L8 and into R4. The functions are activated on low, so he end of the diode with the black strip (the cathode) needs to be connected to pin 53 / point L8 and the other end (the anode) needs to be connected to pin 45 / point R4.

Because one of these points is on the left set of wires and the other is on the right they are quite far apart. I followed the traces and found points closer together that are connected to the same places. I checked for continuity with a multimeter. You can see the two points below – the connection disabling the APO is the top yellow wire. Ignore the five wires below, they are bridging a small break in the circuit board. And please ignore the poor soldering! I just wanted to get the thing working and then re-did it neatly later.

FullSizeRender (2)

Click to enlarge

 

So basically if you found this page just looking for how to disable the automatic power off “feature” on the Casiotone MT-400V, zoom in on the image above to see the two points you need to connect via a diode. Make sure you have the diode the right way round – though if you don’t, don’t worry too much, you’ll just notice that when you play the second or third octave of the keyboard you get extra notes. Desolder, turn the diode around, resolder!

UPDATE: Benoit Lachaise got in touch with me and confirmed this mod also works on the Casiotone MT-100 which uses the same D930G chip. He sent these photos to show the points he connected. Thanks Benoit!

Click to enlarge

Click to enlarge

How to use a Yamaha DD-5 to trigger a Korg Volca Beats

There are lots of old Yamaha DD-5 drum machines available very cheaply. I just had a quick look on eBay and there are four of five all for around £20-30. We actually got this one for free as my girlfriend works in a music shop, someone tried to sell it to them but since it has no resale value they didn’t purchase it. At the end of a fruitless day trying to sell it to other music shops, he came back and gave it to them because it wasn’t even worth him carrying it home!

They’re essentially cheap toys. The sounds are bad but they do have some retro charm. The potentially useful thing about them is that they do have a midi output, which made me wonder if I could use it as a set of midi drum pads to trigger a decent sounding drum machine such as the Korg Volca Beats.

By default the pads send the notes A1, E2, A2 and D#3 which is not much use. It is possible to change these notes (read how in the manual here) but it’s a bit fiddly since there is no screen. This was the first thing I tried and I got it working, however I was disappointed to find that when you turn the DD5 off and on again all these changes are lost, so it’s a bit of a waste of time.

So the next obvious thing to try is to remap the midi notes it sends using Logic. This way when the DD5 sends A1, I can convert it to C1 so it triggers the kick sound on the Volca.

Instructions on how to do this are below, or if you prefer you can just download my working Logic Project file here and play around with it.

Obviously first you need to connect the MIDI OUT of the DD5 to the midi input of your soundcard/interface and the MIDI IN of the Volca to the output.

First step was to check/set the midi channel on the DD-5 which is not too complicated. Hold down PAD ASSIGN and press TEMPO UP/DOWN to change it or press TEMPO UP and DOWN at the same time to set it to 1. (Since there’s no screen I use Midi Monitor to check what’s going on). I set it to 1 for simplicity. Then I set the Korg Volca Beats to receive on channel 1 too – hold down MEMORY while the Volca is turned off and then turn it on and you will see the channel displayed on the screen. Select channel 1 by pressing Kick then press play and record at the same time to save.

Then in Logic create a new Software Instrument track and choose ‘External Instrument’ as the plugin. (Important: dont create an External Instrument track as you can’t use MIDI FX such as ChordTrig on them.) For MIDI Destination select your soundcard, for MIDI channel select 1 and for input select 1. Then on the track between the External Instrument plugin and the EQ you’ll see ‘MIDI FX’. Click this and choose ChordTrig. Select Multi, double click Clear to get rid of any default mapping. Then Click learn. Now for each note from the DD-5 (A1, E2, A2 and D#3) you need to select it on the top keyboard then choose a note to map it to on the lower keyboard. To map them to the Korg Volca Beats Kick, Handclap, High Tom and Closed Hats sounds I use A1>C1 , E2>D#1 , A2>D2 and D#3>F#1. Unclick learn and close ChordTrig. Now try hitting your DD5 – hopefully it’ll be triggering the Korg!

If you want to link the DD5 pads to other Volca sounds, here is a full list of the Korg Volca Beats midi notes and numbers:

KICK C1 36
SNARE D1 38
CLAP D#1 39
CLOSED HAT F#1 42
LO TOM G1 43
OPEN HAT A#1 46
CRASH C#2 49
HI TOM D2 50
AGOGO G3 67
CLAVES D#4 75

Of course you could use this method to trigger any synth or drum machine software instrument on Logic or any external synth or drum machine that receives midi.

If you use Reason rather than Logic, this blog shows you how to do the same thing.