Dynacord Percuter Cartridges

The Dynacord Percuter

A few years ago i was in a music shop and i saw this old drum machine being used to hold coffee cups, the owner let me have it for 20€ with absolutely no guarantee whatsoever that it would work, it was missing its power supply and Sound Cartridges it had coffee spilled on it and was full of dust. Several years later with the kind help of Stefan Huebner who scanned the service manual for me and Tim Vanderhoeven who sent me an original Dynacord Cartridge to dissect, I have cloned the Dynacord sound cartridges. Ersatz Steckmodul V2 is now available

ERSATZ STECKMODUL

Compatibility:

the Dynacord Sound Cartridges are Used in several Dynacord products:

  • Dynacord Percuter (based on a design by BME, along with the Boomer Eprom Burner and BigBrain Sequencer)

  • Dynacord Percuter S (Identical to the percuter, but it has an extra circuit board which adds individual pitch controls, the main pcb is the same)

  • Dynacord Boomer (Untested but Writing should work for V1, Writing/Erasing Should work with V2)

  • Dynacord Mini P (A very nice looking two channel version of the P20, like the P20 it was designed by Fast Forward Designs)

  • Dynacord P20 (the P20 has "use only Original Dynacord Cartridges" written on it, does Mr Dynacord hate me?)

My cartridges are 100% electrically identical to the original dynacord cartridges and will work in any machine that uses the Dynacord cartridges.

The V2 Ersatz Steckmodule:
all signals are labeled, a cutout allow them to be erased in a dynacord boomer

Ersatz Steckmodul? what the hell are you talking about? you pervert.

In the Service manual for the Dynacord Percuter the Cartridge is shown only as a module called "STECKMODUL" since i am making a replacement for it i decided to call it the ERSATZ STECKMODUL, which is apparently a bit suggestive in german, so i have been told, my german sucks.

Technical Details.

The Eproms in the Dynacord Cartridges hold mono 8bit unsigned PCM audio.
there is no configuration data, start or stop points, just PCM audio. you can just make them with audacity and export as raw audio then burn them onto chips. they just need to be the correct size.

just like the Original Dynacord Carts, there are 6 cuttable configuration strips on the PCB.

A. Clock Speed: select 12.5khz or 25khz sample playback.
B. Envelope 1: cut to decrease decay time.
C. Envelope 2: cut to decrease decay time a bit more.
D. Envelope 3: cut to decrease decay time even more
E. Filter1: cut to enable Lowpass filter.
F. Filter 2: cut to enable Deemphasis filter.

Adding dip switches or toggle switches is possible, but i didn't add them to the design because it would increase the costs and assembly time significantly. it would be nice if somebody would design a 3d printed plastic cover that had holes for 6 toggle switches. My 3d CAD skills suck.

The original Percuter Cartridges can contain either one or two 2764 eproms,offering either 8k or 16k of sample data.

V2 also supports a single 27c128 eprom holding 16k of sample data. you need to add a jumper wire from A13EDGE to A1326 and populate the eprom in the 026 pcb.

The two pcbs are held together with turned pin headers so you can open them up and change the eprom easily. the originals were soldered together and stuck shut with potting compound.


Here is an audacity template to help you make your own sounds for burning onto eproms

percuterRomaudacitytemplate.zip

All the signals are labeled so if you want to do anything weird, have fun!

jp1 and jp2 are connected by default but you might need to cut them to use 2x2764 eproms.

Module assembled with a single 64k eprom

The two pcbs are connected with turned pin header strips so you can easily open the module to change the eprom.

Buy Modules And PCBS

I read somewhere that only 2000 percuters were ever made, i don't know how true that is, and my cartridges are compatible with several other Dynacord machines, but still, i'm not expecting a Queue at the door for these things.

available now on reverb:
https://reverb.com/item/38566887-dynacord-percuter-new-custom-rom-cartridge

if you want more than one cart, contact me directly.
i will also provide PCB only for those who know what they are doing.
send me an email. they are definitely cheaper than buying used carts!

i can make Carts with original or custom sounds, I have the majority of the original sounds available, or i can put your own custom sounds on a cart.

The Original Modules Dissasembled

It took some patience to disassemble the original modules, the one i got from Tim was partialy filled with smelly red potting compound, but it was possible to remove it with hot air and a bit of patience. then i took a while to annotate them nicely before starting to copy them in my pcb design software.

My Percuter came without a power supply so i had to make one, this info from the service manual was handy.
Get in touch if you want a new Psu for your percuter. i can make them on request.

Service manual and User manual

Dynacord Percuter Service Manual annotated.pdf
Dynacord Percuter Manual (1984).pdf

The service manual has some of my notes in it, ignore them if they are wrong.