This particular drum machine is a favourite of mine to bend, as its results are phenomenal! In this project I decided to utilise a patch bay, as it allows full use of the bends instead of permanently wired switches to certain points which limit the users control. Most of my projects use patch bays as you’ll notice, but that just personal preference. Once inside the machine, you’ll find its pretty sparse, which always helps in finding bend points, but all the safest bends and connections are made on two chips.I’ve decided to re-write this page to make it a bit clearer for everybody since i keep getting asked for schematics, which i don’t have, as I’ve not produced any, sorry.

:::DISCLAIMER:::

CIRCUIT BENDING CAN BE DANGEROUS. I ACCEPT NO RESPONSIBILITY FOR DAMAGE TO YOUR HEALTH OR YOUR MACHINES IF YOU ATTEMPT ANYTHING I OFFER BELOW.

DUE THE AGE OF MOST BENDABLE OBJECTS, THEY CAN SOMETIMES BE ON THEIR LAST LEGS AS IT IS, SO TINKERING WITH THEM IN THIS FASHION AND PROBING AREAS YOU SHOULDN’T CAN PERMANENTLY BEND THEM OR KILL THEM UNEXPECTEDLY, RESULTING IN A LOVELY RETRO PAPERWEIGHT. I OFFER NO GUARENTEES THAT WHAT WORKS FOR ME AND MY MACHINES WILL WORK PERFECTLY FOR YOURS.

YOU HAVE BEEN WARNED.

CAUTION: TAKE CARE HANDLING THE PCB EVEN WHEN NOT CONNECTED TO THE MAINS POWER SUPPLY, THERE ARE SOME LARGE CAPACITORS IN THERE THAT COULD/WILL HURT YOU! I AM NOT RESPONSIBLE FOR YOUR WELL BEING.

1) Take your HR-16 and flip it over. Take out all the screws. There should be 4 of them, a nice easy one to open. Put the screws somewhere safe, a bowl is handy.

Seperate the top and bottom cases. You’ll find that the top is connected by a few jumper wires. these have plugs on one end to make it easier to dismantle. just remember the polarity of the jumpers for when you reconnect it later, however if you need to test your bends first, its easier to leave them connected so you’ll still have button functions while testing.

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2) The PCB we want is located in the bottom half of the unit. Again, you need to remove the screws to access the underside of this PCB. You’ll notice that this contains all the chips, capacitors, jack sockets etc. It’ll look like this, but without the blue wires….

The top half has all the button and display PCB’s in it. Theres not much of interest in the top section unless you need to clean sticky buttons.

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3) Taking the bottom PCB, you need to locate the two horizontaly mounted IC’s (chips), everything else is vertically mounted. They are located right behind the TAPE IN/OUT and OUTPUT2 jack sockets and infront of a a square chip and a small battery. The chips have 32 pins each, count them if you have to make sure you got the right ones.

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4) The two chips seem to be idenctical in function for bending purposes. I have no idea why but they must contain the same data and perform the same functions, but this makes the machine even easier to bend, as you dont have to worry about soldering every pin on one chip. You can stagger them for ease across both chips.

Remove the PCB from the case. flip it over and find the 4 rows of pins from the two chips underneath.

Take you test cables, run a pattern in the drum machine, and start connecting 2 pins from either of the two chips together to create bend points. I’ve found there are very few combinations that will stall the machine, and i’ll try and dig out my notes on the ones that do. Play around and see what does what, you might like to take notes so you can groupcertain types of bend effects together later on. The more you understand the better.

Remember the points that you’d like to hard wire switches (or anything you like) to, or, if you are the control freak that i am, and love a bit of hard work, you can take them all for a patch bay.

The easiest option for bends like this is to use ribbon cable, i prefer rainbow cable as its easier to identify the strands than the standard grey and single red ribbon cable you get, however at the time i didnt have any so settled on single stranded wire.

Remember to prepare and tin the ends of the wire first, its much easier to solder this way. It’s a good idea to measure how much cable you need for one, stretching from where the final resting place of the PCB will be, and snaked through the inside of the machine to the point where the wire will be connected to the front panel, and cut identical lengths. Measure twice, cut once, its easier, and you’ll thank yourself one day….

CAUTION: ALWAYS DISCONNECT FROM THE MAINS POWER SUPPLY BEFORE SOLDERING ANYTHING!

I settled on a 28 way patchbay, mainly because this would fit my front panel design, so i needed 28 pins from the two chips to be soldered. The end result looked like this, notice the staggered pin soldering across the two chips. By this, I mean every second pin is soldered to a wire, and alternated on the second chip so we have all 28 different pins that we needed.You’ll notice a salmon coloured wire on the left photo. this was there already, and is a PCB revision, if yours doesn’t have it, its not going to be an issue for this project.

In this formation i end up with 14 pins on each chip, 7 on each side, being connected to as bend points.

Solder 3.5mm mono jack sockets (or banana sockets) to the end of each of the cables connected to the pins on the chips, as per below.

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5) Now we have to build the front panel. I went for a 28 way patchbay, with a switchable 3 or 6 way multi point bay, and 6 patch switches for on/off switching of the bends connected to the switch. These switches have indicator LED’s which arent needed, but I have an LED fetish, and their blue…

Take the top section of the case, and remove the flip up lid. Unfortunately i have not found a way of removing this with out breaking its hindge. the plastic is too rigid to bend far enough with out snaping. Remove the instruction lable on the inside. this is stuck down with some heavy duty adhesive, and rubbing alcohol might be needed to remove the sticky bits left behind…. I say “might” but this has always been the case for me.

I find the easiest way to plot out the holes is to draw them on graph paper first, then cut it out and lightly stick it to the inside with a minimal scoosh of spay mount. if you do it on the inside, it doesn’t matter so much about getting it off, but remember to invert your design. double check you get it right, as once you start drilling theres no going back!

My patchbay sockets, switches and LED’s are all mounted in a 15mm pitched grid, with a 10mm boarder from the edges of the case to allow clearance of the sockets and jacks. The only downside to this is that there is one large capacitor inside that obstructs the first patchbay socket of the second row from the top, and the jack plug cannot be inserted fully. This can be over come by re-positioning the capacitor on its side, just remember to discharge it first, or by omitting that socket altogether, or, just leave it as it is, put a few layers of electrical tape on top of it and promise yourself not to push anything into that socket too hard for fear of piercing the capacitor and regretting it for the next few milliseconds before death rocks up in the happy bus to take you to your new eternal home, where ever that maybe.

Remove the PCB’s and sliders from the top case before drilling, as destroying these now would be a real let down.

Using the now stuck down paper grid as a guide, drill all the holes you require, making sure they are straight and are of a suitable size for the components you are using. I find that a piece of wood underneath gives something to press against and stops the case from warping, and protects whatever surface is underneath, such as your mums nice new carpet or wooden flooring…. Thankfully I have a studio in the house so my wife doesnt care as long as the mess stays in there. Any electric hand drill will be suitable for plastic cases, but i recently invested in a nice pillar drill for such things and PCB drilling.

Here you can see the patch bay in the upper left of the panel, the 3 or 6 way multipoint bay underneath and the (unfinished) patch switches on the right.

This picture shows the inside view of the above, notice the jumper cables that were disconnected. the length of the bend point cables in this unit were a little long in retrospect, 50mm or so could have been trimmed off each, but you can see how much is required to enable easy mounting and installation of everything.

Once everthing is secured in place, re-connect the jumper cables from the front panel to to bottom half, test everything and seal it up, remembering to screw the bottom PCB back in place.

The patchbay is used by taking 3.5mm patch cables and inserting into the bay. This will connect two points of the chips that we probed, tested and soldered earlier. When a pattern is running or midi data is being received, the two connected bend points will cause an effect/bend to be generated.

To use the switches, a cables is patched from the bay, to the upper socket above the switch. another point of the bay is connected to the lower socket. When the switch is flipped, the two sockets are connected, thus completing the link between the two points of the bay and allowing you to have presets as such.

Below the bay are two sets of 3 sockets, with one switch between the two. Each set of three sockets are connected together, allowing 3 points of the patch bay to be connected for even more sonic mayhem! The switch in the middle connects the two sets, allowing them to be used independently, or combined to give up to 6 simultaneous connections. The bends generate all manner of effects, such as distortion, flanges, ring nods effects, filtering, sound swapping and muting. Some even generate synth like sounds.

The first sample here is a combination of 3 bends toggled on and off in sequence to the beats, as is the second sample, but different bend points. I added a bit of reverb, which makes the synth sounds stand out more, other than that, no external processing was done. The input connection on my old imac was a bit loose it would seem, so there’s some additional crackling in the first sample that doesnt come from the machine. Both use the same drum loop, to show the huge variation in sounds available from the bends.

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The LED schematics for the switches are a whole other story, and i’ll cover them in another tutorial at some point later, as the same principle can be used for alot of different machines. Here’s a photo of the inside, notice the use of double pole switches to allow seperate cicuits for the bends and the LED’s.