Enter Test Mode on Roland XV-5080 (works)

The service manual for the XV-5080 describes a wrong procedure for entering test mode. The correct method is:

  • Switch off device (if on)
  • Hold EXIT then power on device
  • Keep holding EXIT until the “SYSTEM/UTILITY” LED lights up (this takes quite a few seconds)
  • Release EXIT
  • Hold “SYSTEM/UTILITY” until “wait a moment” appears in the middle of the screen (also takes a while)

Navigate in the test mode using SHIFT+BANK and TONE buttons.

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Using Roland XV-5050 via USB MIDI on MacOS

If you want to use your XV-5050 with a newer version of MacOS, you don’t have to install a driver. The driver supplied by Roland in 2000 will not work, of course! We will use the generic class compliant USB MIDI driver. To do so, on XV-5050 press System and in MIDI&USB settings select USB Descript. Set it to GENERIC, press utility to save the settings (deactivate write protection) and reboot the synth. Check the setting again to make sure everything worked correctly.

Now you can use your Roland XV-5050 on modern Macs over USB.

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Roland XV-5050 Repair

I got a hold of a broken XV-5050. When switched on, it would only display a blank screen and that’s it, no sound, no reaction. After checking audio (no noise whatsoever), it soon became obvious that the device isn’t booting. Two reasons that were discussed on the web seemed plausible:

None of the reports above talked about a completely bricked device, however. While I was leaning toward the second hyp0thesis, I replaced the caps nonetheless, since Roland devices at that time contain notoriously bad caps (see JV-SR cap warning). As expected, the replacement didn’t help.

My assumption was that the device wouldn’t receive a proper reset signal, but that wasn’t the case. Reset was pulsed and the device should start up. So, maybe there was an unsuccessful attempt to update the firmware of the device. The JP-8080 service manual has got a particularly nice update section:

In step (7) of this procedure, if “Completed” does not appear within 40 seconds after pressing [REC] or if the message “Can’t update!” appears, then the version upgrade is a failure. When this occurs you must replace the main board.

Replace the main board if update is unsuccessful, nice!

So I put the XV-5050 in its firmware update mode (press < and > while powering up the device). And sure enough: “Update by MIDI” appeared. Finally some text! Ok, before trying that, lets check test mode (press EDIT and TONE 4 while booting). To no avail. So back to the firmware update: “Press Patch Finder”. Did it. “Error! Flash ID”.

Ah, possibly the flash chip has got problems and the device couldn’t start up properly. And in contrast to the JP-8080 Roland managed to get to two step bootstrap, so as not to break the device while updating. Nice!

The flash chip revealed bad solder joints.

Applied pressure on the the chip and yay, it starts and plays sound. Resolder. Done. Great little sounding device! But now, how do we get USB to run on Big Sur (OS X)?

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Roland XV5080, XV3080 Rotary Encoder Problem Fixed!

This week I received a nice second-hand XV3080. Everything worked fine, except the unit had the dreaded rotary encoder problem: Turning left, values decreased just fine, turning right and strange things happened. Sometimes values went up, sometimes they stayed put and sometimes they decreased!

A service manual is available, so far so good. But the actual encoder, a part from Alps is not to be had on the market. There exist some replacement tutorials, but none of them does a great job for a quick fix. My assumption is that the part just needs some cleaning…

A rotary encoder is a quite simple and purely mechanical device as you can see here, so my assumption seemed quite plausible and I also found a corresponding repair video for the Waldorf Blofeld.

So if you have the same problem, some experience with screwing 🙂 and 15 to 30 mins time: it’s an easy fix. But as always: you are responsible for your device and you are going break thinks if you have two left hands.

You cannot remove the rotary encoder cap before removing the front panel! Open the top lid and unscrew the front of the synth (see service manual). Remove the encoder cap and unscrew the PCB (Panel-A Board) to unveil the nut that is holding the rotary encoder and its PCB (Encoder Board). If you want to remove the encoder cabling from the synth you will also need to unscrew the expansion base board and then detach the 4-pin connector from the main board.

4-pin connector for the rotary encoder

Now that you have the encoder in front of you use a mini flat screwdriver to flip the ears from the metal body of the encoder. Use the inner side to get a good grip.

Straighten the metal bands so they are completely flat and then use the screwdriver (a cutter might be a better choice) to loosen the metal head from the green rest of the encoder by prying. By careful, the green plastic is quite soft and consists of multiple layers. Pry open the metal piece and detach it from the rest. Be careful to not lose any pieces or break the thin contacts.

Cleaning time: remove excess lubricant fat with the screwdriver from all parts, save it for later and clean all of the contacts carefully using contact spray and q-tips. I have also tried to carefully lift the thin sliding contacts for a higher pressure. Be very careful here! Probably thats not even needed.

Reapply the fat and assemble everything again. Works as new and didn’t take me more than 15mins with all the tools prepared. If it ain’t broken: clean it!

As to the reasons of why the encoder fails: Since there is no corrosion in the device my theory is that copper micro particles get caught in the lubricant and cause wrong pulses.

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Korg monologue Rechargable Battery Mod Prototype

My Behringer TD-3 mod worked nicely, so it was time to proceed to the monologue. It already is battery powered, but using 6 batteries and recharging done outside of the device. In my opinion a built-in single battery is more appropriate.

To see the schematic and soldering have a look at the original TD-3 post. The monologue has an even better preparation for the mod since it is built to be operated on battery and 9V, so I assume there is effective and efficient power ORing included.

On the other hand, there is less space in the device, so careful placement is key.

Resulting positioning
Li-Ion powered, USB-charged monologue

As soon as I have any numbers regarding battery life I will post an update. If you are interested in the knobs: https://ekartco.com/2020/03/korg-monologue-and-minilogue-xd-color-coding-using-chroma-caps/

The device charges and connects via USB on my iMac, so no issues here. The only thing that I need to check is power draw in standby. I assumed that batteries will get protected by KORG anyway, but the “soft” power switch might be draining too much.

My assumption in the above post was that the minilogue pulls less current than the TD-3 and the power surge at startup is not as strong. However, when the KORG is powered on and the battery is not full anymore, the same issue shows up as on the TD-3. Therefore, I will need to short the TP4056 BAT- and Vout- in just the same way as in the TD-3.


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Behringer TD-3 Rechargable Battery Mod Prototype

I love Behringer’s approach to tech and synths. The TD-3 is super affordable and performs like a charm. The community has quickly started modding the TB303 clone and I also decided to give it a simple mod: if there is something I don’t like, its cables! Also why use a 9V power wart, when there’s USB power.

I wanted to experiment with 18650 lithium ion battery cells that I will use in other contexts. The Sony 18650 VTC6 batteries that I am using deliver 3.7V on average and around 3000mAh. I would need charging electronics and then somehow try to make them deliver the 9V that the TD-3 expects.

My requirements were:

  • all components are located in the TD-3
  • battery is charged using USB or 9V while powering the device (USB preferred)
  • when unplugged, deliver 9V for the device
  • seamless plugging and unplugging (like a mobile phone)
  • enough power for a day

After some research I found the TP4056 USB charging module and MT3608 step-up converter that seem to work almost perfectly. I am picking up USB Bus (5V) and deliver the 9V at the wart connector.

Here are some pics:

TP4056, the version with protection circuit, micro USB port is unused
MT3608 with a multi-turn potentiometer to adjust Vout to 9V precisely. Turning the pot to the left multiple times will eventually show 9V on Vout.
Soldering finished
Cables fit nicely through the prepared holes
Finished battery module
Fitting room
Works like a charm: way more than ten hours of power while playing a song and powering the headphones


  • It seems that the protection circuit of the TP4056 fires when switching on the TD-3. My tests with the KORG monologue do not show that power surge. The quick fix was to short-circuit BAT- and OUT- on the TP module, since the MT3608 includes a protection module anyway. But I would like to solve this before calling it a day.
  • I am using the TP4056 OUT+/- as power delivery to the MT3608 even during charging. It works, but I suppose a better way would be to take the USB Vbus and OR it with the battery out using two Schottky diodes, or even better ideal diodes (like SM74611 with a super low loss).
  • The 9V in connector needs to be desoldered (I am not using it anymore, but it would lead to problems if anyone connects the wart…).
  • MT3608 draws power constantly (300µA) from the battery, even when the device is off. However, it should take a year to drain the battery before the undervolt protection circuit kicks in.
  • I need to test USB power draw. It worked with all chargers that I tested and my iMac.

A nice coincidence: The charging LED is bleeding softly through the function LED of the TD-3 (exaggerated in the pic), so that I can see when charging is finished (red charging/ blue fully charge):

Parts cost is less than 10$ / 10€. I found on the following offerings on amazon.de:

WARNING: This is a prototype that I built for my own testing purposes and is not finished yet. Whatever you do to your device: It is your own responsibility. Batteries are dangerous, if not handled properly!

It would be nice if Behringer offered a battery add-on (granted, not everybody needs lithium in their devices). @gekart

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Korg Monologue and Minilogue XD Color-Coding Using Chroma Caps

Today I decided for a color scheme for the Korg Monologue and Minilogue XD. Tell me what you think @gekart.


Final version on the monologue:


  • The filter knob I purchased in the standard and fat version. The fat one is a bit less tall than the others.
  • The hight of the knobs is not precisely the same, so I needed to adjust it carefully.
  • The rotary knob for program / value doesn’t fit, since the shaft in the monologue is recessed and therefore too short. I will have to prolong the knob somehow (as is done on the original knob).
  • For live performances it would be best to switch the orange and red knobs, since the orange ones glow in the dark and you probably want your cutoff to be very visible.
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Värde Utrusta Wall Cupboard Hinge 30min Fix Ikea Pro Hack

Ikea offered a nice modular kitchen in their program from end of 1990s and 2000s.

Unfortunately, they didn’t support it well. I assume it was too expensive to produce. Ikea also resorted to cheap technical solutions. For example, the 70cm wall cupboards that were available in variants with or without glas doors and in white or birch had a very poor solution to hold open the horizontal door. It was a damper that just had to fail eventually.

I replaced the damper multiple times and the replacements got quite expensive on eBay, since there were no original parts available. So, we gave up in the end: The new kitchen is in the early planning stage.

However, since I had some spare small Utrusta hinges (https://www.ikea.com/us/en/p/utrusta-small-hinge-for-horizontal-door-white-90265736/) with some research I managed to replace the dampers. This is how the result looks like, before applying finishing touches:

The most difficult part of the story is that there are no mounting holes prepared to position the hinge correctly. See the red marks in the image below to find the positioning protrusions / bolts of the hinge. We need to drill two per holes per side at the correct positions using the correctly sized wood drill (only 3mm deep!).

Pick the correctly sized drill for the protrusions. Hint: Use the pre-drilled holes of the cabinet to double-check the drill size (size is 5 in Germany, whatever that is elsewhere…).


WARNING: You should know how to drill. Apply common sense. Don’t hold me responsible, I am just describing my solution.

  • Prepare a paper template (use thick paper) with two holes, one 32mm from the top and the other at 82mm from top, both 52mm from the front (see image below).
  • Unmount the door by detaching the damper and the original hinges.
  • Hold the template to the top left and top right inner side of the cupboard and punch-mark two holes (with the wood drill, for example).
  • Drill a 3mm deep hole in each of the 4 punch-marks using a 5er wood drill. Do not apply too much pressure, you don’t want to drill a hole through the cabinet!
  • Attach the Utrusta hinge by pushing the two protrusions on the side of the hinge into the holes. If you worked precisely, the hinge should already be supporting itself.
  • From here on just follow the Utrusta mounting instructions.

And there you have it, this finally fixes the damper problem, works great with soft close and looks professional.

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Enter Docker VM on MacOS Catalina (SSH, xhyve)

As you might know, Docker containers need a Linux kernel in order to run (for Linux containers that is). So how does this work on a Mac, then, it doesn’t have a Linux kernel? Docker Desktop for MacOS will install a small Linux OS on your Mac using the MacOS-built-in xhyve hypervisor.

So if you are curious and want to poke around in Docker, you’ll need to enter the VM. Say you want to run ps on the host in order to see the individual containers running as processes, to watch how Docker images are stored or as I will show here: to see how containers are using overlay2 to merge the container filesystem with the underlying image filesystem then run this on your Mac after you started a container to get the container path:

docker inspect --format='{{.GraphDriver.Data.UpperDir}}' <container>

Now switch to the Linux VM:

screen ~/Library/Containers/com.docker.docker/Data/vms/0/tty

Then cd into the path returned by inspect. You will see the changes the container made into its filesystem or run ps to see the “real” PID of the container process.

In order to exit the VM again hit CTRL-A CTRL-\ and then y to confirm the exit.

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Xcode 11 Unable to Boot Simulator Diehard

Xcode on my Macs had a persistent problem after updating to Xcode 10: the simulators wouldn’t work anymore. Lucky me, I was busy with AWS and Kubernetes projects… Updating to Xcode 11 didn’t fix anything. Searching the web didn’t help a ton, since there seem to be many similar problems and simpler solutions, that unfortunately didn’t help at all:


The solution was to run the following command to reset the developer’s path:

sudo xcode-select --reset

Not sure if the reboot I did after that was actually necessary, but I did it anyway.

Moreover, while the installation of Xcode 11 went smoothly the update to 11.1 failed multiple times. Had to delete Xcode and reinstall cleanly. Now everything runs.

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