Horstronic Cable Tester - DIY Build
As a DIY modular enthusiast, we are always looking for ways to help improve our efficiency when we are building modules. We recently ran into an issue where upon receiving a modular kit, the power cable wasn’t included. Now, this normally wasn’t a big deal, but it was rather annoying.
With that being said, we decided why not just make cables and sell them to our customers… so thats what we did. We knew that taking this on would be a fun endeavor and we needed to ensure that our cables were fully tested to protect modules from shorting. Finally after scouring the internet for a few hours, we came across the Horstronic Cable Tester.

After reading about the Horstronic Cable Tester over on the Muffs forum we decided to order one up. There was only one problem though; there were none in stock anywhere. Stock notifications were signed up for everywhere so that we could order one up as soon as it arrived, somewhere.
A couple months had pass and then randomly we received an email that our friends over at SynthCube had a couple kits in stock…
Click, pay and sit back and wait.
A few days had passed and the full Horstronic Cable Tester kit arrived from SynthCube. To our surprise, they were the only company that made a full kit and we were thankful for that. Everywhere else had single PCBs and the components had to be sourced. Not that this is a big deal, but it’s just nice to have the kit all ready to go. It might cost a few more dollars, but at least we aren’t waiting around for components to arrive from 2-3 other places. (Shout out to SynthCube).
Let’s get onto the build shall we?
Upon unpacking the “tool”, we laid everything out, taking notice of the SMD parts that we really didn’t pay attention to when we ordered it. The description stated “hole-through” so we just figured it was hole-through components.
The PCB has a lot of surface mount resistors on the backside of the board (18 to be exact). Since we were used to SMD soldering this wasn’t a big deal and we jumped right in after laying everything out. The assembly guide was vague, but useful to say the least.
Horstronic Cable Tester Build Gallery
Before you knew it, we were done hole-through components and we moved onto the SMD. We utilized our digital microscope and this portion of the build went faster than the hole-through. Prior to just plugging it right into our rack when we were done, we took the cable tester over to your Synthrotek TST module and tested the connection of the power cable. (Since a cable was not supplied, we had to harvest one from another module we had sitting around). Everything looked good to go and it was time to utilize this amazing little tool.
One of the reasons we chose the Horstronic Cable Tester is because it is dual utility. It can also test patch cables to make sure they are working properly as well. You can test 10/16 power cables as well as 16/16 power cables. This was the perfect addition to our modular “toolbox”.
Big things in small packages….
The Horstronic Cable Tester’s size is small. Its about the size of a 1U module, and even though it looks like it would mount in a case, it doesn’t fit exact. So where do we store this thing?
Our Eurorack Passive Splitter Storage Module is the perfect place to store our new tester. It fit perfectly next to one star passive multiple. (If you don’t believe us, check out the photo to the right!)
Our Final Thoughts...
This is one utility module that will be with us for quite a long time, and it has already earned its place in our shop. One thing to keep in mind is this, even if you are not a DIY person and you do not build your own cables, the Horstronic Cable Tester is an essential tool to make sure you do not fry your modules. Let us explain… if you have one broken cable on +12V for example, that would double the resistance. One doesn’t want that, so that’s why this is checking each line individually.
The actual polarity of the LEDs is inverted on every second pin so you can see if there’s a short between cables or if the ribbon is the wrong way around. This also shows you when you have the ribbon shifted one pin on a 16-pin to 10-pin cable, which is bound to happen to you at one point in your modular journey.

In the end, we are thankful that we bought the cable tester. We NEEDED it, as we embarked on a new product to offer to our customers… eurorack power cables and flying bus boards.
Each one of our cables is assembled by hand and is tested individually to ensure that the cables do what they are supposed to do.
Although a couple of different places offer the Horstronic Cable Tester, we were thankful to finally get our hands on a “full kit” assembled by SynthCube.
If you have questions about the build process or suggestions/feedback about this article, feel free to let us know by contacting us. We look forward to hearing from you!
Until the next build …