Eurorack module testing tool (DIY)


There should be a DC jack and an AC jack so this confusion doesn’t happen. I popped a voltage regulator on a Nintendo NEC toploader thinking the UK NES and the toploader would use the same voltage.


That was it; works like a charm now. Thanks to everyone for their help - and to Olivier for making this open and awesome!

6581punk: sounds very reasonable - especially to me. :slight_smile:




bpc - i’m in hollywood - anything in particular you needed assistance with?


Just want to say thanks to Olivier for open sourcing his work!
I finished building the tester today. It’s the first time everything worked at the first try for me (apart from some problems with a missing TO-220 heatsink from Mouser)!
The hardest part was to find a 12VAC supply. In the end I found some old IKEA halogen lamp transformers in a junk drawer.


I am in a soldering spree and next is Eurorack tester.

Will this be OK powering tester ?
What size led spacers must I use ? as I am planning for laser cut enclosure


Just use the front panel, install the standoffs, drop the leds into the board, install the board, led the LEDs drop in their respective holes…



I have built the module tester. However the display’s first line all the pixels are lit. Turning the encoder some times they all go out. The switches and leds all function. The voltages are all good. I get sine, triangle square etc out of the audio out jack.

Any ideas what might be wrong?


Have you adjusted the LCD contrast pot?

If that doesn’t do it, try reflowing the solder of the display header.



Thx Toneburst,

I checked the contrast pot and reflowed the display header, no change.



This is what the display looks like, (not my display but a picture of one behaving in the same way.
Cant figure why, could it be a software issue?


I think it’s more likely your issue is hardware related, have you checked all your solder joints? Everything polarized is in the correct direction?


Thanks DMR,

I checked all the polarized components and joints they are ok.

i checked the voltages on the 2x16 display
VSS is ground
VDD is 5 volts
VOo is about 0.6 volts contrast
RS reads 0.006 volts
the circuit diagram has a +5 by the RS pin

Could this be the problem?



As I select other switches and rotate the encoder the display occasionally goes totally blank or the first line all on???


The display shows this type of image when its not initialized. This can mean the processor is not running or the soldering on the pins connecting it to the display is bad.


Yet if audio / cv is being generated it suggests that the processor is okay.


I was wondering, for the others that built this awesome testing tool: When you calibrate the CV Out voltages (1V and 3V on 2 Octave Arp) how close are you able to get them?

The closest I can seem to get is 1V and 3.04V.
I was wondering, is that close enough?

Is there a preferred way to calibrate? Such as adjust R13 first, then R9, et cetera.

Thanks in advance for any assistance.


Calibration and references is always a tricky business. It depends on what you want to test. It’s probably good enough. If it’s not you should not have asked :wink:


> The closest I can seem to get is 1V and 3.04V.

You mean you have reached the end of the trimmer and cannot reduce the scale?


>You mean you have reached the end of the trimmer and cannot reduce the scale?



That’s odd, I guess you’d have to change the resistor and trimmer to get a larger range: R12 for 39k and R13 for 20k.