Issue with 2164 VCA Build


I’ve just completed building all 3 Electrosmith eurorack modules. Filter works great and tracks nicely over a few octaves. VCO is fully functional (although I’ve not tried calibration yet). But the VCA sends my power supply into an odd state when I plug it in and power on my case (kinda borks my whole system). I’m using a Trogotronic M15 4x104hp PSU and am nowhere near using all the power. I’ve also tried plugging into different bus boards on my case and also different power cables but the result is always the same.

Any advice would be appreciated.

Thanks in advance!

Just a guess, but it sounds like a wiring error causing a short and therefore the power supply issue. If you have a multi-meter measure the resistance between the power leads when not hooked up to see if it is very low, like a few ohms - that would cause the symptoms you reported.

Thank you for your reply! Just to clarify - since there was no wiring involved with this build, are you recommending I check the resistance between pins on the power header of the unplugged module?

Correct. And compare it to a good module - even if it’s not the exact same module, the measured resistances should be similar magnitude. If you see a very low resistance (like 2 or 3 ohms) between the power lead and ground, that could be the problem.

I thought these modules were kits, and I guess the “no wiring” on your part makes it less likely, but in my opinion, still possible that the board has some kind of short and that’s why it upsets your power supply.

You are correct - these modules are kits. I’ll check this tonight and post back.

I meant any type of error on the board - could be an excess solder blob connecting two points that shouldn’t be connected, or a component which has ‘polarity’ (electrolytic caps, diodes, ICs, etc.) inserted in the wrong direction or something else.

OK, so here are the results of my testing:

On the VCA module (the bad one): +12V to ground is about 1.15kOhms, -12V to ground is about 320kOhms.

On a good module: +12V to ground is about 4.1kOhms, -12V to ground is 0.4MOhms.

I took apart the VCA module, inspected all of the solder joints, particularly those on the power header and even reflowed those as a precaution but no change.

It’s frustrating because these are the simplest modules I’ve ever built. Just pots, jacks and LEDs on one side of the board, with the 2164 VCA submodule on the back. I’m wondering if the submodule is faulty.

Thank you again for your assistance!

Interesting, it doesn’t seem like a ‘short’, and I don’t know if the 1.15k is just normal for a 2164 module. It would be nice if some kind soul could measure a good 2164 for you to compare.

The word ‘module’ is ambiguous here - the complete Eurorack module, or the 2164 module which is installed on the Eurorack module?

I’d test for shorts on the Eurorack module, with and without the 2164 module installed. I’d be checking +12 to ground, -12 to ground, and +12 to -12. And I’d try to power it up in the Eurorack case without the 2164 installed.

It might just be a defective 2164 module.

Great point tele_player! Use of the word ‘module’ is confusing here. To clarify, I used module to mean the completed eurorack module and submodule to mean the 2164 VCA submodule.

I’ll take new voltage readings with/without the submodule installed tonight and also plug the eurorack module into power without the submodule attached and see if it still affects my entire system.

If it is a defective submodule, I may be out of luck as all of these eurorack modules appear to be considered legacy product on the Electrosmith website.

Please keep me posted about this. I will talk to the team to see what we can do.

OK - here’s the latest…

With the 2164 VCA Submodule installed:
+12V to Ground I get 1-4 kOhms, -12 to +12 is 263kOhms and -12V to Ground fluctuates between 26kOhms and open (OL) which make sense given that when I plug in this eurorack module and power up I get flashing lights on the bus boards for my PSU and some modules flashing.

Without the 2164 VCA Submodule installed, all resistance the readings I took above are OL. Also plugging in the eurorack module without the VCA submodule installed and powering on does not affect my system (i.e. power bus board lights are not flashing and all other modules function properly).

Could you contact us about the VCA module when you get a chance? Please include the issue you’re facing with it, the order number, and etc. Thanks!

If it ends up being that it was something faulty, then we can go through an RMA.

Contact form submitted.

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