Modular G1 - Glitchy pots

[atom_jack]

Hello all! I made some posts on Facebook about the repair process of my Nord Modular G1 25 key and someone mentioned that I should post here.

I just replaced a pot that was having problems with a new one and I’m still getting the same result; When turning the knob around 50-90%, the values begin to glitch erratically, even with the new pot. For example if I turn a frequency knob to 60%, the value will glitch between 2000Hz and 2300Hz, along those lines. The old pot I pulled even had a stable reading on the multimeter. It feels like there may be bigger problem than just the pots so I’m wondering if anyone can help point to the next step! By the way, many of the pots are like this, not just one!

I plan on taking it to a Nord authorized repair shop. If someone could recommend a shop or at home diagnostic, anything would be appreciated. Thanks!

[pterm]

Hi and welcome to the Forum!

Given the age of the a Modular G1, the power supply must be considered suspect.

Later Nord Models (e.g., Nord Electro 2) use analog to digital converters (ADC) to encode potentiometer settings. If the ADC's voltage supply, or the bias voltage supply to the potentiometer are noisy, the encoding will be erratic.

You might be able to measure noise with a handheld multimeter (if you have one). They typically can detect noise up to 1kHz - by "detect" I mean measure the DC voltage and AC voltage on the DC power supply. If noisy, the DC voltage might change instead of reading a steady value. Normally an AC measurement on a DC supply should read near 0mV. If you see an AC reading of more than 100mVAC, it suggests strongly an issue with the power supply.

One caveat: the multimeter can pick up stray 60Hz from the AC mains power supply (wall socket power), so keep the multimeter leads away from the AC power cord(s).

If this is something you want to try and need assistance let us know - I assume you replaced the pot yourself, so you have some experience with electronics repair.

[gitarrenzupfer]

Hello,

I would also strongly suspect the power supply. Perhaps you know someone who has a lab power supply and could try connecting it instead of the original one for testing. If the power supply is the problem, you could verify it quickly that way.

Regards