Roland mks-50 - LFO crackling

A guy has asked me about his mks-50, which apparently is working as it is supposed to, apart from one thing: the LFO seems to just output noise. I have not checked it up myself; before I do that, I thought I should ask Those Who Know Better Than I if this is a commonly known error. Anyone heard about this before? If the LFO is acting weird, is there anything simple one can try to replace, or is it likely due to some rare, non-replaceable IC component having exploded inside? I have tried to go through the circuit diagram of the Alpha Juno in order to understand what is going on, but it seems to be a bit out of my league…

The LFO and envelopes of the Juno are software generated. If the envelopes are fine, it is probably the DAC for the LFO that is bust. If it is on the CPU chip, you are out of luck, but the DAC should be off of the chip.

Start with the CPU, and look for a pin labeled LFO or something like modulation.

The other thing is that since all voices share an LFO, only some voices may have this LFO issue. Boot it up into calibration mode. Then play all of the voices with a lot of LFO on them. See if any don’t have the noise issue.

Maybe try sending a high mod wheel amount to the unit too before doing anything drastic.

@audiohoarder: Thanks a lot! Now we have something to start with. Now I’ll just find the time to try these things…

@thhmas Posting a recording of the crackling along with the patch that causes it will also be helpful. I have a perfectly working MKS-50 here so i can compare how it sounds.