Strange Filter Behaviour - SMR4 Mk2

Hi there : )

Built a Shruthi a few years and just recently got it out after not using it for a while.

Worked ok before but now the filter is acting very strange - I’m getting no cutoff sweep, just cuts out completely around 100 (from 127) and the oscillators are only audible if the resonance is right up, but there seems to be no actual resonant peak. The filter env mod needs to be above 4-5 to hear anything too. When I lower the cutoff, there’s no change, then just cuts out to nothing via mildly distortion. Same with lowering the res with cutoff fully open.

All other setting are initialised - amp/filter env fully open, no modulation (aside from amp - env2 on max), just one osc on a saw or squ to test etc. Tried various setting and just seems to be the filter that’s acting odd. Have also tried different PSUs with the same result.

Any ideas of a fix? Would love to get it working again, even hearing it without the filter not sure why it’s been away so long!

Thanks : )

We’re on 0.97 : )

So left it plugged in and came back to it a few hrs later, sent it a few notes and seemed to be working fairly normally (filter cutoff and res behaving almost as expected).

However after a little bit of tweaking went back to behaving weirdly as before…

Hey - sorry to bump my own thread and for my first post to be cry for help : ) not the best forum etiquette so apologies if it was rude…

Lurked the forum loads over the years, Marbles/Stages/Tides/Clouds are essentials in my rack so it’s been a great resource x

Would it be better if I posted a video or audio clip?

Thanks x

Have you tried checking where the signal path is broken, as per the troubleshooting instructions?

Intermittent faults are often caused by bad solder joints.

Thanks :slight_smile:

I’m such an amateur, built this so long ago. Should i do a visual check or use a meter?

Ah, RTFM :slight_smile:

To do the audio probe, should the top board be disconnected? Assume so as so can properly get to the point but then what’s the audio signal?

The top board should be connected, using the jumper cables that were provided with the kit.

Ok. If they came with the kits they were lost into the ether :slight_smile: I’ve got some of these, be ok? ELEGOO Multicolored Dupont Wire Kit for Arduino (120pcs) – ELEGOO Official

That’s perfect!

Great! To DIY the probe, should i just use a regular mono 1/4 jack with the cables bare one end?

Yes, that would work! The one connected to the sleeve goes to any ground point, and the one connected to the tip serves as your signal probe.

Thanks so much :slight_smile: will report back!