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Mopho Has Become Distorted / Noisy - Ideas?

Mopho Has Become Distorted / Noisy - Ideas?
« on: October 27, 2016, 10:21:16 AM »
Hi guys, I do have a ticket open but was wondering if any other Mopho keys users have experienced this issue.

I've had my Mopho since March 2013 and absolutely love it, which is what makes this more distressing. It's my go to synth for thick and thumping basslines, which is a huge part of my sound. In the last 2 weeks tho things have gone awry and something does not sound right. To someone who hasn't used the mopho before, they might not be able to spot it - like my huge modular nerd friend who is probably the nerdiest when it comes to synths. But to me, having recorded 3 EPs with it including 2 vinyls I know what it should sound like. It has become overly distorted and noisy, specially when the cut off and noise are cranked. Yes, the noise knob is supposed to add NOISE but it adds just white noise now, not the nice rich and piercing quality it had before which I loved, it just becomes a wall of white noise from 70 to 128 - adding no definition but almost pure white noise. I also noticed that lately when being sequenced from a DAW it would go out of tune, but this could be a separate issue... without any MIDI or USB data, the tuning seems okay, but when the cut off filter and / or noise knob are cranked there comes a point where the sound doesn't change (70 to 128 on noise knob, and  90 to 164 on cut off).

To confirm this, and to tell my friend that i'm not crazy I went to a local music store and reset their display Mopho keys with Global Reset and Compare + OSC shape calibration and went thru the basic patches, and sure enough the display mopho sounds like the rich, thumping Mopho sound i remember - and when the noise knob is cranked to max it adds a nice noise element that sounds like what I remember not what's happening with mine.

Has anyone else encountered this and does anyone have a solution? Another question - when I do Global Reset aren't the patches and saved positions in the banks supposed to factory defaults? The custom patches I made remain.

Thanks and sorry for rambling whiny post! I JUST LOVE MY MOPHO and want to cure it.

In this youtube link I included a 9 minute video with an embedded recording track that shows what I mean about the white noise issue. In general it seems my mopho has lost definition. , i also included just the 9 min mp3 here:

Thanks in advanced for any insights!!


Re: Mopho Has Become Distorted / Noisy - Ideas?
« Reply #1 on: December 20, 2016, 05:03:29 PM »

I have the Mopho Desktop, not the Mopho Keys, so it may be different, but the manual I have says there is no complete factory reset, only a Globals reset - I'd have to load the factory sounds back in, to get it back to how it was originally.

Probably the most common reason for any sort of electronic equipment to fail or degrade with age is electrolytic capacitors leaking, or failing all together.  Those are the can shaped ones.  The largest ones on the board are the most likely suspects, but any you can see are candidates for replacement.  In the case of the famous Casio DH-100 squeal problem, it's caused by a small 10uF can shaped electrolytic capacitor failing.

Leaking electrolyte can happen catastrophically (with a bang, or a puff of smoke), or just gradually, over time.  Sometimes you can see they've leaked, and maybe see deposits on the end of the capacitor or the circuit board.  Often, you can't.

You can try measuring them with a cheap capacitance meter, but measuring them in circuit won't necessarily tell you much - you may have to desolder at least one leg to get a measurement. 

The value that the meter reads can actually be higher, for a failing capacitor, because it can start to conduct, which fools the meter.  Bear in mind, that capacitor tolerances are allowed to be very high anyway - it might have been half the value marked on it from new, or at least 20% under, or it might have been 50% over.

The most reliable method is simply replacing all the electrolytic capacitors with one of the same value (in some cases its okay if it's a bit higher - e.g. for power supply smoothing), and at least the same voltage rating - if possible, go higher on the voltage rating so it will last longer.  If you don't want to replace them all, start with the largest one, then check it again to see if you still have the problem.

Of course, you may want to find a repairer to look at it for you.  I'm okay with repairing some things, but if it's expensive, or there's a lot to do, I'd consider taking it to someone else.  I had all the capacitors replaced in the power supply of my Freeview TV recorder, not long ago.  It had been getting more and more erratic over time, but that fixed it.  If you can't find a synth repairer, an open minded TV repair man might be the way to go.  They don't necessarily have to understand what they're fixing, to fix it.  Capacitor replacement is one of the things they're used to doing.


Re: Mopho Has Become Distorted / Noisy - Ideas?
« Reply #2 on: May 26, 2017, 05:49:10 PM »
Have you checked that the gain isn't getting cranked up? My keyboard did things like putting noise up in a patch spontaneously and sometimes putting the gain up. Then it would sound horribly distorted and noisy.

Might not be your problem but I don't recommend updating the OS if you follow the directions they give you it will brick it.


Re: Mopho Has Become Distorted / Noisy - Ideas?
« Reply #3 on: May 26, 2017, 07:44:57 PM »
Anyhow, I recommend you send it to DSI it costs $25 to calibrate and I'm sure they have some kind of diagnostics that can tell if something is failing.